Herpetofaunal Inventories of the National 

Parks of South Florida and the Caribbean: 

Volume IV. Biscayne National Park

By Kenneth G. Rice1, J. Hardin Waddle1, Marquette E. Crockett 2, 

Christopher D. Bugbee2, Brian M. Jeffery 2, and H. Franklin Percival 3

1U.S. Geological Survey, Florida Integrated Science Center

2University of Florida, Department of Wildlife Ecology and Conservation

3 Florida Cooperative Fish and Wildlife Research Unit

Open-File Report 2007-1057

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2007

For product and ordering information:

World Wide Web: http://www.usgs.gov/pubprod

Telephone: 1-888-ASK-USGS

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce 

any copyrighted materials contained within this report.

Suggested citation:

Rice, K.G., Waddle, J.H., Crockett, M.E., Bugbee, C.D., Jeffery, B.M., and Percival, H.F., 2007, 

Herpetofaunal Inventories of the National Parks of South Florida and the Caribbean: Volume IV. 

Biscayne National Park: U.S. Geological Survey Open-File Report 2007-1057, 65 p.

Online at:

http://pubs.usgs.gov/ofr/2007/1057/

For more information about this report, contact:

Dr. Kenneth G. Rice

U.S. Geological Survey

Florida Integrated Science Center UF-FLREC

3205 College Ave.

Ft. Lauderdale, FL 33314 USA

E-mail: ken_g_rice@usgs.gov Phone: 954-577-6305 Fax: 954-577-6347

Dr. J. Hardin Waddle

Florida Cooperative Fish and Wildlife Research Unit

Box 110485, Building 810

University of Florida

Gainesville, FL 32611 USA

E-mail: hardin_waddle@usgs.gov Phone: 352-846-0638 Fax: 352-846-0841

Cover photo: Cuban treefrog
Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Methods...........................................................................................................................................................3

Site Selection.........................................................................................................................................3

Visual Encounter Surveys....................................................................................................................3

Anuran Vocalization Surveys..............................................................................................................4

Additional Sampling..............................................................................................................................4

Data Analysis.........................................................................................................................................5

Results ....................................................................................................................................................6

Acris gryllus..................................................................................................................................7

Bufo marinus.................................................................................................................................7

Bufo terrestris...............................................................................................................................8

Eleutherodactylus planirostris...................................................................................................8

Gastrophryne carolinensis.........................................................................................................9

Hyla cinerea..................................................................................................................................9

Hyla squirella..............................................................................................................................10

Osteopilus septentrionalis........................................................................................................10

Rana grylio ..................................................................................................................................11

Rana sphenocephala ................................................................................................................11

Reptiles.................................................................................................................................................11

Conclusions...................................................................................................................................................12

Acknowledgments.......................................................................................................................................13

References....................................................................................................................................................14

Appendix I. Best models of proportion area occupied by species ..............................................63-64

Appendix II. Biscayne National Park website list of reptiles present in the park ............................65

Figures

 1-3. Maps showing: 

1. Southern Florida, showing location of Biscayne National Park ................................. 17

2. Biscayne National Park...................................................................................................... 18

3. Four major habitats within Biscayne National Park...................................................... 19

 4-5. Maps showing sampling locations in Biscayne National Park where visual 

 encounter surveys and vocalization surveys were conducted during this study:

4. At least twice at 37 sites..................................................................................................... 20

5. On a monthly basis at 16 sites ........................................................................................... 21

 6-29. Maps showing locations in Biscayne National Park where the following species 

 were observed:

6. Acris gryllus .......................................................................................................................... 22

7. Bufo marinus......................................................................................................................... 23

8. Bufo terrestris....................................................................................................................... 24

9. Eleutherodactylus planirostris .......................................................................................... 25

10. Gastrophryne carolinensis................................................................................................. 26

11. Hyla cinerea.......................................................................................................................... 27

iii
12. Hyla squirella........................................................................................................................ 28

13. Osteopilus septentrionalis.................................................................................................. 29

14. Rana grylio ............................................................................................................................ 30

15. Rana sphenocephala .......................................................................................................... 31

16. Alligator mississippiensis................................................................................................... 32

17. Crocodylus acutus............................................................................................................... 33

18. Anolis carolinensis .............................................................................................................. 34

19. Anolis sagrei......................................................................................................................... 35

20. Eumeces inexpectatus........................................................................................................ 36

21. Hemidactylus garnotti......................................................................................................... 37

22. Hemidactlyus mabouia ....................................................................................................... 38

23. Sphaerodactylus notatus ................................................................................................... 39

24. Diadophis punctatus ........................................................................................................... 40

25. Elaphe guttata....................................................................................................................... 41

26. Elaphe obsoleta.................................................................................................................... 42

27. Nerodia clarkii...................................................................................................................... 43

28. Nerodia fasciata .................................................................................................................. 44

29. Ramphotyphlops braminus ................................................................................................ 45

Tables

1. Vegetation classification of Key Biscayne National Park .........................................................49-50

2. The 14 models evaluated for most amphibian species to determine the estimate of proportion 

of area occupied and detection probability ...................................................................................... 51

3. Location, number of visits, and habitat type of sampled sites....................................................... 52

4. Amphibian detection in vegetation classification............................................................................ 53

5. Amphibian average proportion of area occupied estimate comparisons................................... 53

6. Number of individuals captured and number of site visits when at least one of each 

species was heard vocalizing out of 236 possible samples........................................................... 54

7. Months in 2003 when individuals were detected by visual encounter survey methods 

and by vocalization ................................................................................................................................ 55

8. Results of proportion of area occupied analysis for Acris gryllus................................................ 56

9. Contribution of four different variables to the occupancy model selection of six 

amphibian species ................................................................................................................................. 56

10. Results of proportion of area occupied analysis for Bufo marinus .............................................. 57

11. Snout-to-vent length of amphibian species captured in Biscayne National Park..................... 57

12. Results of proportion of area occupied analysis for Eleutherodactylus planirostris ................ 58

13. Results of proportion of area occupied analysis for Hyla cinerea ............................................... 58

14. Results of proportion of area occupied analysis for Osteopilus septentrionalis ....................... 59

15. Results of proportion of area occupied analysis for Rana sphenocephala................................ 59

16. Reptile species observed during amphibian inventory in Biscayne National Park 

during 2002-2003 and method of detection........................................................................................ 60

iv
 Conversion Factors, Acronyms, and 

 Abbreviations

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

meter (m) 1.094 yard (yd) 

Area

square meter (m2

) 0.0002471 acre 

hectare (ha) 2.471 acre

AIC Akaike’s Information Criterion

BISC Biscayne National Park

CI Confidence interval

PAO proportion of area occupied

SD standard deviation

SE standard error

SVL snout-to-vent length

UTM Universal Transverse Mercator

VES visual encounter surveys 

WGS World Geodetic System

v

Abstract

Amphibian declines and extinctions have been documented around the world, often in protected 

natural areas. Concern for this alarming trend has prompted the U.S. Geological Survey and the National 

Park Service to document all species of amphibians that occur within U.S. National Parks and to search 

for any signs that amphibians may be declining. This study, an inventory of amphibian species in 

Biscayne National Park, was conducted during 2002 and 2003. The goals of the project were to create 

a georeferenced inventory of amphibian species, use new analytical techniques to estimate proportion 

of sites occupied by each species, look for evidence of known stressors or problems that may lead to 

amphibian population decline (invasive species, disease, die-offs, and so forth), and to establish a baseline 

and methodology that could be used for future monitoring efforts.

Four sampling methods were used to accomplish these goals. Visual encounter surveys and anuran 

vocalization surveys were conducted during 236 visits to 37 sites in all habitats throughout Biscayne 

National Park to estimate the proportion of sites or proportion of area occupied (PAO) by each amphibian 

species in each habitat. More than 100 individuals of 7 amphibian species were detected during standard 

sampling, and 24 individuals of 6 species of amphibians and 37 individuals of 12 species of reptiles were 

encountered during opportunistic collections and nighttime road surveys used to augment the visual 

encounter methods for more rare or cryptic species. The software PRESENCE was used to provide PAO 

estimates for each of the anuran species based on the visual encounter surveys and anuran vocalization 

data.

Amphibian species (six native and three non-native) were documented in Biscayne National Park 

during this project. The PAO estimates obtained for the six most common amphibians will serve as a 

comparative baseline for future monitoring efforts. Although 14 non-marine reptile species were detected 

during this study, PAO for reptile species was not estimated because there were too few encounters during 

this study. The methods used in this study are adequate to produce reliable estimates of the proportion 

of sites occupied by most anuran species. Therefore, future sampling at regular intervals could be a 

cost-effective way of following amphibian occupancy trends.

 

Herpetofaunal Inventories of the National Parks of 

South Florida and the Caribbean: Volume IV. 

Biscayne National Park

 

By Kenneth G. Rice, J. Hardin Waddle, Marquette E. Crockett, Chris Bugbee, Brian M. Jeffery, 

and H. Franklin Percival
2 Herpetofaunal Inventory of Biscayne National Park

This study identified some threats to amphibians in Biscayne National Park, especially introduced 

species, such as the Cuban treefrog (Osteopilus septentrionalis), the marine or cane toad (Bufo marinus), 

and the greenhouse frog (Eleutherodactylus planirostris planirostris) that were collectively detected 

nearly three times as often as native species. 

Introduction

Declines in amphibian populations have been documented worldwide from many regions and 

ecosystems (Alford and Richards, 1999). No single cause for declines has been demonstrated, and it 

seems probable that several factors may interact to threaten populations (Carey and Bryant, 1995). 

A major factor in the loss of amphibian populations in the southeastern United States continues to be the 

loss of habitat (Dodd and Cade, 1998). In response to concerns about amphibian population declines, 

the Department of Interior instituted long-term surveys of the status and trends of amphibians on its 

lands (U.S. Geological Survey Amphibian Research and Monitoring Initiative and National Park Service 

Inventory and Monitoring Network). Baseline inventories of amphibian species were conducted across 

the Nation; this document describes an inventory of the amphibians of Biscayne National Park (BISC) 

conducted during 2002 and 2003.

BISC (http://www.nps.gov/bisc) protects over 70,010 hectares of aquatic and terrestrial habitat 

located on the mangrove-lined southeastern coast of Florida, south of Miami and east of Homestead in 

Miami-Dade County (figs. 1 and 2). Although BISC is primarily an aquatic park protecting bay and reef 

habitats, the park contains non-aquatic habitats consisting of several small islands and coastal areas of the 

mainland which total less than 5 percent of the park. The islands are part of the upper chain of the Florida 

Keys, and are located between Key Biscayne to the north and Key Largo to the south. Terrestrial habitats 

in BISC consist primarily of mixed mangrove forests and tropical hardwood hammocks. 

Duellman and Schwartz (1958) produced the first complete species list of the herpetofauna of 

south Florida. Not every species listed as an inhabitant of south Florida is represented in BISC, presumably because of the limited habitat types. Most of the terrestrial habitat in BISC is naturally saline and 

lacking in permanent freshwater. Only a small percentage of amphibian and reptile species that are 

present in south Florida are tolerant of, or adapted to, the saline environments in the park. Because a 

systematic inventory of the herpetofauna of BISC has never been conducted, the first objective of this 

study was to document all species of amphibians and, opportunistically, reptiles in the park. 

In addition to providing a sample of georeferenced locations of all amphibian species in BISC, this 

study enabled researchers to provide baseline information for future monitoring of amphibian status in the 

park. The validation of the baseline information was accomplished with detection/non-detection data from 

repeated sampling at randomly selected sites throughout BISC, using the site occupancy estimation model 

developed by MacKenzie and others (2002). This method can serve as an index of abundance, and can be 

compared to future samples to determine trends in the status of amphibian populations. Similar sampling 

and analysis methods were employed in related projects in Everglades National Park and Big Cypress 

National Preserve (Rice and others 2004, 2005). The methodologies developed in this study represent 

efforts to adaptively establish a protocol for future monitoring of amphibians in the park.
Methods

Data for amphibians and reptiles were collected using several methods at sites throughout BISC 

in an attempt to identify species presence. Standard sampling at randomly selected sites stratified by 

habitat included both visual encounter surveys (VES) and vocalization surveys. Other sampling included 

road cruises and visits to specific sites to search for other species. Opportunistic encounters with amphibians and reptiles were noted with details on the exact location of the capture and data on each individual 

animal. 

Site Selection

Sampling sites were selected randomly throughout BISC using a geographic information system 

(GIS), and all sampling was stratified by major habitat type. The park was divided into four natural 

habitats: hammock (primarily buttonwood forest), mangrove (dominated by red mangrove, but including 

black and white mangrove), prairie (dominated by graminoid plants), and mangrove scrub (dominated 

by red mangrove scrub) (fig. 3). Natural habitat designations were created by condensing the vegetation 

classification scheme proposed by Madden and others (1999) into four broader habitat categories (table 

1). Artificial habitat (disturbed areas significantly altered by humans) was also sampled. Opportunistic 

encounters were used to sample some structures, such as buildings, roads, and canals. 

ArcView® 3.2 was used with the Animal Movement Analysis extension (Hooge and Eichenlaub, 

1997) to randomly select sites within each major natural habitat type. More random sites were created 

than could be sampled, so sites were selected from the list of available sites for sampling based on 

availability of access. For example, if the next random site within a habitat was deemed inaccessible 

(no boat access, no road access, or extremely thick vegetation) after an attempt was made to visit it, 

the next random site was selected. Some parts of BISC were inaccessible by the means available to the 

technicians (particularly much of the southern mainland area), but all designated habitats in BISC were 

sampled throughout the course of this study. Every habitat was sampled for 12 consecutive months during 

August 2002 through July 2003. The number of sampling occasions per site was variable. A total of 

37 sampling sites were established with 16 sites sampled monthly and 21 sites sampled at least twice. 

Repeated sampling at a subset of the more accessible sites was an efficient way to estimate habitat-level 

occupancy rates, although less frequent sampling at more remote locations provided better data on species 

distribution within BISC. 

Visual Encounter Surveys

The primary method of sampling was a standard VES (Heyer and others, 1994) conducted for 

30 minutes at the randomly selected sites. All VES samples were begun at least 30 minutes after sunset 

because preliminary surveys in Everglades National Park indicated that amphibians were more active 

and more easily detected at night (Rice and others, 2004). Each VES was conducted by at least two 

experienced observers using powerful 6-volt lights with halogen bulbs.

Methods 3
4 Herpetofaunal Inventory of Biscayne National Park

The VES samples were all within a 20-meter radius circle of the randomly selected site, an area 

of 1,256 square meters. Observers used their own judgement to stay within 20 meters of the center of 

the circle. Each circular plot was searched as thoroughly as possible in the time allotted and all areas 

were covered at least in passing, however, observers determined which areas within the plot were most 

emphasized. The goal was to find as many individual amphibians as possible; amphibian locations that 

could be searched included trees and other vegetation as well as bare ground and leaf litter. 

An attempt was made to capture each individual amphibian and reptile that was observed during 

a VES. The animals were identified to species and sex, if possible, and the age/life stage (juvenile, adult, 

larva, and so forth) was recorded. The snout-to-vent length (SVL) of each animal captured was measured 

in millimeters, and the substrate and/or perch height (estimated to the nearest 10 centimeters) where each 

individual was first observed was noted. 

In addition to the biological data collected during a VES, some key environmental data were 

collected in the field at the time of the survey. Air temperature and relative humidity were measured using 

a Spectrum Technologies, Inc. 3411WB digital thermohygrometer. Water temperature was measured and 

recorded if the plot was inundated. The weather was noted and classified into one of five categories: clear, 

partly cloudy, cloudy, rain, or fog. Wind speed was classified as none, light, moderate, or strong. The 

date and time of the sample and the names of the observers were also recorded. All data were recorded 

on personal digital assistants and later transferred to a Microsoft® Office Access database (Waddle and 

others 2003).

Anuran Vocalization Surveys

During a VES, all of the species of frogs and toads that were heard vocalizing during a 10-minute 

period were noted at each plot site. All anurans that could be heard were included, even if it was possible 

or likely that they were calling from a location outside of the 20-meter radius plot site. The need to locate 

vocalizing individuals was eliminated by including all individuals heard, which facilitated comparison 

with similar surveys conducted elsewhere.

The abundance of vocalizing individuals was estimated and classified in one of five categories: 

1 individual, 2-5 individuals, 6-10 individuals, more than 10 individuals, or large chorus. The frequency 

of calling by each species was categorized as occasional, frequent, or continuous. These categories were 

discussed with newer observers in the field so that a consensus could be reached on which category to 

place the abundance and frequency of calls.

Additional Sampling

Additional sampling consisted of nighttime road surveys and opportunistic observations. Road 

surveys were used in addition to the standard sampling previously described to attempt to fully document 

the amphibian and reptile fauna of BISC. Most of this sampling was performed to augment the species 

list. Data from this additional sampling were only included in the list of species detected and their 

locations. Because sites were not randomly selected and sampling effort was not consistent, these data 

were not compatible with the proportion of sites occupied analysis technique used for the VES and 

vocalization surveys (see Data Analysis section).
Data Analysis

Detection probabilities for all amphibian and reptile species were assumed a priori to be less than 

one. Therefore, data were collected in a method compatible with the site occupancy model of MacKenzie 

and others (2002). This method estimated sampling occasion specific detection probabilities for each 

species using maximum likelihood statistical techniques. By estimating detection probabilities, it was 

possible to estimate the true site occupancy rate of each species by habitat, while taking into account the 

effects of environmental variables on the behavior of the animals. Detection rates were not assumed to 

be constant across species, habitats, time, or environment. However, if a species was present, a detection 

probability greater than zero was assumed. Also, sites were assumed to be closed to changes in occupancy 

between subsequent samples. Therefore, only data from surveys that were conducted within 6 months of 

one another were considered. 

This site occupancy model, when applied to randomly selected sites in a defined area, was used 

to represent an estimate of the PAO by a species. This number was not an estimate of the abundance 

of individuals, but rather an estimate of the proportion of randomly selected sites that were expected 

to be occupied by a given species. Because this model was based on repeated sampling and maximum 

likelihood techniques, it produced a robust estimate with a measure of precision that can be compared to 

similar estimates obtained in other studies, including future monitoring of the same area.

All data were compiled in Microsoft® Office Access and then extracted as capture histories for 

analysis in the program PRESENCE (MacKenzie and others 2002). The detection data were too sparse 

to provide enough power to estimate habitat level occupancy rates, but, whether or not the site was on an 

island or the mainland was used as a site-specific covariable in the analysis. Variables that affect detection 

probability (p) were sampling occasion covariables: air temperature, relative humidity, and presence of 

standing water. For each species, 14 models were considered that were combinations of those variables 

that were determined to be biologically meaningful a prior (table 2). As an example, the full model:

Psi(island); p(temp, humid, water)

estimated PAO (psi) as a function of the variable island (0=mainland, 1=island) and detection probability 

(p) as a function of temperature (degrees Celcius at time of survey), relative humidity (percent at time of 

survey), and presence of standing water (0=no water, 1=water present in plot). The model:

Psi (.); p(.)

estimated psi as a constant across all habitats and detection probability as a constant across all visits.

From MacKenzie (2002), the logistic model was required to relate covariates to occupancy and 

detection probabilities, such that:

Psii = β0 β1Xi exp( ) +

1 β0 β + 1Xi + exp( ) ----------------------------------------------

pij

β0 β1Xi β2Y + + ij exp( )

1 β0 β1Xi β2Yij + exp( ) + + = -----------------------------------------------------------------

Where Xi was a site specific covariate for site i, and Yij was a sampling occasion covariate for site 

i and time j. β0 was the intercept term for the model, whereas β1 and β2 were the coefficients for the 

covariates. Therefore, in the example of the full model above:

Methods 5
6 Herpetofaunal Inventory of Biscayne National Park

Psi (island) = β0 β + 1 exp( )

1 β0 β1 + exp( ) + -----------------------------------------

Psi (mainland) = β0 exp( )

1 β0 + exp( ) -----------------------------

The best model was the one with the lowest value for Akaike’s information criterion (AIC), 

the most parsimonious model or the model with the best fit for the fewest parameters (Burnham and 

Anderson, 1998). This method of model selection allowed determination of the most important factors 

in sampling for individual species, and enabled selection of the best estimate of the site occupancy of 

each species. Generally, models with AIC values within two units of the best model were considered 

reasonable alternatives.

Overall site occupancy estimates were averaged across models weighted by AIC weights to 

produce the best estimate of the true PAO (Burnham and Anderson, 1998). Based upon AIC values 

(MacKenzie, 2002), the weight for the jth of the m models fitted to the data, wj, was

wj

∆AICj exp( ) –

∆AICk exp( ) – k =1

m

∑

= --------------------------------------------

where ΔAICj was the difference in AIC between the minimum value and the value for model j (Burnham 

and Anderson, 1998). Model averaged estimates of the parameter (λ) and associated standard error (SE) 

were (Burnham and Anderson, 1998):

–

γ wj

j =1

m

∑ λ

ˆ

j =

SE( ) λ wj

j =1

m

∑ SE λ

ˆ

( )j

2 λ

ˆ

( ) j – λ 2 = +

Results

The study included a total of 236 standarized sampling visits to 37 project sites (fig. 4). Of the 

37 sites that were visited at least twice, eight amphibian and eight reptile species were encountered. Two 

to seven sites in each habitat were sampled monthly (fig. 5), and one to twelve sites in each of the other 

habitats were also visited (table 3). The largest number of visited study sites (19) was in mangrove habitat. 

An additional amphibian (one additional species was found just outside BISC boundary) and 

six reptiles were observed by opportunistic encounters and road cruises. Therefore, the total number of 

amphibian species documented in BISC during this study was nine, and the total number of documented 

reptile species in BISC was fourteen.
Specific capture information (table 4) and PAO model results (table 5) are presented in the 

following species descriptions. Appendix I presents β i values for covariates present in the best model as 

determined by AIC. The best model is determined to be the most accurate, given the set of models and 

the data. Although the best model minimized AIC, in some cases the SE’s of the covariates are not useful 

for prediction. These results can be useful in determining the relationship between a covariate and the 

appropriate parameter. The most important use of the PAO results is as a baseline for future monitoring of 

these species.

During the study, researchers were prepared to collect specimens suspected of disease or other 

health problems and provide them to the U.S. Geological Survey National Wildlife Health Center for 

diagnosis. However, no individuals were suspect.

Acris gryllus

The Florida cricket frog (Acris gryllus dorsalis) is not common in BISC. Cricket frogs were 

detected in mangrove and mangrove scrub habitat within the park during vocalization surveys, where they 

were heard on 6 of 236 sampling occasions at a total of 4 locations (fig. 6, table 6). Three of the locations 

were on the mainland, but one site was on Elliott Key. Cricket frogs were detected solely by vocal surveys 

in March and again in May through August (table 7).

The naïve, or minimum, site occupancy for the species was 10.8 percent overall. The model-averaged PAO estimate for cricket frogs was 35.0 percent (SE = 0.2096) occupancy of all sites within the park. 

The best model for site occupancy estimation included only island as a site covariate and no detection 

covariates, but several other models had weights (table 8). Island had the greatest variable contribution 

(0.55) to the model selection, followed by the presence of ponded water (0.30), air temperature (0.23), 

and relative humidity (0.18) (table 9). Occupancy rates were estimated as 8.6 percent (SE = 0.12) at island 

sites and 60.3 percent (SE = 0.39) at mainland sites. 

Cricket frogs appear to be restricted to the mainland and Elliott Key within the park. Cricket frogs 

are aquatic species usually found in association with permanent water (Conant and Collins, 1991), so it is 

unlikely that the species could survive on the other drier islands. Cricket frogs must also be limited in area 

on Elliott Key due to the lack of wet sites. BISC probably provides only marginal habitat for cricket frogs, 

although they are abundant throughout peninsular Florida.

Bufo marinus

The marine or cane toad (Bufo marinus) is a non-native species in Florida. It was first introduced 

into Miami-Dade County in the 1950s as a control for agricultural pests, but probably did not become 

established until subsequent releases of marine toads kept as pets (Meshaka and others, 2004). During 

the study, they were heard calling in every natural habitat within BISC and on 31 of 236 visits (table 6). 

Marine toads were observed on the mainland and on five of the six islands sampled (fig. 7). Vocalizations 

were heard from February through August and again in October and December (table 7). This species 

appears to be active throughout the year in south Florida.

Results 7
8 Herpetofaunal Inventory of Biscayne National Park

The naïve, or minimum, site occupancy for marine toads was 37.8 percent across all sites, and 

the model-averaged PAO estimate was 77.9 percent (SE = 0.1499) occupancy of all sites within the park. 

The best model for site occupancy estimation included no site covariate and only humidity as a detection 

covariate, but several other models had weights (table 10). Island had a relatively low variable contribution (0.18) to the model selection, and the presence of ponded water (0.25), air temperature (0.41), and 

relative humidity (0.50) were all higher (table 9). Occupancy rates were estimated as 16.3 percent (SE = 

0.82) at island sites and 93.3 percent (SE = 0.38) at mainland sites. 

No marine toads were found within BISC during VES, but they were observed during opportunistic encounters. The best method for detecting this species appears to be listening for vocalizations. 

Humidity may be an important factor in determining when marine toads will vocalize. Because they were 

detected on so many different islands underscores the dispersal capabilities and the resiliency of this 

invasive species. 

Bufo terrestris 

The southern toad (Bufo terrestris) was detected on only one occasion in an opportunistic 

encounter in August 2003 just outside BISC boundary (fig. 8). This individual was found on a levee 

separating a canal habitat and a mangrove scrub habitat. No evidence of this species was detected during 

the standard VES or vocal surveys. Detection rates for southern toads were low in Everglades National 

Park (Rice and others 2004), and it is likely that this species is difficult to detect outside of the breeding 

season. 

Eleutherodactylus planirostris

The Greenhouse frog (Eleutherodactylus planirostris) was found in BISC (fig. 9). Greenhouse 

frogs were heard vocalizing on 26 of 236 visits to BISC (table 6). Vocalizations were concentrated 

between May and September. This period corresponds to the summer rainy season. During VES searches, 

38 greenhouse frogs were found within BISC (hammock, mangrove, and mangrove scrub habitats). These 

frogs were found throughout the year (table 7), which indicates that they are active year round in south 

Florida. Based on the data collected during this study, either visual or vocal surveys are viable methods 

for monitoring greenhouse frogs. However, vocal surveys would be most effective during the rainy season. 

SVL lengths of greenhouse frogs ranged from 11-23 millimeter (mm) with a mean of 19.33 mm (±4.32 

SD) (table 11).

The naïve, or minimum, site occupancy for greenhouse frogs was 37.84 percent overall, and the 

model-averaged PAO estimate was 54.4 percent (S. = 0.1077) occupancy of all sites within the park. The 

best model for site occupancy estimation included island as a site covariate and only air temperature as a 

detection covariate, but several other models had weights (table 12). The air temperature variable had the 

greatest contribution (0.99) to the model selection, and island (0.69) and relative humidity (0.49) were 

also high (table 9). The presence of standing water had the lowest variable contribution (0.21; table 9). 

Occupancy rates of greenhouse frogs were estimated as 87.6 percent (SE = 0.107) at island sites and 29.7 

percent (SE = 0.152) at mainland sites.

Greenhouse frogs are well established in BISC. They appear to be most abundant and widespread 

on the islands in the park and are possibly the most widespread of the three established exotic anurans 

in south Florida. Because greenhouse frogs are direct-developing frogs with terrestrial nests, it is not 

surprising that they are able to thrive where there is a lack of freshwater. This may also explain why 

standing water was relatively unimportant for model selection. 
Gastrophryne carolinensis 

Eastern narrowmouth toads (Gastrophryne carolinensis) were not encountered using VES or vocal 

surveys. However, there were three instances of narrowmouth toads in opportunistic encounters, one in 

August 2002 and two in March 2003. These observations occurred on Elliott Key (fig. 10), and multiple 

individuals were seen in each case. In March 2003, a large chorusing aggregation was observed on two 

consecutive nights after a heavy rain. These frogs were encountered on a small road in mangrove habitat. 

Only one narrowmouth toad was captured during this study. This individual had a SVL of 30 mm, which 

is within the normal range of the species. No estimates of site occupancy are possible for narrowmouth 

toads in BISC due to the lack of encounters during standard sampling.

Eastern narrowmouth toads and cricket frogs are the only native frogs found on any of the islands 

in the park. It is not clear whether this is because of the high dispersal ability in these species or if it is a 

function of the habitat requirements. Narrowmouth toads could be somewhat tolerant of salinity in water, 

because they were commonly encountered in mangrove habitats in Everglades National Park (Rice and 

others, 2004). In addition to the introduced species and the cricket frogs, narrowmouth toads might be 

able to reproduce in extremely ephemeral bodies of water. In either case, the freshwater puddles on Elliott 

Key represent an important resource for frogs. 

Hyla cinerea

The green treefrog (Hyla cinerea) was the third most commonly observed amphibian species 

in the park. All observations of this species were on the mainland (fig. 11) in mangrove and mangrove 

scrub habitat, using either VES or vocalization methods. A total of nine individual green treefrogs were 

captured during VES surveys, and at least one green treefrog was heard vocalizing during 19 of the 236 

samples (table 6). 

Green treefrogs were detected during March and again in May through September in the vocalization surveys and during May through August in VES surveys (table 7). This indicates that green treefrogs 

may be detectable in all seasons except winter. The period during which they were found vocalizing 

corresponds with the wetter part (May through September) of the annual rain cycle in south Florida. 

Morphometric data were collected from six green treefrogs captured during VES. The overall mean SVL 

of green treefrogs in BISC was 40.17 mm (±5.58 SD) and ranged from 30 to 47 mm (table 11).

The naïve, or minimum, site occupancy for green treefrogs was 18.92 percent overall, and the 

mean estimate of PAO was 43.67 percent (SE = 0.1519). The best model for site occupancy estimation 

included island as a site covariate and temperature as a detection covariate. Several other models had 

weight (table 13). Whether the site was on an island had the highest variable contribution (0.99), but the 

air temperature variable also had a large contribution (0.64). Relative humidity (0.22) and the presence of 

standing water (0.31) contributed very little to the model selection (table 9).

Green treefrogs were the most abundant frog found in Everglades National Park (Rice and others, 

2004). They were somewhat less commonly encountered in BISC, perhaps because they appear to be 

restricted to the mainland. Unlike cricket frogs and eastern narrowmouth toads, green treefrogs appear to 

be absent from Elliott Key, possibly due to the lack of freshwater breeding sites. The green treefrog is an 

able disperser and is highly arboreal as an adult. Inadequate breeding habitat is probably the reason for 

unsuccessful colonization of these frogs on the larger islands of BISC.

Results 9
10 Herpetofaunal Inventory of Biscayne National Park

Hyla squirella 

The squirrel treefrog (Hyla squirella) was a relatively uncommon species in BISC (fig. 12), as 

they were undetected by VES or opportunistic encounters. Detection of squirrel treefrogs by vocalization 

occurred in mangrove and mangrove scrub habitats on 2 of 236 occasions (table 6) in July and August 

(table 7). Detections using VES and vocal surveys, however, were successful in amphibian monitoring 

in Everglades National Park and Big Cypress National Preserve (Rice and others, 2004, 2005), which 

suggest that squirrel treefrogs are rare in BISC.

The squirrel treefrog appears to be restricted to the mainland in BISC. There were too few encounters 

with this species to estimate site occupancy rates. Habitats found along the strip of mainland in the park 

are probably marginal for squirrel treefrogs. Future monitoring efforts may provide more information 

about the status of squirrel treefrogs in BISC.

Osteopilus septentrionalis

The Cuban treefrog (Osteopilus septentrionalis) is an exotic hylid species possibly present in BISC 

since the 1950s (Meshaka and others, 2000). This was the most commonly documented amphibian species 

during VES. Cuban treefrogs were detected by VES in mangrove and mangrove scrub habitats, and were 

also encountered opportunistically in disturbed areas (fig. 13), a distribution consistent with known habitat 

preferences for this species (Meshaka, 2001). Cuban treefrogs were also detected during vocalization 

surveys in mangrove and mangrove scrub habitats. Individual Cuban treefrogs (49) were captured during 

VES and at least one vocalization was heard during 21 of the 236 sampling occasions (table 6). The 

overall mean SVL of Cuban treefrogs captured during this study was 57.45 mm (±15.88 SD) (table 11). 

Cuban treefrogs were detected by VES every month of the sampling year except July and December, 

indicating that they are active throughout the year and probably detectable using visual techniques. Cuban 

treefrogs were detected by vocal survey during February and during April through October (table 7).

The naïve, or minimum, site occupancy for the species was 32.43 percent overall, and the mean 

estimate of PAO was 48.61 percent (SE = 0.1157). The best model for site occupancy estimation had no 

site covariate and only relative humidity as a sampling covariate, but several other models had weight 

(table 14). Relative humidity had the highest variable contribution to model selection (0.46), and air 

temperature (0.38), island (0.31), and standing water (0.21) all had moderate contribution values (table 9). 

Occupancy rates of Cuban treefrogs were estimated as 34.7 percent (SE = 0.2156) at island sites and 56.9 

percent (SE = 0.1930) at mainland sites.

Cuban treefrogs are firmly established in BISC and were found on all of the major islands (Elliott 

Key, Boca Chita, Sands Key) as well as the mainland. They were also the most commonly encountered 

frog species during surveys. This highly invasive species (Meshaka, 2001) is a potential threat to other 

small vertebrates in the park. 

Rana grylio 

The pig frog (Rana grylio) can be found in the canals that form the boundary of BISC (fig. 14). 

This species was detected in canals during vocalization surveys, although the frogs were never actually 

in the plots. Pig frogs were heard in the vicinity of mangrove and mangrove scrub on 12 of 236 sampling 

occasions (table 6). These occurred in March through August (table 7). No pig frogs were observed 

during VES, although they were spotted in canals during opportunistic encounters on several occasions. 

During the study, no pig frogs were captured for measurement.
The pig frog is a highly aquatic species that rarely leaves permanent water (Ashton and Ashton, 

1988). Therefore, it is unlikely that this species will expand its distribution in BISC. It may be restricted 

to canals that delineate the boundary along the western edge of the park. No site occupancy estimates 

were produced for this species because it was never detected outside of the canals along the park 

boundary.

Rana sphenocephala 

The southern leopard frog (Rana sphenocephala) was encountered using VES techniques in 

mangrove habitat on 4 of 236 occasions throughout this study; three of these encounters occurred on 

one sampling occasion. Leopard frogs were heard in mangrove and mangrove scrub habitats during 5 of 

236 vocalization surveys (table 6). All detections by vocalization occurred in January and February 2003 

(table 7). Leopard frogs were observed during VES in August and June 2003 (table 7), and were observed 

during opportunistic encounters several times in mangrove and disturbed habitats, especially the levees 

near canals (fig. 15). Only one leopard frog was measured (table 11).

The naïve or minimum site occupancy for the species was 13.51 percent overall, and the estimate 

of PAO was 48.57 percent (SE = 0.0026). The best model for site occupancy estimation included island as 

a site covariate and air temperature as a sampling covariate (table 15). 

These results suggest that leopard frogs are relatively uncommon in BISC, and they appear to be 

absent from the islands. Visual methods seem to be the most reliable method of detecting leopard frogs,

especially in summer months. Vocal surveys are better in the winter, when leopard frogs tend to breed 

(Ashton and Ashton, 1988). A selective search of canal habitat may yield the best results in documenting 

this species. 

Reptiles

Although the primary focus of this study was to sample amphibian species within BISC, many of 

the methods used were also appropriate for sampling reptiles. Therefore, data on reptile species encountered during this study were collected and summarized. The BISC website (appendix II) listed 25 species 

of non-marine reptiles present in BISC. During this study, 14 of those species were encountered through 

various methods (table 16). Maps of the locations of occurrences by species are shown alphabetically 

within classes: crocodilians (figs. 16, 17); lizards (figs. 18-23); and snakes (figs. 24-29).

During this study four reptile species were found that are not native to south Florida. The brown 

anole (Anolis sagrei) was the most abundant exotic reptile found in BISC, with 246 individuals being 

observed during VES alone. Brown anoles were primarily found near disturbed areas (fig. 19). Another 

exotic, the tropical house gecko (Hemidactlyus mabouia) was also found near disturbed areas (fig. 22). 

During VES, the majority of these 26 individuals were found on buildings. The Indo-Pacific gecko 

(Hemidactylus garnotti) was found in hammock and prairie habitats on two occasions during VES 

(fig. 21). A single deceased Brahminy blindsnake (Ramphotyphlops braminus) was opportunistically 

encountered in a disturbed area on one occasion (fig. 29).

Reptiles 11
12 Herpetofaunal Inventory of Biscayne National Park

In addition to exotics, two reptile species of concern were encountered during this study. The 

American alligator, (Alligator mississippiensis), is listed as a “species of special concern” by the State 

of Florida, and as “threatened due to similarity of appearance” by the U.S. Fish and Wildlife Service 

(Federal Register 40:44149). Alligators are widespread throughout BISC and three individuals were 

found during opportunistic encounters (fig. 15). The American crocodile, (Crocodylus acutus), is listed 

as “endangered” by both the State of Florida and the U.S. Fish and Wildlife Service (Federal Register 

40:44149). Crocodiles were encountered on one occasion during VES surveys (fig. 17).

Conclusions

This study represents the first thorough inventory of amphibian species in Biscayne National Park 

(BISC), and provides a clear idea of the geographical distribution of each species throughout the park. 

The greatest value of this work is as a baseline comparison for future monitoring efforts. This inventory of 

BISC is scientifically important and was designed to alert scientists of amphibian species decline. 

The data collected during these surveys documents the distribution of amphibian species among 

habitats and across the park in 2002-2003. The proportion of area occupied (PAO) technique employed 

in this study provides a robust estimate of the true number of sites occupied by individual species, given 

that not all species are absolutely detectable. Future surveys conducted using similar methods will be 

directly comparable, because the issue of changing detectability of individuals across time and observers 

is explicitly addressed in the analysis. 

Succeeding surveys should be conducted every a 5-10 years. The surveys should use both VES and 

vocalization techniques in the field, as neither method alone was sufficient for all species. Sites should be 

selected randomly throughout BISC. Sampling could be conducted just during the warmer, wetter months 

for maximum efficiency, as very little information was obtained by including the data collected during the 

winter months. Because PAO could not be estimated for some of the rarer species, sampling efforts may 

need to be increased if monitoring of all species is desired. Estimates of proportion of sites occupied with 

confidence intervals from future monitoring can be directly compared to the estimates from this study. For 

example, an increase in PAO of 0.2 would be interpreted as a 20 percent increase in the number of sites 

occupied. Although these methods do not allow an estimate of the absolute abundance of amphibians, 

they do provide a convenient surrogate: the abundance of sites occupied by each species. This number is 

more easily obtained and comparable across time and among different sampling techniques.

Another goal of this project was to determine if there was evidence of threats to any of the 

native species of amphibians found in BISC. No amphibians captured during this study appeared to be 

threatened by disease, other health-related problems, or showed extremely low PAO when compared to 

populations in nearby Everglades National Park. The PAO for three native species found in mangrove 

habitat, however, had low captures, but this was comparable to the PAO in Everglades National Park. 

This is encouraging given the apparent declines of many amphibian species in protected areas worldwide. 

Even so, because no previous complete surveys exist, it is uncertain whether other species were formerly 

present or if the species currently present might have been formerly more abundant. Future surveys should 

provide better data of the long-term trends of distribution and abundance of the native amphibians.

The main threat to native amphibian species in BISC appears to be the presence of invasive exotic 

species. Of the nine anuran species documented in BISC, three have been introduced. These exotics are 

the Cuban treefrog (Osteopilus septentrionalis), the marine toad, cane toad or giant toad (Bufo marinus), 

and the greenhouse frog (Eleutherodactylus planirostris). All three of these introduced species were 

discovered on the islands of BISC and represent 60 percent of the amphibian species on these islands. 
Further, the estimated mean PAO of the invasive species (ranging 48.61 to 77.90) were higher than any of 

the native species (ranging 35.0 to 48.57) and were encountered almost three times as often in our study. 

The two native anurans found on the islands, the narrowmouth toad (Gastrophryne carolinensis) and the 

cricket frog (Acris gryllus), were only observed on Elliott Key. All three of the introduced species were 

relatively common and were found on numerous occasions on many islands. 

The Cuban treefrog and the giant toad were found in a variety of habitats. The Cuban treefrog has 

reached very high densities at some sites in Everglades National Park, especially near Flamingo and in 

Long Pine Key. The diet of the Cuban tree frog includes a variety of vertebrate prey. The impact to the 

native treefrog assemblage is under investigation, but it appears that the combination of direct and indirect 

competition and predation allows Cuban treefrogs to increase to the detriment of native species. The 

marine toad is another introduced species that may have a negative impact on native fauna of BISC. This 

species is also an aggressive predator, and although it is relatively rare in the natural areas of south Florida 

now, it may be increasing in abundance and expanding its range.

Acknowledgments

The authors would like to thank the technicians that assisted with the field work in this 

project: University of Florida staff Amber Dove, Andy Maskell, and Phil George. The staff 

at Biscayne National Park provided valuable logistical help. Matt Patterson, National Park 

Service Inventory and Monitoring Program is appreciated for providing funding and for helping 

to initiate this project. Biscayne National Park loaned a vehicle and allowed the use of their boat 

launch. Administrative services were managed by the support staff at the University of Florida, 

Ft. Lauderdale Research and Education Center, especially Sarah Kern, Veronica Woodward, 

Jocie Graham, Alicia Weinstein, and Valerie Chartier. Valuable comments were provided for this 

manuscript by Amanda Rice (University of Florida) and Mike Deacon (U.S. Geological Survey).

Acknowledgments 13
14 Herpetofaunal Inventory of Biscayne National Park

References 

Alford, R.A., and Richards, S.J., 1999, Global amphibian declines: A problem in applied ecology: Annual 

Review of Ecology and Systematics, v. 30, p. 133-165.

Ashton, R.E., and Ashton, P.S., 1988, Handbook of reptiles and amphibians of Florida, Part three: The 

amphibians: Miami, Windward Publishing.

Burnham, K.P., and Anderson D.R., 1998, Model selection and multi-model inference: A practical 

information-theoretic approach: New York, Springer-Verlag, 353 p.

Carey, C., and Bryant C.J., 1995, Possible interrelations among environmental toxicants, amphibian 

development, and decline of amphibian populations: Environmental Health Perspectives, v. 103, no. 4, 

p. 13-17.

Conant, R., and Collins J.T., 1991, A field guide to reptiles and amphibians: Eastern and central North 

America (3d ed.): Boston, Houghton Mifflin Company, 450 p.

Dodd, C.K., Jr., and Cade, B.S., 1998, Movement patterns and the conservation of amphibians breeding in 

small, temporary wetlands: Conservation Biology, v. 12, no. 2, p. 331-339.

Duellman, W.E., and Schwartz A., 1958, Amphibians and reptiles of southern Florida: Gainesville, Florida 

State Museum [Florida Museum of Natural History], v. 3, no. 5, p. 181-324. 

Heyer, W.R., Donnelly, M.A., McDiarmid, R.W., Hayek, L.C., and Foster, M.S., 1994, Measuring and 

monitoring biological diversity: Standard methods for amphibians: Washington, D.C., Smithsonian 

Institution Press, 364 p.

Hooge, P.N., and Eichenlaub, B., 1997, Animal movement extension to ArcView: Alaska Science 

Center—Biological Science Office, U.S Geological Survey, Anchorage, AK, USA.

MacKenzie, D.I., 2002, Modeling handout: U.S. Geological Survey Patuxent Wildlife Research Center, 6 p.

MacKenzie, D.I., Nichols, J.D., Lachman, G.B., Droege, S., Royle, J.A., and Langtimm, C.A., 2002, 

Estimating site occupancy rates when detection probabilities are less than one: Ecology v. 83, no. 8, 

p. 2248-2256.

Madden, M., Jones, D., and Vilchek, L., 1999, Photointerpretation key for the Everglades vegetation 

classification system: Photogrammetric Engineering & Remote Sensing, v. 65, no. 22, p. 171-177.

Maskell, A.J., Waddle, J.H., and Rice, K.G., 2003, Osteopilus septentrionalis: Diet: Herpetological 

Review, v. 34, p. 137.

Meshaka, W.E., 2001, The Cuban treefrog in Florida: Gainesville, University of Florida Press, 191 p.

Meshaka W.E., Butterfield, B.P., and Hauge, J.B., 2004, The exotic amphibians and reptiles of Florida: 

Malabar, Fla., Krieger Publishing Co., 155 p.

Meshaka, W.E., Loftus, W.F., and Steiner, T., 2000, The herpetofauna of Everglades National Park: Florida 

Scientist, v. 63, no. 2, p. 84-103.

Rice, K.G., Waddle, J.H., Crockett, M.E., Jeffrey, B.M., and Percival, H.F., 2004, Herpetofaunal 

Inventories of the National Parks of South Florida and the Caribbean: Volume 1. Everglades National 

Park: U.S. Geological Survey Open-File Report 2004-1065, 144 p.

Rice, K.G., Waddle, J.H., Crockett, M.E., Jeffrey, B.M., and Percival, H.F., 2005, Herpetofaunal 

inventories of the national parks of south Florida and the Caribbean: Volume III. Big Cypress National 

Preserve: U.S. Geological Survey Open-File Report 2005-1300, 156 p.

Waddle, J.H., Rice, K.G., and Percival, H.F., 2003, Using personal digital assistants to collect wildlife 

field data: Gainesville, University of Florida, Wildlife Society Bulletin, v. 31, no. 1, p. 306-308.
 

 

Figures 1–29

 
16 Herpetofaunal Inventory of Biscayne National Park
Figure 1. Southern Florida, showing Biscayne National Park.

Biscayne

National

Park

0 100 KILOMETERS

0 10 20 30 40 50

20 40 60 80

60 MILES

Homestead

Miami

Miami-Dade County

Key

Largo

Figures 1–29 17
18 Herpetofaunal Inventory of Biscayne National Park

Figure 2. Biscayne National Park.

Florida

Atlantic

Ocean

Biscayne

National

Park

0 10 KILOMETERS

0 1 2 3 4 5

2 4 6 8

6 MILES

Elliott Key

Sands Key

Old Rhodes Key

Key Biscayne

Boca Chita

Key
Figure 3. Four major habitats within Biscayne National Park.

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

0

MILES

KILOMETERS

1 3

0 1 2 3

2

0 6

0 1 2 3

2 4

4

1 3 5

KILOMETERS

MILES

0 1 2 MILES

0 1 2 KILOMETERS

Elliott Key

Sands Key

Old Rhodes

Key

Boca Chita

Key

Figures 1–29 19
20 Herpetofaunal Inventory of Biscayne National Park

Figure 4. Sampling locations in Biscayne National Park where visual encounter surveys and vocalization 

surveys were conducted during this study at least twice at 37 sites.

0 1 2 MILES

0 1 2 KILOMETERS

MILES

KILOMETERS

0 1 2 3

0 1 2 3

MILES

KILOMETERS

0 1 2 3 4

0 1 2 3 4

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Sampling Points

Location

Hammock Vegetation

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key
Figure 5. Sampling locations in Biscayne National Park where visual encounter surveys and vocalization 

surveys were conducted during this study on a monthly basis at 16 sites.

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Sampling Points

Location

EXPLANATION

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

1 2 3 4

0

KILOMETERS

1 2 3 4

0

MILES

KILOMETERS

1 2 3

0 1 2 3

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Figures 1–29 21
22 Herpetofaunal Inventory of Biscayne National Park

Figure 6. Locations in Biscayne National Park where Acris gryllus was observed.

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Sampled Locations

Acris gryllus

VES/Vocalization Observation

Not Observed

EXPLANATION

Opportunistic

0 1 2 MILES

0 1 2 KILOMETERS

MILES

0

KILOMETERS

123

0 1 2 3

MILES

KILOMETERS

0 1 2

0 1 2 3 4

3 4

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key
Figure 7. Locations in Biscayne National Park where Bufo marinus was observed.

0 1 2 MILES

0 1 2 KILOMETERS

MILES

KILOMETERS

0 1 2

0 1 2

3

3

0

MILES

0

KILOMETERS

1

1

2

2

3

3

4

4

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Sampled Locations

Bufo marinus

VES/Vocalization Observation

Opprotunistic

Not Observed

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Figures 1–29 23
24 Herpetofaunal Inventory of Biscayne National Park

Figure 8. Locations in Biscayne National Park where Bufo terrestris was observed.

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Sampled Locations

Bufo terrestris

VES/Vocalization Observation

EXPLANATION

Opprotunistic

Not Observed

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

1

123

2 3

0

MILES

0

KILOMETERS

123 4

1234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key
Figure 9. Locations in Biscayne National Park where Eleutherodactylus planirostris was observed.

( 0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Sampled Locations

Eleutherodactylus planirostris

VES/Vocalization Observation

Opprotunistic

Not Observed

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Figures 1–29 25
26 Herpetofaunal Inventory of Biscayne National Park

Figure 10. Locations in Biscayne National Park where Gastrophryne carolinensis was observed.

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

0 1 2 MILES

0 1 2 KILOMETERS

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Sampled Locations

Gastrophryne carolinensis

VES/Vocalization Observation

Opprotunistic

Not Observed

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key
Figure 11. Locations in Biscayne National Park where Hyla cinerea was observed.

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Sampled Locations

EXPLANATION

Hyla cinerea

VES/Vocalization Observation

Opprotunistic

Not Observed

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Figures 1–29 27
28 Herpetofaunal Inventory of Biscayne National Park

Figure 12. Locations in Biscayne National Park where Hyla squirella was observed.

Kilometers

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Sampled Locations

Hyla squirella

VES/Vocalization Observation

Opportunistic

Not Observed

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key
Figure 13. Locations in Biscayne National Park where Osteopilus septentrionalis was observed.

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Sampled Locations

Osteopilus septentrionalis

VES/Vocalization Observation

Opportunistic

Not Observed

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Figures 1–29 29
30 Herpetofaunal Inventory of Biscayne National Park

Figure 14. Locations in Biscayne National Park where Rana grylio was observed.

(

(

(

(

(

(

(

(

( (

(

(

(

(

(

(

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Sampled Locations

Rana grylio

VES/Vocalization Observation

Opprotunistic

Not Observed

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key
Figure 15. Locations in Biscayne National Park where Rana sphenocephala was observed.

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Sampled Locations

Rana sphenocephala

VES/Vocalization Observation

Opportunistic

Not Observed

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Figures 1–29 31
32 Herpetofaunal Inventory of Biscayne National Park

Figure 16. Locations in Biscayne National Park where Alligator mississippiensis was observed.

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Alligator mississippiensis

Observed

Opportunistic Encounter

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key
Figure 17. Locations in Biscayne National Park where Crocodylus acutus was observed.

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Crocodylus acutus

Observed

Opportunistic Encounter

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Figures 1–29 33
34 Herpetofaunal Inventory of Biscayne National Park

Figure 18. Locations in Biscayne National Park where Anolis carolinensis was observed.

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Anolis carolinensis

VES/Vocalization Observation

Opportunistic

Not Observed

Sampled Locations

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key
Figure 19. Locations in Biscayne National Park where Anolis sagrei was observed.

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Sampled Locations

Anolis sagrei

VES/Vocalization Observation

Not Observed

Opportunistic

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Figures 1–29 35
36 Herpetofaunal Inventory of Biscayne National Park

Figure 20. Locations in Biscayne National Park where Eumeces inexpectatus was observed.

Eumeces inexpectatus

Observed

Opportunistic Encounter

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key
Figure 21. Locations in Biscayne National Park where Hemidactylus garnotti was observed.

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Observed

Opportunistic Encounter

Hemidactylus garnotii

Figures 1–29 37
38 Herpetofaunal Inventory of Biscayne National Park

Figure 22. Locations in Biscayne National Park where Hemidactlyus mabouia was observed.

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Observed

Opportunistic Encounter

Hemidactylus mabouia
Figure 23. Locations in Biscayne National Park where Sphaerodactylus notatus was observed.

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Observed

Opportunistic Encounter

Sphaerodactylus notatus

Figures 1–29 39
40 Herpetofaunal Inventory of Biscayne National Park

Figure 24. Locations in Biscayne National Park where Diadophis punctatus was observed.

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Observed

Opportunistic Encounter

Diadophis punctatus
Figure 25. Locations in Biscayne National Park where Elaphe guttata was observed.

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Observed

Opportunistic Encounter

Elaphe guttata

Figures 1–29 41
42 Herpetofaunal Inventory of Biscayne National Park

Figure 26. Locations in Biscayne National Park where Elaphe obsoleta was observed.

Observed

Opportunistic Encounter

Elaphe obsoleta

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key
Figure 27. Locations in Biscayne National Park where Nerodia clarkii was observed.

Observed

Opportunistic Encounter

Nerodia clarkii

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Figures 1–29 43
44 Herpetofaunal Inventory of Biscayne National Park

Figure 28. Locations in Biscayne National Park where Nerodia fasciata was observed.

Observed

Opportunistic Encounter

Nerodia fasciata

EXPLANATION

Vegetation Type

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key
Figure 29. Locations in Biscayne National Park where Ramphotyphlops braminus was observed.

EXPLANATION

0 1 2 MILES

0 1 2 KILOMETERS

0

MILES

0

KILOMETERS

123

123

0

MILES

0

KILOMETERS

1

1234

234

Boca Chita

Key

Elliott Key

Sands Key

Old Rhodes

Key

Ramphotyphlops raminus

Observed

Vegetation Type Opportunistic Encounter

Disturbed

Mangrove

Mangrove Scrub

Prairie

Biscayne National Park

Figures 1–29 45
46 Herpetofaunal Inventory of Biscayne National Park
 

Tables 1–16 

 
48 Herpetofaunal Inventory of Biscayne National Park
Table 1. Vegetation classification of Key Biscayne National Park.

CODE Description Vegetation 

classification

BCH Beach

C Canal

E Exotic Disturbed

EA Shoebutton Ardisia (Ardisia elliptica) Disturbed

EC Australian Pine (Casuarina spp.) Disturbed

EJ Java Plum (Syzygium cuminii) Disturbed

EL Tropical Soda Apple (Solanum viarum) Disturbed

EM Cajeput (Melaleuca quinquenervia) Disturbed

EO Lather Leaf (Colubrina asiatica) Disturbed

ES Brazilian Pepper (Schinus terebinthifolius) Disturbed

F Forest Hammock

FB Buttonwood Forest (Conocarpus erectus) Hammock

FC Cabbage Palm Forest (Sabal palmetto) Hammock

FM Mangrove Forest Mangrove

FMa Black (Avicennia germinans) Mangrove

FMl White (Laguncularia racemosa) Mangrove

FMr Red (Rhizophora mangle) Mangrove

FMx Mixed Mangroves Mangrove

FO Oak-Sabal Forest Hammock

FP Paurotis Palm Forest (Acoelorrhaphe wrightii) Hammock

FS Swamp Forest Hammock

FSCpi Cypress-Pines

FSa Mixed Hardwood, Cypress, Pine Hammock

FSb Bayhead Hammock

FSbc Cocoplum Hammock

FSc Cypress Strand/Head

FSd Cypress Dome

FSh Mixed Hardwood Hammock

FSx Mixed Hardwood, Cypress Hammock

FT Subtropical Hardwood Forest Hammock

HI Human Influence Disturbed

HIp Pumping Station Disturbed

MUD Mud

ORV Off Road Vehicle Trails Disturbed

P Prairie/Marsh Prairie

PC Cat-tail Prairie

PE Non-graminoid Emergent Marsh Prairie

PEb Broadleaf Emergents Prairie

PG Graminoid Prairie Prairie

PGa Maidencane Prairie

PGc Saw Grass (Cladium jamaicense) Prairie

PGct Tall Saw Grass Prairie

PGe Spike-rush (Eleocharis cellulosa) Prairie

PGj Black-rush (Juncus roemerianus) Prairie

PGm Muhly Prairie

Tables 1–16 49
50 Herpetofaunal Inventory of Biscayne National Park

CODE Description Vegetation 

classification

PGp Common Reed (Phragmites spp.) Prairie

PGs Cord Grass (Spartina spp.) Prairie

PGw Maidencane/Spike-rush Prairie

PGx Mixed Graminoids Prairie

PH Halophytic Herbaceous Prairie Prairie

PHg Graminoid Prairie

PHs Succulent Prairie

PND Pond

PPI Prairie with Scattered Pine Prairie

PR Pinnacle Rock

RD Road Disturbed

S Scrub Hammock

SA Spoil Area Disturbed

SB Shrubland Hammock

SBb Groundsel Bush (Baccharis spp.) Hammock

SBc Buttonbush (Cephalanthus occidentalis) Hammock

SBf Pop Ash (Fraxinus caroliniana) Hammock

SBl Primrose (Ludwigia spp.) Hammock

SBm Wax Myrtle (Myrica cerifera) Hammock

SBs Willow (Salix caroliniana) Hammock

SBy Cocoplum (Chrysobalanus icaco) Hammock

SC Buttonwood Scrub (Conocarpus erectus) Mangrove Scrub

SH Hardwood Scrub Mangrove Scrub

SM Mangrove Scrub Mangrove Scrub

SMa Black (Avicennia germinans) Mangrove Scrub

SMl White (Laguncularia racemosa) Mangrove Scrub

SMr Red (Rhizophora mangle) Mangrove Scrub

SMx Mixed Mangroves Mangrove Scrub

SP Saw Palmetto Scrub Hammock

SS Bay-Hardwood Scrub Hammock

SV Savanna Prairie

SVC Cypress Savanna

SVCd Dwarf Cypress

SVCpi Cypress with Pine

SVPI Pine Savanna

SVPIc Slash Pine with Cypress

SVPIh Slash Pine with Hardwood

SVx Slash Pine with Palm

SVPM Palm Savanna Hammock

W Water

Table 1. (Continued) Vegetation classification of Key Biscayne National Park.
Table 2. The 14 models evaluated for most amphibian species to determine the estimate of proportion 

of area occupied.

(Psi) and detection probability (p).

Model description Site 

covariates Sampling occasion covariates

Psi(.); p(.) Constant Constant

Psi(.); p(humid) Constant Relative humidity

Psi(.); p(temp) Constant Air temperature

Psi(.); p(temp, humid) Constant Air temperature and relative humidity

Psi(.); p(temp, humid, water) Constant Air temperature, relative humidity, and presence of water

Psi(.); p(temp, water) Constant Air temperature and presence of water

Psi(.); p(water) Constant Presence of water

Psi(island); p(.) Island Constant

Psi(island); p(humid) Island Relative humidity

Psi(island); p(temp) Island Air temperature

Psi(island); p(temp, humid) Island Air temperature and relative humidity

Psi(island); p(temp, humid, water) Island Air temperature, relative humidity, and presence of water

Psi(island); p(temp, water) Island Air temperature and presence of water

Psi(island); p(water) Island Presence of water

Tables 1–16 51
52 Herpetofaunal Inventory of Biscayne National Park

Table 3. Location, number of visits, and habitat type of sampled sites. 

[Coordinates are in Universal Transverse Mercator system Zone 17 North, based on the 

World Geodetic System 1984 datum]

Plot

number

Sampled 

monthly Habitat type Island UTMeasting

UTM 

northing

402 x Hammock Boca Chita 582892 2822974

401 x Hammock Sands Key 582421 2820194

306 x Mangrove Elliott Key 581293 2815396

301 x Mangrove Mainland 567087 2822677

302 x Mangrove Mainland 566112 2819702

303 x Mangrove Boca Chita 582877 2823091

305 x Mangrove Elliott Key 579251 2810461

307 x Mangrove Sands Key 582543 2820924

304 x Mangrove Elliott Key 580487 2814119

202 x Prairie Elliott Key 579871 2812313

201 x Prairie Elliott Key 578855 2809952

105 x Mangrove scrub Elliott Key 580896 2814731

104 x Mangrove scrub Elliott Key 579809 2811817

103 x Mangrove scrub Elliott Key 579614 2811208

102 x Mangrove scrub Mainland 565728 2816804

101 x Mangrove scrub Mainland 565691 2818731

256 Disturbed Adams Key 576858 2809369

111 Hammock Old Rhodes Key 577110 2807865

145 Mangrove Adams Key 577268 2809440

166 Mangrove Mainland 569272 2827346

182 Mangrove Mainland 567496 2825117

195 Mangrove Mainland 567633 2811351

214 Mangrove Adams Key 576988 2809158

252 Mangrove Old Rhodes Key 576402 2808943

499 Mangrove Elliott Key 581246 2815877

300 Mangrove Mainland 565925 2816925

308 Mangrove Elliott Key 579801 2812668

385 Mangrove Mainland 566222 2817745

399 Mangrove Mainland 566113 2819691

234 Mangrove Mainland 567837 2824690

23 Mangrove scrub Mainland 566329 2816456

143 Mangrove scrub Mainland 566201 2815861

123 Mangrove scrub Mainland 566232 2814697

310 Mangrove scrub Mainland 565814 2816878

485 Mangrove scrub Mainland 565697 2817584

497 Mangrove scrub Mainland 565728 2817068

65 Mangrove scrub Mainland 566725 2814761
Table 4. Amphibian detection in vegetation classification. 

Species Introduced Disturbed Mangrove Mangrove 

scrub Prairie Hammock

Acris gryllus x x

Bufo marinus x x x x

Bufo quercicus

Bufo terrestris x

Eleutherodactylus planirostris x x x x

Gastrophryne carolinensis x

Hyla cinerea x x

Hyla squirella x x

Osteopilus septentroinalis x x x x

Rana grylio x x

Rana sphenocephala x x

Tables 1–16 53

Table 5. Amphibian average proportion of area 

occupied (PAO) estimate comparisons. 

[SE, standard error of the estimate; –, no data]

Species PAO 

estimate SE

Acris gryllus 35.0 0.2096

Bufo marinus 77.9 0.1499

Bufo quercicus – –

Bufo terrestris – –

Eleutherodactylus planirostris 54.4 0.1077

Gastrophryne carolinensis – –

Hyla cinerea 43.7 0.1519

Hyla squirella – –

Osteopilus septentroinalis 48.6 0.1157

Rana grylio – –

Rana sphenocephala 48.6 0.0026
54 Herpetofaunal Inventory of Biscayne National Park

Table 6. Number of individuals captured and number of site visits when at 

least one of each species was heard vocalizing out of 236 possible samples. 

Species Individual 

captures

Visits with 

vocalizations 

detected

Total

Acris gryllus 0 6 6

Bufo marinus 0 31 31

Eleutherodactylus planirostris 38 26 64

Hyla cinerea 9 19 28

Hyla squirella 0 2 2

Osteopilus septentroinalis 49 21 70

Rana grylio 0 12 12

Rana sphenocephala 4 5 9

 Total 100 122 222
Table 7. Months in 2003 when individuals were detected by visual encounter 

survey (VES) methods and by vocalization.

Survey method Jan. Feb. Mar. April May June July Aug. Sept. Oct. Nov. Dec.

Acris gryllus 

VES

Vocalization x x x x x

Bufo marinus

VES

Vocalization x x x x x x x x x

Eleutherodactylus planirostris

VES x x x x x x x x

Vocalization x x x x x

Hyla cinerea

VES x x x x

Vocalization x x x x x x

Hyla squirella

VES

Vocalization x x

Osteopilus septentroinalis

VES x x x x x x x x x x

Vocalization x x x x x x x x

Rana grylio

VES

Vocalization x x x x x x

Rana sphenocephala

VES x x

Vocalization x x

Tables 1–16 55
56 Herpetofaunal Inventory of Biscayne National Park

Table 8. Results of proportion of area occupied analysis for Acris gryllus.

[ψ (Psi) = The estimate of the proportion of sites occupied, SE, standard error of the estimate, k, number of parameters, ∆AICc , 

the difference from the lowest value of the Akaike’s Information Criterion for small sample sizes]

Model ψ SE -2log likelihood k ∆AICc Model weight

Psi(island); p(.) 0.3498 0.2096 49.3498 3 0.0000 0.2426

Psi(.); p(.) 0.2639 0.1545 52.4231 2 0.6990 0.1710

Psi(.); p(water) 0.6502 0.5717 50.8756 3 1.5258 0.1131

Psi(island); p(water) 0.6502 0.5717 50.8756 3 1.5258 0.1131

Psi(island); p(temp) 0.3483 0.2085 49.2302 4 2.4031 0.0729

Psi(island); p(humid) 0.3468 0.2093 49.2633 4 2.4362 0.0717

Psi(.); p(temp) 0.2630 0.1543 52.3225 3 2.9727 0.0549

Psi(.); p(humid) 0.2596 0.1521 52.3484 3 2.9986 0.0542

Psi(.); p(temp, water) 0.6516 0.5756 50.8648 4 4.0377 0.0322

Psi(island); p(temp, water) 0.4645 0.3624 48.8539 5 4.7123 0.0230

Psi(island); p(temp, humid) 0.3451 0.2081 49.1687 5 5.0271 0.0196

Psi(.); p(temp, humid) 0.2588 0.1522 52.2664 4 5.4393 0.0160

Psi(.); p(temp, humid, water) 0.6711 0.5995 50.6239 5 6.4823 0.0095

Psi(island); p(temp, humid, water) 0.4995 0.4077 48.6233 6 7.3462 0.0062

Table 9. Contribution of four different variables to the occupancy model selection of six amphibian species. 

[The values are the sum of Akaike weights of all models containing the variables]

Variable Acris gryllus Bufo marinus Eleutherodactylus 

planirostris Hyla cinerea Osteopilus septentroinalis 

Rana 

sphenocephala 

Island 0.549 0.182 0.694 0.999 0.313 0.998

Air temperature 0.234 0.407 0.997 0.639 0.384 0.991

Relative humidity 0.177 0.496 0.489 0.215 0.455 0.206

Presence of water 0.297 0.246 0.208 0.306 0.211 0.213
Table 10. Results of proportion of area occupied analysis for Bufo marinus.

[ψ = The estimate of the proportion of sites occupied, SE, standard error of the estimate, k, number of parameters, ∆AICc, the 

difference from the lowest value of the Akaike’s Information Criterion for small sample sizes]

Model ψ SE -2log likelihood k ∆AICc Model 

weight

Psi(.); p(humid) 0.7527 0.1423 176.9638 3 0.0000 0.2930

Psi(.); p(.) 0.7748 0.1453 180.5923 2 1.2542 0.1565

Psi(.); p(temp, humid) 0.7553 0.1441 176.2032 4 1.7621 0.1214

Psi(.); p(temp) 0.7783 0.1481 178.9633 3 1.9995 0.1078

Psi(island); p(water) 0.8603 0.0807 179.5232 3 2.5594 0.0815

Psi(.); p(water) 0.7637 0.1415 180.0704 3 3.1066 0.0620

Psi(.); p(temp, water) 0.7637 0.1432 178.2828 4 3.8417 0.0429

Psi(island); p(temp) 0.8692 0.2342 178.5011 4 4.0600 0.0385

Psi(island); p(temp, humid) 0.8280 0.2153 175.9078 5 4.1522 0.0368

Psi(.); p(temp, humid, water) 0.7531 0.1421 176.0409 5 4.2853 0.0344

Psi(island); p(temp, water) 0.8585 0.0817 177.6792 5 5.9236 0.0152

Psi(island); p(temp, humid, water) 0.8411 0.2181 175.6452 6 6.7541 0.0100

Psi(island); p(.) 1.0000 0.0000 183.0214 3 99.0000 0.0000

Psi(island); p(humid) 1.0000 0.0000 180.1045 4 99.0000 0.0000

Table 11. Snout-to-vent length of amphibian species captured in Biscayne National Park.

[SD, standard deviation]

Species Number of 

individuals

Mean snout-vent length 

(± SD)

Range of snout-vent 

length (millimeters)

Eleutherodactylus planirostris 6 19.33 (± 4.32) 11-23

Hyla cinerea 6 40.17 (± 5.85) 30-47

Osteopilus septentroinalis 20 57.45 (± 15.88) 34-95

Rana sphenocephala 1 80 (± 0) 80-80

Tables 1–16 57
58 Herpetofaunal Inventory of Biscayne National Park

Table 12. Results of proportion of area occupied analysis for Eleutherodactylus planirostris.

[ψ = The estimate of the proportion of sites occupied, SE, standard error of the estimate, k, number of parameters, ∆AICc, 

the difference from the lowest value of the Akaike’s Information Criterion for small sample sizes]

Model ψ SE -2log likelihood k ∆AICc Model 

weight

Psi(island); p(temp) 0.5300 0.1007 174.8847 4 0.0000 0.2829

Psi(island); p(temp, humid) 0.5259 0.1006 172.2965 5 0.0973 0.2695

Psi(.); p(temp, humid) 0.5775 0.1151 176.5961 4 1.7114 0.1202

Psi(.); p(temp) 0.5812 0.1149 179.1717 3 1.7643 0.1171

Psi(island); p(temp, water) 0.5300 0.1009 174.8847 5 2.6855 0.0739

Psi(island); p(temp, humid, water) 0.5266 0.1011 172.2755 6 2.9408 0.0650

Psi(.); p(temp, water) 0.5837 0.1156 179.1141 4 4.2294 0.0341

Psi(.); p(temp, humid, water) 0.5811 0.1158 176.4549 5 4.2557 0.0337

Psi(island); p(water) 0.5399 0.1001 188.3529 3 10.9455 0.0012

Psi(island); p(.) 0.5405 0.1003 188.3717 3 10.9643 0.0012

Psi(island); p(humid) 0.5392 0.0999 187.5093 4 12.6246 0.0005

Psi(.); p(.) 0.5967 0.1180 193.1851 2 13.4033 0.0003

Psi(.); p(humid) 0.5939 0.1175 192.3706 3 14.9632 0.0002

Psi(.); p(water) 0.5979 0.1185 193.1708 3 15.7634 0.0001

Table 13. Results of proportion of area occupied analysis for Hyla cinerea.

[ψ = The estimate of the proportion of sites occupied, SE, standard error of the estimate, k, number of parameters, ∆AICc, 

the difference from the lowest value of the Akaike’s Information Criterion for small sample sizes]

Model ψ SE -2log likelihood k ∆AICc Model 

weight

Psi(island); p(temp) 0.4409 0.1460 85.6807 4 0.0000 0.3665

Psi(island); p(water) 0.4399 0.1618 89.8806 3 1.6772 0.1585

Psi(island); p(.) 0.4480 0.1599 89.9193 3 1.7159 0.1554

Psi(island); p(temp, humid) 0.4398 0.1493 85.1491 5 2.1539 0.1249

Psi(island); p(temp, water) 0.4199 0.1438 85.5037 5 2.5085 0.1046

Psi(island); p(humid) 0.4366 0.1584 89.7859 4 4.1052 0.0471

Psi(island); p(temp, humid, water) 0.3827 0.1425 84.4379 6 4.3072 0.0425

Psi(.); p(temp) 0.2702 0.0916 103.5944 3 15.3910 0.0002

Psi(.); p(.) 0.2732 0.0928 107.1238 2 16.5460 0.0001

Psi(.); p(temp, humid) 0.2693 0.0915 102.7819 4 17.1012 0.0001

Psi(.); p(temp, water) 0.2623 0.0895 103.1157 4 17.4350 0.0001

Psi(.); p(temp, humid, water) 0.2482 0.0848 100.7582 5 17.7630 0.0001

Psi(.); p(humid) 0.2726 0.0924 106.6235 3 18.4201 0.0000

Psi(.); p(water) 0.2680 0.0917 106.9251 3 18.7217 0.0000
Table 14. Results of proportion of area occupied analysis for Osteopilus septentroinalis.

[ψ = The estimate of the proportion of sites occupied, SE, standard error of the estimate, k, number of parameters, ∆AICc, 

the difference from the lowest value of the Akaike’s Information Criterion for small sample sizes]

Model ψ SE -2log likelihood k ∆AICc Model 

weight

Psi(.); p(humid) 0.4699 0.1095 193.0980 3 0.0000 0.2056

Psi(.); p(.) 0.4867 0.1125 196.0967 2 0.6244 0.1504

Psi(.); p(temp) 0.4822 0.1117 194.3231 3 1.2251 0.1114

Psi(.); p(temp, humid) 0.4685 0.1090 191.9424 4 1.3671 0.1038

Psi(island); p(humid) 0.4895 0.1184 192.6266 4 2.0513 0.0737

Psi(island); p(water) 0.5178 0.1267 195.1945 3 2.0965 0.0721

Psi(island); p(.) 0.5158 0.1261 195.4577 3 2.3597 0.0632

Psi(.); p(water) 0.4862 0.1123 195.8952 3 2.7972 0.0508

Psi(island); p(temp) 0.5123 0.1246 193.6117 4 3.0364 0.0450

Psi(.); p(temp, water) 0.4812 0.1113 193.9649 4 3.3896 0.0378

Psi(island); p(temp, humid) 0.4898 0.1178 191.3946 5 3.5048 0.0356

Psi(.); p(temp, humid, water) 0.4688 0.1091 191.9316 5 4.0418 0.0272

Psi(island); p(temp, water) 0.5145 0.1250 193.1624 5 5.2726 0.0147

Psi(island); p(temp, humid, water) 0.4916 0.1188 191.3585 6 6.3332 0.0087

Table 15. Results of proportion of area occupied analysis for Rana sphenocephala.

[ψ = The estimate of the proportion of sites occupied, SE, standard error of the estimate, k, number of parameters, ∆AICc, 

the difference from the lowest value of the Akaike’s Information Criterion for small sample sizes]

Model ψ SE -2log likelihood k ∆AICc Model 

weight

Psi(island); p(temp) 0.4865 0.0000 34.0035 4 0.0000 0.6174

Psi(island); p(temp, water) 0.4865 0.0000 33.9442 5 2.6262 0.1661

Psi(island); p(temp, humid) 0.4865 0.0000 33.9631 5 2.6451 0.1645

Psi(island); p(temp, humid, water) 0.4865 0.0000 33.9209 6 5.4674 0.0401

Psi(island); p(water) 0.4230 0.1964 45.7645 3 9.2383 0.0061

Psi(island); p(.) 0.4865 0.0000 47.4744 3 10.9482 0.0026

Psi(.); p(temp) 0.3249 0.1573 48.6121 3 12.0859 0.0015

Psi(island); p(humid) 0.4865 0.0000 47.4438 4 13.4403 0.0007

Psi(.); p(temp, humid) 0.3218 0.1559 48.5575 4 14.5540 0.0004

Psi(.); p(temp, water) 0.3185 0.1675 48.6048 4 14.6013 0.0004

Psi(.); p(temp, humid, water) 0.3210 0.1700 48.5574 5 17.2394 0.0001

Psi(.); p(.) 0.3267 0.1757 60.1540 2 21.2534 0.0000

Psi(.); p(water) 0.2429 0.1113 58.6454 3 22.1192 0.0000

Psi(.); p(humid) 0.3298 0.1830 60.1486 3 23.6224 0.0000

Tables 1–16 59
60 Herpetofaunal Inventory of Biscayne National Park

Table 16. Reptile species observed during amphibian inventory in Biscayne National Park during 2002-2003 

and method of detection.

[VES, visual encounter survey]

Family Genus Species Common name VES Opportunistic

Order Crocodylia

Alligatoridae Alligator mississipiensis American alligator x

Crocodylidae Crocodylus acutus American crocodile x

Order Squamata, suborder sauria

Gekkonidae Hemidactylus mabouia Amerafrican house gecko x x

Gekkonidae Hemidactylus garnotii Indo-Pacific gecko x x

Gekkonidae Sphaerodactylus notatus Florida reef gecko x

Polycrotidae Anolis sagrei Brown anole x x

Polycrotidae Anolis carolinensis Green anole x x

Scincidae Eumeces inexpectatus Southeastern five-lined skink x

Order Squamata, suborder serpentes

Colubridae Diadophis punctatus Southern ringneck snake x x

Colubridae Elaphe obsoleta Yellow rat snake x

Colubridae Elaphe guttata Corn snake x

Colubridae Nerodia fasciata Florida water snake x x

Colubridae Nerodia clarkii Mangrove salt marsh snake x

Typhlopidae Ramphotyphlops raminus Brahminy blind snake x
 

Appendixes I–II 

 

 
62 Herpetofaunal Inventory of Biscayne National Park
Appendix I. Best models of proportion area occupied by species.

[% CI, percent confidence interval]

Acris gryllus Best model: Psi (island), p (.)

Beta SE 95% CI lower 95% CI upper

Psi Intercept 0.4159 1.6137 0.6025 0.3865

Psi Island -2.5025 1.7532 0.0757 0.1226

p intercept -2.3085 0.6702 0.0904 0.0551

Anolis sagrei

Best model: Psi (island), p (humid, temp, water)

Beta SE 95% CI lower 95% CI upper

Psi Intercept 0.6128 0.7766 0.6486 0.177

Psi Island 24.0875 -105666 1 0

p intercept -1.2533 0.4164 0.2221 0.072

p Humid 10.9642 3.6694 1 0.0001

p Temp -0.183 0.051 0.4544 0.0127

p Water -0.7167 0.3821 0.3281 0.0842

Bufo marinus

Best model: Psi (.), p (humid)

Beta SE 95% CI lower 95% CI upper

Psi Intercept 1.1129 0.7642 0.7527 0.1423

p intercept -2.5413 0.5685 0.073 0.0385

p Humid 9.0023 4.8832 0.9999 0.0006

Hemidactylus mabouia

Best model: Psi (.), p (temp, humid)

Beta SE 95% CI lower 95% CI upper

Psi Intercept 0.8677 1.0358 0.7043 0.2157

p intercept -3.3859 0.7947 0.0327 0.0252

p Humid 10.1017 6.6417 1 0.0003

p Temp -0.1485 0.1095 0.4629 0.0272

Osteopilus septentroinalis

Best model: Psi (.), p (humid)

Beta SE 95% CI lower 95% CI upper

Psi Intercept -0.1204 0.4396 0.4699 0.1095

p intercept -1.4576 0.4933 0.1888 0.0756

p Humid 7.8882 4.6394 0.9996 0.0017

Rana grylio

Best model: Psi (island), p (humid, temp, water)

Beta SE 95% CI lower 95% CI upper

Psi Intercept -0.7092 0.6263 0.3298 0.1384

Psi Island -59.2799 -1.3E+07 0 0

p intercept 6.7306 3.574 0.9988 0.0043

p Humid -50.919 -27.9418 0 0

p Temp -0.5067 0.207 0.376 0.0486

p Water -6.1256 2.6192 0.0022 0.0057

Appendix I–II 63
64 Herpetofaunal Inventory of Biscayne National Park

Rana sphenocephala

Best model: Psi (island), p (temp)

Beta SE 95% CI lower 95% CI upper

Psi Intercept 33.5623 0 1 0

Psi Island -61.6169 0 0 0

p intercept -3.0365 2.1547 0.0458 0.0942

p Temp 0.3612 12.0686 0.5893 2.9208

Sphaerodactylus notatus

Best model: Psi (.), p (humid, temp, water)

Beta SE 95% CI lower 95% CI upper

Psi Intercept -0.7396 0.5411 0.3231 0.1183

p intercept -3.4042 1.1788 0.0322 0.0367

p Humid 14.6034 9.0538 1 0

p Temp -0.3668 0.2155 0.4093 0.0521

p Water -19.8725 -10488.9 0 0

Appendix I. (Continued) Best models of proportion area occupied by species.

[% CI, percent confidence interval]
Appendix II. Biscayne National Park website list of reptiles present in the park.

Genus Species Subspecies Common Name

Alligator mississipiensis American alligator

Crocodylus acutus American crocodile

Elaphe guttata guttata Corn snake

Elaphe obsoleta rossalleni Everglades rat snake

Tantilla coronata wagneri Florida crowned snake

Sistrurus miliarius barbouri Dusky pigmy rattlesnake

Crotalus adamanteus Eastern diamondback rattlesnake

Drymarchon corais couperi Eastern indigo snake

Coluber constrictor paludicola Everglades racer

Terrapene carolina bauri Florida box turtle

Eumeces egregius egregius Florida Keys mole skink

Sphaerodactylus notatus notatus Florida reef gecko

Nerodia fasciata pictiventris Florida water snake

Anolis carolinensis Green anole

Micrurus fulvius fulvius Harlequin coral snake

Dermochleys coriacea Leatherback sea turtle

Scincella lateralis Ground skink

Hemidactylus turcicus Mediterranean house gecko

Tantilla oolitica Rim rock crowned snake

Opheodrys aestivus Rough green snake

Eumeces inexpectatus Southeastern five-lined skink

Seminatrix pygaea cyclas Southern Florida swamp snake

Diadophis punctatus punctatus Southern ringneck snake

Kinosternon baurii Striped mud turtle

Elaphe obsoleta quadrivittata Yellow rats nake

Appendix I–II 65