Ostodes strigatus

Species Report 

May 2020

U.S. Fish and Wildlife Service

Pacific Islands Fish and Wildlife Office

Honolulu, HI
ii
1 

Suggested Citation 

USFWS. 2020. Species Status Assessment for Ostodes strigatus. May 2020 (Version 1.1). U.S. 

Fish and Wildlife Service, Pacific Islands Fish and Wildlife Office, Honolulu, HI. 30 pp. 

Primary Authors

Version 1.1 of this document was prepared by Adam E. Vorsino, Fred Amidon and James 

Kwon of the Pacific Islands Fish and Wildlife Office, Honolulu, Hawaii. Preparation and review 

was conducted by Gregory Koob, Megan Laut, and Stephen E. Miller of the Pacific Islands Fish 

and Wildlife Office. 
2

Executive Summary

This Species Report summarizes the status of Ostodes strigatus, a tropical land snail endemic to 

the Samoan archipelago, based on the most recent information. For E. zebrina, this is 

information from Cowie and Cook, 1999.

To assess the viability of Ostodes strigatus we used the three conservation biology principles of 

resiliency, redundancy, and representation, or the “3Rs” (USFWS 2016, p 12-16). The viability 

of O. strigatus is evaluated with reference to the resiliency of its populations, its redundant 

occurrence across its native range, and its representation in its known habitat types. 

Ostodes strigatus, a tropical tree snail in the family Neocyclotidae (after Poteriidae) occurs 

solely on the island of Tutuila in American Samoa. The family consists of tropical land snails 

throughout Central America, the northern end of South America, and the South Pacific. The 

genus Ostodes is endemic to the Samoan archipelago. Ostodes strigatus is known from the 

western portion of the island of Tutuila (Girardi 1978, pp. 191, 242). Until 1975, it was 

considered widespread and common, but has declined significantly (Miller 1993, p. 15; Cowie 

2001, p. 215).

Systematic surveys conducted in and prior to 1998 suggest an overall decline in distribution and 

abundance of Ostodes strigatus, with western end of Tutuila (Maloata Valley) representing a 

large proportion of the known remaining populations of the species. Live individuals or shells of 

O. strigatus have not been reported since 1992, and no systematic surveys have been conducted 

for this species since the late 1990s (Cowie and Cook 1999, p. 24; Miles 2015c, in litt.).

Threats to Ostodes strigatus include; predation by Rats, Non-Native Tree Snails and Non-Native 

flatworms, habitat destruction due to agriculture, urban expansion, or non-native invasive plants, 

and stochastic processes such as extreme weather events. The synergistic effects of these threats 

is expected to influence the viability of O. strigatus more than any specific combination of them. 

Conservation efforts that may affect O. strigatus are focused solely on the control and removal of 

invasive plants from native ecosystems. Though there has been some effort to control Rats on 

outlying islets, current measures do not affect O. strigatus directly. Due to these factors, current 

viability of the species is expected to be low as Redundancy, Resilience and Representation of all 

known O. strigatus populations are low to non-existent. 
3

Table of Contents

Suggested Citation .......................................................................................................................... 1

Primary Authors.............................................................................................................................. 1

Executive Summary........................................................................................................................ 2

List of Tables .................................................................................................................................. 4

List of Figures................................................................................................................................. 4

Introduction..................................................................................................................................... 5

Regulatory History.......................................................................................................................... 5

Methodology................................................................................................................................... 5

Part 1. Life History and Historical Species Status.......................................................................... 8

Geography ................................................................................................................................... 8

Physical Environment ................................................................................................................. 9

Land-Use ..................................................................................................................................... 9

Biological Environment ............................................................................................................ 14

Species Description................................................................................................................... 16

Appearance ............................................................................................................................ 16

Measurements and Mass........................................................................................................ 17

Life History ............................................................................................................................... 17

Breeding Biology................................................................................................................... 17

Habitat ................................................................................................................................... 17

Historical Range........................................................................................................................ 17

Part 2. Current Conditions and Species Status.............................................................................. 18

Current Range and Distribution ................................................................................................ 18

Factors Affecting Viability........................................................................................................ 19

Habitat Loss and Degradation ............................................................................................... 19

Other Factors Affecting Viability .................................................................................... 23

Conservation Efforts that Affect Viability ............................................................................ 25

Resiliency, Redundancy and Representation of Current Populations and the Species............. 26

Literature Cited ............................................................................................................................. 27
4

List of Tables

TABLE 1. CENSUS ESTIMATES OF THE AMERICAN SAMOA POPULATION ON THE ISLANDS OF TUTUILA, TA’Ū, OFU,

OLOSEGA, AND SWAINS.......................................................................................................................................10

TABLE 2. CENSUS ESTIMATES OF THE SAMOA POPULATION BY ISLAND........................................................................10

TABLE 3.ESTIMATED ACREAGES OF MAJOR LAND COVER TYPES FOR THE SAMOAN ARCHIPELAGO. ACREAGES ARE IN 

ACRES WITH HECTARES IN PARENTHESIS..............................................................................................................13

TABLE 4. ESTIMATED ACREAGES OF VEGETATION TYPES FOR THE MAIN ISLANDS OF AMERICAN SAMOA. ACREAGES 

ARE IN ACRES WITH HECTARES IN PARENTHESIS. .................................................................................................16

TABLE 5. CURRENT SPECIES STATUS OF OSTODES STRIGATUS IN RELATION TO THE 3 R’S............................................26

List of Figures

FIGURE 1. THE THREE CONSERVATION BIOLOGY PRINCIPLES OF RESILIENCY, REDUNDANCY, AND REPRESENTATION, OR 

THE “3RS”. ............................................................................................................................................................6

FIGURE 2.MAP AND LOCATION OF THE ISLANDS IN THE SAMOAN ARCHIPELAGO. ..........................................................9

FIGURE 3. MONTHLY MEAN PRECIPITATION FOR SELECTED AREAS OF THE SAMOAN ARCHIPELAGO. ALL DATA PACIFIC 

CLIMATE CHANGE SCIENCE PROGRAM (PCCSP) (2019).....................................................................................11

FIGURE 4. MONTHLY MEAN TEMPERATURES FOR SELECTED AREAS OF THE SAMOAN ARCHIPELAGO. ALL DATA PACIFIC 

CLIMATE CHANGE SCIENCE PROGRAM (PCCSP) (2019).....................................................................................12

FIGURE 5.CYCLONE (HURRICANE)TRACKS FOR THE CENTRAL SOUTH PACIFIC FROM 1898 TO 2019. ALL DATA FROM 

KNAPP ET AL. (2010) AND NOAA IBTRACS (2019)...........................................................................................12

FIGURE 6.LOCATIONS OF ROADS IN THE SAMOAN ARCHIPELAGO. ................................................................................13

FIGURE 7. MAP OF VEGETATION ON AMERICAN SAMOA. DEVELOPED FROM DATA BY MEYER ET AL. (2017). .............15

FIGURE 8. MAP OF OSTODES STRIGATUS OBSERVATIONS AND VEGETATION ON AMERICAN SAMOA. DEVELOPED FROM 

DATA BY MEYER ET AL. (2017)............................................................................................................................18
5

Introduction

Ostodes strigatus, a tropical ground dwelling snail in the family Poteriidae, occurs solely on the 

island of Tutuila in American Samoa (Girardi 1978, pp. 193, 214; Miller 1993, p. 7). Ostodes 

strigatus is a member of the superfamily Cyclophoroidea and the family Poteriidae (= 

Neocyclotidae) (Cowie 1998, p. 24; Girardi 1978, p. 192; Vaught 1989, p. 16; Integrated 

Taxonomic Information System (ITIS) 2019). The family Poteriidae consists of tropical land 

snails throughout Central America, the northern end of South America, and the South Pacific. 

The genus Ostodes is endemic only to the Samoan archipelago (Girardi 1978, pp. 191, 242).

Regulatory History

The U.S. Fish and Wildlife Service issued a final listing rule in 2016, in which the Service 

determine endangered status under the Endangered Species Act of 1973, as amended, for two 

endemic American Samoan land snails (Eua zebrina and Ostodes strigatus), the American 

Samoa distinct population segment of the friendly ground-dove, the Pacific sheath-tailed bat, 

(South Pacific subspecies) (Emballonura semicaudata semicaudata), and the mao (Gymnomyza 

samoensis). The effect of this regulation added these species to the List of Endangered and 

Threatened Wildlife (U.S. Fish and Wildlife Service. 2016a). There are no additional regulatory 

documents for Ostodes strigatus, apart from a long list of Candidate Notice of Reviews 

(CNORs) annually from 2005 to 2014 and a proposed rule for listing in 2016. (Go to 

https://www.fws.gov/endangered/ and do a species search for Ostodes strigatus to get links to the 

CNORs, the proposed rule, and the final rule.)

Methodology

We used the best scientific and commercial data available to us, including peer-reviewed 

literature, gray literature (government, academic, business, and industry reports), and expert 

elicitation. Data gaps were addressed using data available for congeners or otherwise similar 

species, as well as using basic conservation biology principles and plant and animal biology to 

identify the needs of individuals, populations, and species.

This Species Report assesses the ability of Ostodes strigatus to maintain viability over time. 

Viability is the ability or likelihood of the species to maintain populations over time, i.e., 

likelihood of avoiding extinction. The viability of O. strigatus was assess using the three 

conservation biology principles of resiliency, redundancy, and representation, or the “3Rs” (Fig 

1; USFWS 2016b, p 12-16). The viability of O. strigatus was evaluated by describing what the 

snail needs to be resilient, redundant, and represented, followed by comparing this assessment of 

what is needed for viability to the status of the snail in its current condition or its condition based 

on the most recent information. For O. strigatus, the most recent is from Cowie and Cook, 1999.
6

Figure 1. The three conservation biology principles of resiliency, redundancy, and 

representation, or the “3Rs”.

The definitions of the “3Rs” are defined below, and are used to infer the status of the species.

• Resiliency is the capacity of a population or a species to withstand the more extreme 

limits of normal year-to-year variation in environmental conditions such as temperature 

and rainfall extremes, and unpredictable but seasonally frequent perturbations such as 

fire, flooding, and storms (i.e., environmental stochasticity). Quantitative information on 
7

the resiliency of a population or species is often unavailable. However, in the most 

general sense, a population or species that can be found within a known area over an 

extended period of time (e.g., seasons or years) is likely to be resilient to current 

environmental stochasticity. If quantitative information is available, a resilient population 

or species will show enough reproduction and recruitment to maintain or increase the 

numbers of individuals in the population or species, and possibly expand the range of 

occupancy. Thus, resiliency is positively related to population size and growth rate, and 

may also influence the connectivity among populations. 

• Redundancy is having more than one resilient population distributed across the 

landscape, thereby minimizing the risk of extinction of the species. To be effective at 

achieving redundancy, the distribution of redundant populations across the geographic 

range should exceed the area of impact of a catastrophic event that would otherwise 

overwhelm the resilient capacity of the populations of a species. In the report, 

catastrophic events are distinguished from environmental stochasticity in that they are 

relatively unpredictable and infrequent events that exceed the more extreme limits of 

normal year-to-year variation in environmental conditions (i.e., environmental 

stochasticity), and thus expose populations or species to an elevated extinction risk within 

the area of impact of the catastrophic event. Redundancy is conferred upon a species 

when the geographic range of the species exceeds the area of impact of any anticipated 

catastrophic event. In general, a wider range of habitat types, a greater geographic 

distribution, and connectivity across the geographic range will increase the redundancy of 

a species and its ability to survive a catastrophic event.

• Representation is having more than one population of a species occupying the full range 

of habitat types used by the species. Alternatively, representation can be viewed as 

maintaining the breadth of genetic diversity within and among populations, in order to 

allow the species to adapt to changing environmental conditions over time. The diversity 

of habitat types, or the breadth of the genetic diversity of a species, is strongly influenced 

by the current and historic biogeographical range of the species. Conserving this range 

should take into account historic latitudinal and longitudinal ranges, elevation gradients, 

climatic gradients, soil types, habitat types, seasonal condition, etc. Connectivity among 

populations and habitats is also an important consideration in evaluating representation.

The viability of a species is derived from the combined effects of the 3Rs. A species is 

considered viable when there are a sufficient number of self-sustaining populations (resiliency) 

distributed over a large enough area across the range of the species (redundancy) and occupying 

a range of habitats to maintain environmental and genetic diversity (redundancy) to allow the 

species to persist indefinitely when faced with annual environmental stochasticity and infrequent 

catastrophic events. Common ecological features are part of each of the 3Rs. This is especially 

true of connectivity among habitats across the range of the species. Connectivity sustains 

dispersal of individuals, which in turn greatly affects genetic diversity within and among 

populations. Connectivity also sustains access to the full range of habitats normally used by the 
8

species, and is essential for re-establishing occupancy of habitats following severe environmental 

stochasticity or catastrophic events (see Fig 1. for more examples of overlap among the 3Rs). 

Another way the three principles are inter-related is through the foundation of population 

resiliency. Resiliency is assessed at the population level, while redundancy and representation 

are assessed at the species level. Resiliency populations are the necessary foundation needed to 

attain sustained or increasing Representation and Redundancy within the species. The assessment 

of viability is not binary, in which a species is either viable or not, but rather on a continual scale 

of degrees of viability, from low to high. The health, number and distribution of populations 

were analyzed to determine the 3Rs and viability. In broad terms, the more resilient, represented, 

and redundant a species is, the more viable the species is. The current understanding of factors, 

including threats and conservation actions, will influence how the 3Rs and viability are 

interpreted for Ostodes strigatus.

Part 1. Life History and Historical Species Status

Geography

The Samoan archipelago consists of a remote chain of 13 islands and 2 atolls in the Pacific 

Ocean south of the equator (Figure 2). These islands extend more than 298 miles (mi) (480 

kilometers (km)), lying between 13 and 15 degrees south latitude, and 168 to 172 degrees west 

longitude (Goldin 2002, p. 4). The islands date to the early Pleistocene and were formed as hotspot shield volcanoes, with the older islands located on the western end of the chain (ThornberyEhrlich 2008), pp. 16, 28). The archipelago is divided into two political entities, American 

Samoa, an unincorporated territory of the United States, and the independent nation of Samoa 

(Craig 2009, p. 5). The Samoan archipelago lies approximately 2,600 miles (4,184 km 

southwest of Hawaii (Goldin 2002, p. 4).

American Samoa consists of five high islands and two atolls: Tutuila (the largest island; 54 

square (sq) mi (140 sq km)); Aunuu (1 sq mi (2 sq km)) off the southeast end of Tutuila; Ofu and 

Olosega (3.5 sq mi (9 sq km)) separated by a narrow channel now spanned by a bridge; Ta‘ū (15 

sq mi (39 sq km)); Rose Atoll (1.5 sq mi (4 sq km)), a National Wildlife Refuge) with two 

uninhabited islands, Rose and Sand; and Swains Island (0.6 sq mi (1.5 sq km)), which is 

politically part of American Samoa, but geologically and biologically part of the Tokelau 

archipelago. These islands and atolls range in elevation from the high peak of Mt. Lata on Ta‘ū

at 3,170 feet (ft) (966 meters (m)) to 4 to 6 ft (1 to 2 m) above sea level (asl) at Rose Atoll

(Goldin 2002, pp. 5-6). 
9

Figure 2.Map and location of the Islands in the Samoan archipelago.

Physical Environment

The Samoan archipelago lies within the tropics, where it is hot, humid, and rainy year-round. 

The wet season is from October to May, with a slightly cooler and drier season from June 

through September (Figures 3 and 4). Temperatures average about 81.5 degrees Fahrenheit (F) 

(27 degrees Celsius (C)) at lower elevations. Rainfall averages 125 inches (in) (318 centimeters 

(cm)) annually at lower elevations, but can vary greatly depending upon topography, reaching 

300 in (750 cm) or greater annually in the mountain areas. Tropical cyclones (called hurricanes 

or typhoons north of the equator) are a common natural disturbance in the Samoan Archipelago 

(Figure 5), and occur at intervals of between 1 to 13 years (Goldin 2002, p. 7).

Land-Use

In 2010/2011, the population of American Samoa and Samoa was 55,519 and 187,820, 

respectively (U. S. Census Bureau 2010; Samoa Bureau of Statistics (SBS) 2011, p. 14). Ninetyeight percent of the American Samoa population occurs on the island of Tutuila (Table 1) while 

76% of the Samoa population occurs on ‘Upolu (which includes Manono and Apolima islands, 

Table 2). Census data collected since 1920 for American Samoa shows initial increases in 

populations on the Manu‘a Islands (Ta‘ū, Ofu and Olosega) and then declines by 2010 (Table 1). 

Tutuila shows a steadily increasing population from 1920 to 1980 and then some fluctuation in 

subsequent years. Samoa shows a steadily increasing population from 1951 to 2011with the 

population on Savai‘i remaining stable from 1981 to 2016 while ‘Upolu shows a steady increase 

during that period (Table 2).
10

Table 1. Census estimates of the American Samoa population on the islands

of Tutuila, Ta’ū, Ofu, Olosega, and Swains.

Year American 

Samoa

Island

Tutuila Ta‘ū Ofu Olosega Swains Island

19201 8,056 6,185 1,155 361 355 -

19301,2 10,055 7,809 1,243 466 438 99

19401,2 12,908 10,164 1,588 500 509 147

19501,2 18,937 15,954 1,698 576 545 164

19602 20,051 17,250 1,661 605 429 106

19703 27,159 24,973 1,320 412 380 74

19803 47,283 45,524 1,138 345 249 27

19904 46,773 45,043 1,136 353 225 16

20005 57,291 55,876 873 289 216 37

20105 55,519 54,359 790 176 177 17

1

Unkown (1956) , 2 Levin and Wright (1974), 3 U. S. Census Bureau (1982), 4 U. S. 

Census Bureau (1992), 5 U. S. Census Bureau (2010)

Table 2. Census estimates of the Samoa population by island 

and for the entire country.

Year1 Samoa Island

‘Upolu Savai‘i

1951 84,909 - -

1961 114,427 - -

1971 146,647 - -

1981 156,349 113,199 43,150

1991 161,298 116,248 45,050

2001 176,710 133,886 42,824

2011 187,820 143,418 44,402 1

All data from Samoa Bureau of Statistics (SBS) (2011 p. 14, 17)

Due to the steep topography of the islands, human habitation is primarily located along the 

coastlines (Figure 6). On American Samoa, small-scale agriculture occurs inland from villages in 

former lowland rainforest areas on slopes that sometimes exceed 45 degrees (Atkinson and 

Medeiros 2006, p. 4). Approximately 11% (5,456 acres, 2,208 hectares) of American Samoa and 

3% (21,869 acres, 8,850 hectares) of Samoa are classified as developed (i.e., urban areas, roads, 

infrastructure; Table 3). In contrast, 6% (2,824 acres, 1,143 hectares) of American Samoa and 

25% (174,449 acres, 70,597 hectares) of Samoa are classified as agriculture (Table 3). The 

majority of the development and agriculture in American Samoa occurs on Tutuila where the 

largest human population resides (Table 1 and Table 3). A similar pattern occurs in Samoa, 

where the majority of the development and agriculture occurs on ‘Upolu, where the majority of 

the human population resides (Table 2 and Table 3).
11

Figure 3. Monthly mean precipitation for selected areas of the Samoan archipelago. All data

Pacific Climate Change Science Program (PCCSP) (2019).
12

Figure 4. Monthly mean temperatures for selected areas of the Samoan archipelago. All data

Pacific Climate Change Science Program (PCCSP) (2019).

Figure 5.Cyclone (hurricane)tracks for the central South Pacific from 1898 to 2019. All data 

from Knapp et al. (2010) and NOAA IBTrACS (2019).
13 

Figure 6.Locations of roads in the Samoan archipelago. 

Table 3.Estimated acreages of major land cover types for the Samoan archipelago. Acreages are 

in acres with hectares in parenthesis. 

1 All data from (Meyer et al. 2017)and the Ministry of Natural Resources & Environment (MNRE) (2014). 

Land cover1

Samoa American Samoa

Savai‘i ‘Upolu Minor Islands Tutuila Ofu/ 

Olosega Ta‘ū

Developed 6,934 (2,806) 14,794 (5,987) 141 (57) 5,179 (2,096) 101 (41) 175 (71)

Agriculture 77,905 (31,527) 96,037 (38,865) 507 (205) 2,664 (1,078) 42 (17) 119 (48)

Forest 281,593 

(113,957) 124,830 (50,517) 722 (292) 23,262 (9,414) 2,797 (1,132) 8,300 (3,359)

Scrub 29,734 (12,033) 17,957 (7,267) 171 (69) 1,564 (633) 52 (21) 1,873 (758)

Grassland/ 

Herbaceous 16,131 (6,528) 21,730 (8,794) 37 (15) 440 (178) 35 (14) 625 (253)

Mangrove 67 (27) 801 (324) 15 (6) 79 (32) 0 (0) 0 (0)

Wetland 306 (124) 726 (294) 67 (27) 72 (29) 7 (3) 17 (7)

Open Water 91 (37) 692 (280) 10 (4) 62 (25) 0 (0) 0 (0)

Barren 7,811 (3,161) 247 (100) 49 (20) 432 (175) 94 (38) 128 (52)
14

Biological Environment

Mueller-Dombois and Fosberg (1998, p. 361) describes seven general categories of vegetation in 

the Samoan archipelago: 

• Littoral vegetation generally refers to vegetation that is directly exposed to salt spray and 

occurs along the coasts. It includes a variety of forest, scrub, and herbaceous 

communities (see Whistler (1992) and Mueller-Dombois and Fosberg (1998) for detailed 

descriptions). 

• Lowland rainforests occur below approximately 1,600-2,000 ft (500-600 m) elevation 

and include a variety of subtypes based on the dominate canopy species. 

• Montane rainforests occur above 1,600-2,000 ft (500-600 m) elevation and are generally 

cooler and rainier then lowland forests. 

• Cloud forest and cloud scrub is limited to Savai‘i, ‘Upolu, Ta‘ū and Olosega and are 

wetter than montane forests due to the persistence of clouds. 

• Wetland vegetation includes mangroves, swamp forest, coastal marsh, and montane

marsh and bog areas. Montane marsh and bog areas are limited to Savai‘i and ‘Upolu. 

• Vegetation on recent volcanic surfaces includes scrubby woody vegetation, ferns, and 

grasses that may represent pioneer rainforest. 

• Modified vegetation includes all areas that were formerly dominated by native vegetation 

but were altered due to human activity (e.g., urban areas, agriculture areas, secondary 

forest, etc.). 

Approximately 70% of American Samoa is forested with the majority classified as lowland 

tropical rainforest (Figures 3, 4, and 7, Tables 3 and 4). Montane rainforest makes up a smaller 

percent of the forest areas and is primarily restricted to Ta‘u with a small amount on Tutuila 

(Figure 7, Table 4). Approximately 58% of Samoa is also forested (Table 3). The native flora of 

the Samoan archipelago (plant species that were present before humans arrived) consisted of 

approximately 550 taxa, 30 percent of which were endemic (species that occur only in the 

American Samoa and Samoa) (Whistler 2002, p. 8). An additional 250 plant species have been 

intentionally or accidentally introduced and have become naturalized with 20 or more of these 

considered invasive or potentially invasive in American Samoa (Whistler 2002, p. 8; Space and 

Flynn 2000, pp. 23-24). 
15

Figure 7. Map of vegetation on American Samoa. Developed from data by Meyer et al. (2017).
16

Table 4. Estimated acreages of vegetation types for the main islands of American Samoa. 

Acreages are in acres with hectares in parenthesis. 

1 Data from Meyer et al. (2017).

Species Description

Ostodes strigatus is a member of the superfamily Cyclophoroidea and the family Neocyclotidae

(=Poteriidae) (Cowie 1998, p. 24; Girardi 1978, p. 192; Vaught 1989, p. 16; Integrated 

Taxonomic Information System (ITIS) 2019). The family consists of tropical land snails 

throughout Central America, the northern end of South America, and the South Pacific. The 

genus Ostodes is endemic to the Samoan archipelago (Girardi 1978, pp. 191, 242).

Appearance

The defining characteristics of species within the family Poteriidae include a pallium cavity 

(lung-like organ) and an operculum (a shell lid or ‘‘trap door’’) used to close the shell aperture 

when the snail withdraws inward (Girardi 1978, pp. 214, 222–224; Vaught 1989, p. 16; Barker 

2001, pp. 15, 25). The operculum of Ostodes strigatus is acutely concave to cone-shaped, with 

broad, irregular spirals from center to edge (Girardi 1978, pp. 198, 213, 222–224). True radial 

Type1 Subtype Tutuila Aunu‘u Ofu/Olesega Ta‘ū

Littoral

Vegetation

Herbaceous 

Strand 26 (11) 22 (9) 1 (<1) 572 (231)

Littoral Forest 608 (246) 35 (14) 295 (119) 338 (137)

Littoral Scrub 117 (47) 4 (2) 9 (4) 17 (7)

Pandanus Scrub 18 (7) 0 (0) 0(0) 0

(0)

Wetland

Vegetation

Coastal Marsh 7 (3) 34 (14) 7 (3) 7 (3)

Mangrove Scrub 

& Forest 79 (32) 14 (6) 0 (0) 0 (0)

Swamp Forest 64 (26) 29 (12) 0 (0) 10 (4)

Lowland 

Rainforest - 20,507 (8,299) 0 (0) 480(194) 761 (308)

Montane 

Rainforest - 95 (38) 0 (0) 92 (37) 2,809 (1,137)

Cloud Forest & 

Scrub - 0 (0) 0 (0) 0 (0) 546 (221)

Vegetation on 

Recent Volcanic 

Surfaces

- 223 (90) 0 (0) 0 (0) 0 (0)

Modified 

Vegetation

Fernlands 3 (1) 2 (1) 13 (5) 34 (14)

Managed Land 10,296 (4,167) 139 (56) 406 (164) 513 (208)

Secondary 

Forest 0 (0) 53 (22) 1,696 (686) 5,421 (2,194)

Secondary 

Scrub 1,214 (491) 14 (6) 37 (15) 78 (31)

Open Water - 62 (25) 11 (4) 0 (0) 0 (0)

Terrestrial

Non-vegetated - 431 (175) 18 (7) 93 (38) 129 (52)
17

patterning is seldom found on the upper shell surface, and never on the ventral surface, which is 

usually entirely smooth (Girardi 1978, p. 223).

Measurements and Mass

Ostodes strigatus has a white, turbinate (depressed conical) shell with 4 to 5 whorls and 

distinctive parallel ridges, reaching a size of 0.3 to 0.4 in (7 to 11 mm) in height and 0.4 to 0.5 in 

(9 to 12 mm) in diameter at maturity (Girardi 1978, pp. 222–223; Abbott 1989, p. 43).

Life History

Although the biology of the genus Ostodes is not well studied and therefore the exact diet is 

unknown, it is highly probable that O. strigatus feeds at least in part on decaying leaf litter and 

fungus (Girardi 1978, p. 242).

Breeding Biology

The approximate age at which O. strigatus reach full sexual maturity is unknown (Girardi 1978, 

p. 194). Once they reach maturity and can successfully reproduce, it is likely adult snails deposit 

their eggs into leaf litter where they develop and hatch.

Habitat

Ostodes strigatus is found on the ground in rocky areas under relatively closed canopy with 

sparse understory plant coverage at elevations below 1,280 ft (390 m) (Girardi 1978, p. 224; 

Miller 1993, pp. 13, 15, 23, 24, 27). Moisture supply is the principal environmental influence on 

Ostodes land snails (Girardi 1978, p. 245). The degree of moisture retention is controlled 

primarily by vegetation cover, with heavy forest retaining moisture at ground level longer than 

open forest or cleared areas (Girardi 1978, p. 245).

Ostodes species were collected only in areas with heavy tree cover (Solem pers. comm. in 

Girardi 1978, p. 245), but the relative importance of rainfall and soil type in maintaining 

moisture supply was not assessed in these areas (Girardi 1978, p. 245). Nevertheless, relatively 

closed canopy or heavy tree cover and their roles in maintaining moisture supply appears to be 

an important habitat factor for O. strigatus.

Historical Range

Until 1975, Ostodes strigatus was considered widespread and common, but has since declined 

significantly (Miller 1993, p. 15; Cowie 2001b, p. 215). In 1992, a survey of nine sites on Tutuila 

reported several live individuals (and abundant empty shells) from a single site on the western 

end of the island (Maloata Valley) and only shells (no live individuals) at three sites in the 

central part of the island (Miller 1993, pp. 23–27). At each of the four sites where live O. 

strigatus or empty shells were found, the predatory rosy wolf snail was common or abundant 

(Miller 1993, p. 23). In 1998, surveys within the newly established National Park of American 

Samoa (NPAS) on northern Tutuila did not detect any live O. strigatus or shells (Cowie and 
18

Cook 2001, pp. 143–159); however, Cowie and Cook (1999, p. 24) note that these areas were 

likely outside the range of O. strigatus. We are unaware of any surveys conducted for this 

species since 1998; however, local field biologists that frequent the forest above Maloata Valley 

for other biological field work report they have not seen O. strigatus (Miles 2015c, in litt.). 

Observations of live individuals at a single location on western Tutuila more than 20 years ago 

suggest that this species has undergone a significant reduction in its range and numbers (Miller 

1993, pp. 15, 23–27; Cowie 2001b, p. 215). Live individuals or shells of O. strigatus have not 

been reported since 1992, and no systematic surveys have been conducted for this species since

the late 1990s (Cowie and Cook 1999, p. 24; Miles 2015c, in litt.).

Part 2. Current Conditions and Species Status

Current Range and Distribution

Ostodes strigatus is known only from the western portion of the island of Tutuila in American 

Samoa, including the center and southeast edge of the central plateau, and the extreme southern 

coast and mountain slope near Pago Pago, (Figure 8) with an elevation range of 60 to 390 m (197 

to 1,280 ft) (Girardi 1978, p. 224; Bishop Museum 2019).

Figure 8. Map of Ostodes strigatus observations and vegetation on American Samoa. Developed 

from data by Meyer et al. (2017).
19

Factors Affecting Viability

Habitat Loss and Degradation

The following sections provide information on habitat loss and degradation due to agriculture 

and development, introduced feral pigs, introduced predatory snails, and introduced plants.

Habitat Destruction and Modification by Agriculture and Development

Several thousand years of subsistence agriculture and more recent plantation agriculture has 

resulted in the alteration and reduction in forest area on lower elevation arable land throughout 

American Samoa (Whistler 1994, p. 40; Mueller-Dombois and Fosberg 1998, p. 361). Fifty-five 

percent of the island of Tutuila has slopes of less than 45 percent where land-clearing for 

agriculture or development is feasible (ASCC Forestry Program 2010, p. 13; Department of 

Marine and Wildlife Resources 2006). Currently, agriculture and urban development covers 

approximately 23 percent of Tutuila and three to four percent of the Manu‘a Islands of American 

Samoa (Ofu, Olosega, and Ta‘u). 

Farmers are increasingly encroaching on steep forested areas, and agriculture on Tutuila has 

spread from low elevation plots to plots in middle and high elevation areas (ASCC 2010, p. 13). 

Agricultural area on Tutuila has expanded by 59% (from 1,675 acres to 2,664 acres) since 1970, 

but decreased by 68% (from 507 acres down to 161 acres) on the Manu‘a Islands (Ofu, Olosega, 

and Ta‘u) (Pereira, 1981 p. 68; Ministry of Natural Resources & Environment (MNRE), 2014, 

Table 1). This loss of forest area likely reduces habitat resilience, and may directly contribute to 

the decline of Ostodes strigatus through the loss of populations of native snails. An increase in 

housing is also projected to occur in some areas (Stein et al. 2014, p. 24). 

The development of roads, trails, and utility corridors has also caused habitat destruction and 

modification in or adjacent to populations of Ostodes strigatus on Tutuila (Cowie and Cook 

1999, pp. 3, 30). Development and agriculture on Tutuila is increasing. The population and 

agricultural land area on this island has increased by approximately 118% (Table 1) and 59% 

(Pereira, 1981 p. 68), respectively, since 1970. In addition, construction activities, regular 

vehicular and foot trail access, and road maintenance activities cause erosion and the increased 

spread of nonnative plants resulting in further destruction or modification of habitat (Cowie and 

Cook 1999, pp. 3, 47–48).

Land conversion to agriculture on steeper topography at elevations above the coastal plain will 

accelerate if the human population continues to grow, or if changes in the economy shift toward 

commercial agriculture (Department of Marine and Wildlife Resources 2006, p. 71). This is 

especially true for Tutuila. 

Habitat Destruction and Modification by Nonnative Plant Species

Nonnative plant species can adversely modify native habitat and render it unsuitable for native 

snail species (Hadfield 1986, p. 325). Although some Hawaiian tree snails have been recorded on 

nonnative vegetation, it is more generally the case that native snails throughout the Pacific are 

specialized to survive only on the native plants with which they have evolved, with few 

observations of native snails in disturbed habitats on Tutuila (Cowie 2001, p. 219). 
20

Nonnative plants can degrade or destroy native habitat in Pacific island environments by: (1) 

modifying light availability by altering canopy structure; (2) altering soil–water regimes; (3) 

modifying nutrient cycling; (4) converting native-dominated plant communities to nonnative 

plant communities; and (5) increasing the frequency of landslides and erosion (Smith et al. 1985, 

pp. 217–218; Cuddihy and Stone 1990, p. 74; Matson 1990, p. 245; D’Antonio and Vitousek 

1992, p. 73; Vitousek et al. 1997, pp. 6– 9; Atkinson and Medeiros 2006, p. 16). Nonnative plant 

species often exploit disturbance caused by other factors such as tropical cyclones (hurricanes), 

agriculture, development, and feral ungulates. In combination, these disturbances reinforce or

exacerbate their negative impacts to native habitats. 

Although the island of Tutuila contain many areas that are relatively free of human disturbance 

and nonnative plant invasion and largely represent pre-contact vegetation, the threat of invasion 

and further spread by nonnative plant species is of concern (Space and Flynn 2000, pp. 23–24; 

Craig 2009, pp. 94, 96– 98; Atkinson and Medeiros 2006, p. 17; ASCC Forestry Program 2010, 

pp. 15, 20). Of the approximately 20 or more nonnative pest plant species in American Samoa, at 

least 10 (see below) have altered or may alter the habitat of Ostodes strigatus). The following 

provides a brief description of these nonnative pest plants (Atkinson and Medeiros 2006, p. 18; 

Space and Flynn 2000, pp. 23–24; Craig 2009, pp. 94, 96–98; ASCC Forestry Program 2010, p. 

15):

• Adenanthera pavonina (red bean tree, coral bean tree, lopa), native to India and Malaysia, 

is a medium-sized tree up to 50 ft (15 m) high that invades intact forests as well as 

disturbed sites, and can quickly form large stands (GISD 2006). In American Samoa, it is 

invasive in secondary forests, but also has the ability to become more widely established 

on Tutuila and the Manu‘a Islands (Space and Flynn 2000, p. 4). It is considered to have 

negative impacts on the native forests in American Samoa because the trees produce 

large quantities of seed, grow on a variety of soils, and can overtop many native trees and 

eventually form monotypic stands (Space and Flynn 2002, p. 5).

• Castilla elastica (Mexican rubber tree, pulu mamoe), native to tropical America, is a 

medium-sized tree 15 to 30 ft (5 to 10 m) high that can invade intact forest where it 

reproduces prolifically and can crowd out native species (National Park of American 

Samoa 2012, in litt.). It has displaced significant areas of lowland forest in Samoa, and is 

now considered to be an important threat to native forests in American Samoa (Atkinson 

and Medeiros 2006, p. 18).

• Cinnamomum verum (cinnamon, tinamoni), native to south Asia, is a fast-growing, 

medium-sized tree up to 30 ft (9 m) high with aromatic bark and leaves. It forms dense 

root mats that inhibit establishment of other plants, and can shade out other tree species 

and thus create monotypic stands. On Tutuila, it is actively spreading in the ridge forests 

of Mt. Matafao, Matuu, and Maloata (Space and Flynn 2000, p. 4; National Park of 

American Samoa 2012, in litt.).

• The shrub Clidemia hirta (Koster's curse), native to the New World from Mexico to 

Argentina, grows to be 6.6 ft (2 m) in height, forms a dense understory, shades out native 

plants, and prevents their regeneration (Wagner et al. 1985, p. 41; Smith 1989, p. 64). On 
21

Ta‘ū, it has become a serious problem in the unique summit scrub community (Whistler 

1992, p. 22).

• Falcataria moluccana (albizia, tamaligi) is native to Moluccas, New Guinea, New 

Britain, and the Solomon Islands and is established in American Samoa. It is a tree that 

can reach 131 ft (40 m) in height and has a wide-spreading canopy. It grows rapidly and 

outcompetes slow-growing native trees by reducing light availability, and its abundant, 

high-nutrient litter alters soil chemistry (GISD 2008). Its shallow root system may lead to 

soil instability and landslides (Atkinson and Medeiros 2006, p. 17). 

• Funtumia elastica (African rubber tree, pulu vao), is a medium-sized tree up to 100 ft 

(30 m) tall native to tropical Africa (U.S. Department of Agriculture–Agricultural 

Research Service (USDA) 2006). This tree is invasive because of its “parachute seeds” 

that can disperse long distances and germinate in sunny or shady conditions (Whistler 

2002, p. 122). Funtumia has become a dominant subcanopy and understory tree in the 

western half of Upolu where it can form monotypic forests (Pearsall and Whistler 1991, 

p. 30). It is also established and becoming dominant on eastern Savaii (Whistler 2002, p. 

122). This species has the potential to become a major problem in American Samoa due 

to its proximity and the volume of traffic with Samoa (Space and Flynn 2000, p. 12).

• Leucaena leucocephala (wild tamarind, lusina, fua pepe), a shrub native to the 

neotropics, is a nitrogen-fixer and an aggressive competitor that often forms the dominant 

element of the vegetation (Geesink et al. 1999, pp. 679–680). It crowds out native 

species and re-sprouts vigorously after cutting, and seeds can remain viable for 10 to 20 

years (Craig 2009, p. 98). It is established in American Samoa.

• Merremia peltata (Merremia, fue lautetele), is indigenous to the Samoan Archipelago 

where it is a sprawling, or high-climbing vine that can invade areas following 

disturbances such as land-clearing and tropical cyclones (hurricanes). This fast-growing 

vine can smother plantation and forest trees (Craig 2009, p. 98).

• Mikania micrantha (mile-a-minute vine, fue saina), native to tropical America, is a 

scrambling or climbing herbaceous vine, that retards forest regeneration with its 

smothering growth (Whistler 1994, p. 42). This sun-loving, shade-intolerant vine is a 

major pest of plantations and forests on all major American Samoa islands (Space and 

Flynn 2000, p. 5; Craig 2009, p. 94).

• Psidium cattleianum (strawberry guava, kuava) is a tall shrub or small tree that forms 

dense stands in which few other plants can grow, displacing native vegetation through 

competition. The fruit is eaten by feral pigs and birds that disperse the seeds throughout 

the forest (Smith 1985, p. 200; Wagner et al. 1985, p. 24). It is thought to have been 

cultivated in American Samoa for more than 40 years and has become naturalized in 

lowland rainforest on western Tutuila.

• Spathodea campanulata (African tulip, faapasi), native to tropical Africa, is a large tree 

up to 80 ft (24 m) or more in height with showy red-orange tulip-like flowers and pods 

containing hundreds of wind-dispersed seeds (Pacific Ecosystems At Risk (PIER) 2016). 

It is established in American Samoa and is particularly invasive in low-to mid-elevation 
22

forests, and can spread in open agricultural land, waste areas, and intact native forest, 

forming dense stands that shade out other vegetation (GISD 2010).

Predation by Nonnative Snails

At present, the primary threat to long-term survival of the native snail fauna in American Samoa 

is predation by the nonnative rosy wolf snail (Euglandina rosea), the most commonly 

recommended biological control agent of the giant African snail (Achatina fulica), which also is 

an invasive nonnative species in American Samoa. Numerous studies show that the rosy wolf 

snail feeds on endemic island snails and is a causal factor in their decline and extinction

(Hadfield and Mountain 1980, p. 357; Howarth 1983, p. 240, 1985, p. 161, 1991, p. 489; Clarke 

et al. 1984, pp. 101–103; Hadfield, Miller, and Carwile 1993, p. 327, pp. 616-620; Murray et al.

1982 pp. 150–153; Cowie 2001b, p. 219). 

In 1980, the rosy wolf snail was released on Tutuila to control the giant African snail (Lai and 

Nakahara 1980 as cited in Miller (1993, p. 9). By 1984, the rosy wolf snail was considered to be 

well established on Tutuila, having reached the mountains (Eldredge 1988, pp. 122, 124–125), 

and by 2001 was reported as widespread within the NPSA on Tutuila (Cowie and Cook 2001, pp. 

156–157). Live individuals of the rosy wolf snail have been observed within meters of tree snails 

on Tutuila (Miller 1993, p. 10). Shells of O. strigatus were found on the ground at several of the 

locations surveyed on Tutuila, along with numerous shells and an occasional live individual of 

the rosy wolf snail (Miller 1993, pp. 13, 23–28). 

Predation by several other nonnative carnivorous snails, Gonaxis kibweziensis, Streptostele 

musaecola, and Gulella bicolor, are also a threat to O. strigatus and other native land snails. Like 

the rosy wolf snail, species of Gonaxis were also widely introduced in the Pacific in attempts to 

control the giant African snail. These species have been implicated in contributing to the decline 

of native snail species in the region (Cowie and Cook 1999, p. 46). Gonaxis kibweziensis was 

introduced on Tutuila in American Samoa in 1977 (Eldredge 1988, p. 122). This species has 

been reported only from Tutuila (Miller 1993, p. 9, Cowie and Cook 1999, p. 36) and is not as 

common as the rosy wolf snail (Miller 1993, p. 11). 

Two other predatory snails have been recorded on the Manua Islands: S. musaecola from Tutuila, 

Ta‘ū, and Ofu; and G. bicolor on Ofu (Cowie and Cook 1999, pp. 36–37). The potential impacts 

of these two species on the native fauna are unknown; both are much smaller than the rosy wolf 

snail and G. kibweziensis and were rarely observed during surveys (Cowie and Cook 1999, pp. 

36–37, 46). However, Solem (1975 as cited in Miller 1993, p. 16) speculated that S. musaecola

might have a role in the further decline of native species, and Miller (1993, p. 16) considered that 

it ‘‘undoubtedly had a negative impact.’’ 

Predation by the New Guinea or Snail- Eating Flatworm

Predation by the nonnative New Guinea or snail-eating flatworm (Platydemus manokwari) is a 

threat to Ostodes strigatus. The extinction of native land snails on several Pacific Islands has 

been attributed to this terrestrial flatworm, native to western New Guinea (Ohbayashi et al. 2007, 

p. 483;Sugiura 2010, p. 1,499). The New Guinea flatworm was released in an unsanctioned 
23

effort to control the giant African snail (Achatina fulica) in Samoa in the 1990s (Cowie and Cook 

1999, p. 47). In 2002, this species was likely present within the Samoan archipelago but was not 

yet introduced to American Samoa (Cowie 2001b, p. 18). However, by 2004, this predatory 

flatworm had been found on the islands of Tutuila and Ta‘ū (Craig 2009, p. 84).

Although mostly ground-dwelling, the New Guinea flatworm has also been observed climbing 

trees to feed on partulid tree snails (Hopper and Smith 1992, p. 82). The New Guinea flatworm 

has contributed to the decline of native land and tree snails (Sugiura and Yamaura 2010, p. 741). 

Areas with populations of the flatworm usually lack, or have declining numbers, of snails 

(Hopper and Smith 1992, p. 82). Because Ostodes. strigatus feeds on the ground, it faces 

increased risk of predation by the New Guinea flatworm (Cooke 1928, p. 6). 

Predation by Rats

Rats are known to prey upon arboreal snails endemic to the Pacific islands, and they can 

devastate native snail populations (Hadfield et al., 1993, p. 621). Rat predation on tree snails has 

been observed on the Hawaiian Islands of Lāna‘i (Hobdy 1993, p. 208; Hadfield 2005, in litt., p. 

4; Hadfield and Saufler 2009, in litt, p. 4), Moloka‘i (Hadfield and Saufler 2009, p. 1,595), 

O‘ahu (Hadfield et al., 1993, p. 616) and Maui (Hadfield 2006, in litt.). Three species of rats are 

present in American Samoa: The Polynesian rat (Rattus exulans), probably introduced by early 

Polynesian colonizers, and Norway (R. norvegicus) and black ( R. rattus) rats, both introduced 

subsequent to western contact (Atkinson 1985, p. 38; Cowie and Cook 1999, p. 47; Department 

of Marine and Wildlife Resources 2006, p. 22). Polynesian and Norway rats are abundant in 

American Samoa, but insufficient data exist on the populations of black rats (Department of 

Marine and Wildlife Resources 2006, p. 22).

Frequent evidence of predation by rats on Samoan tree snails was observed at several locations 

on Tutuila (Miller 1993, pp. 13, 16); shells were damaged in a fashion that is typical of rat 

predation, the shell is missing a large piece of the body whorl or the apex (Miller 1993, p. 13). 

Frequent evidence of rat predation on native snails was also observed during subsequent surveys 

(Cowie and Cook 1999, p. 47). 

Other Factors Affecting Viability

Tropical Cyclones (Hurricanes)

Tropical cyclones are a common natural disturbance in the tropical Pacific and have impacted 

American Samoa with varying frequency and intensity (Figure 5). Hurricanes adversely affect 

ground snail and tree snail habitat by destroying vegetation, opening the canopy, and modifying 

light intensity and moisture, leading to the formation of disturbed areas that are open to invasion 

by nonnative plant species (Elmqvist et al. 1994, p. 387; Asner and Goldstein 1997, p. 148; 

Harrington et al. 1997, pp. 539–540; Lugo 2008, pp. 373–375, 386). These cyclone-mediated 

changes destroy or modify habitat elements (e.g., stem, branch, and leaf surfaces, undisturbed 

ground, and leaf litter) that are essential in sustaining the snails’ life-history. In addition, high 

winds and intense rains from tropical cyclones can also dislodge individual snails from leaves 
24

and branches of host plants and deposit them on the forest floor where they may be crushed by 

falling vegetation or exposed to predation by nonnative rats and snails (Hadfield 2011, pers. 

comm.).

Low Numbers of Individuals and Populations

Species that have experienced a decline in numbers and range reduction are inherently 

vulnerable to extinction from loss of habitat, predation, and localized catastrophes such as severe 

storms, diseases, climate change, or demographic stochasticity (Gilpin and Soule 1986, pp. 24–

34; Pimm et al. 1988, p. 757; Mangel and Tier 1994, p. 607). Conditions leading to this level of 

vulnerability are easily reached by island species, such as Eua zebrina, that are in small isolated 

populations. Small, isolated populations can exhibit reduced levels of genetic variability, which 

can further diminish the species’ capacity to adapt to environmental changes, thereby increasing 

the risk of inbreeding depression and reducing the probability of long-term persistence (Shaffer 

1981,p. 131; Gilpin and Soule 1986, pp. 24– 34; Pimm et al. 1988, p. 757). For Eua zebrina, 82.5 

percent of all occupied sites had fewer than 10 snails (mean occurrence = 2.2 snails per site; 

median = 2.0 snails; mode = 1 snail). The threat of small population size could seriously 

jeopardize the continued existence of Ostodes strigatus. 

Effects of Climate Change

There are no climate change studies that directly address impacts to the specific habitats of 

Ostodes strigatus. The scientific assessment completed by the Pacific Science Climate Science 

Program (Australian Bureau of Meteorology (BOM) and Commonwealth Scientific and 

Industrial and Research Organization (CSIRO). 2011, Vol. 1 and Vol. 2) provides general 

projections or trends for predicted changes in climate and associated changes in ambient 

temperature, precipitation, hurricanes, and sea level rise for countries in the western tropical 

Pacific region including Samoa (used as a proxy for American Samoa).

Although there is no specific information on the impacts of the effects of climate change to 

Ostodes strigatus, increased ambient temperature and precipitation and increased severity of 

hurricanes will likely exacerbate other threats to this species, and is likely to provide additional 

stresses on its habitat. The probability of extinction is likely to increase due to climate-change 

impacts (Intergovernmental Panel on Climate Change (IPCC) 2007, p. 48), especially given the 

restricted range of Ostodes strigatus, and small number of individuals and populations. 

Synergistic Effects

While each of the above factors negatively affect Ostodes strigatus, it is likely that synergistic 

effects of two or more factors will greatly increase the loss of populations, and contribute 

significantly to extinction. Climate change is an especially pervasive threat to the species, since 

projected increases in ambient temperature and storm severity will exacerbate other direct threats 

to O. strigatus in American Samoa. The combined effects of environmental, demographic, and 

catastrophic-event stressors, especially on small populations, can lead to a decline that is 

unrecoverable and results in extinction (Brook et al. 2008, pp. 457–458). The impacts of any one 

of the stressors described above might be sustained by a species with larger, more resilient 

populations, but in combination, habitat loss, predation, small-population risks, and climate 
25

change have the potential to rapidly affect the size, growth rate, and genetic integrity of a species 

like O. strigatus that persists as small and isolated populations. 

Conservation Efforts that Affect Viability

Invasive Plant Species Control

Several programs and partnerships to address the threat of nonnative plant species have been 

established and are ongoing in American Samoa. The National Park of American Samoa (NPSA) 

was established to preserve and protect the tropical forest and archaeological and cultural 

resources, to maintain the habitat of flying foxes, to preserve the ecological balance of the 

Samoan tropical forest, and, consistent with the preservation of these resources, to provide for 

the enjoyment of the unique resources of the Samoan tropical forest by visitors from around the 

world (Public Law 1988; Public Law 2006). Under a 50-year lease agreement between local 

villages, the American Samoa Government, and the Federal Government, approximately 8,000 

ac (3,240 ha) of forested habitat on the islands of Tutuila, Ta‘ū, and Ofu are protected and 

managed (ASG-NPSA Lease Agreement 1993).

Since 2000, the National Park of American Samoa (NPSA) has implemented an invasive plant 

management program that has focused on monitoring and removal of nonnative plant threats. 

The nonnative plant species prioritized for removal include the following: Adenanthera pavonina 

or lopa, Castilla elastica or pulu mamoe, Falcataria moluccana or tamaligi, Leucaena 

leucocephala or lusina, and Psidium cattleianum or strawberry guava (Togia 2015, in litt.). 

While none of these control efforts are targeted at habitat for Ostodes strigatus, the increasing 

awareness and removal of invasive nonnative plants may eventually been this snail.

The thrip Liothrips urichi is an insect that was introduced to American Samoa in the 1970s as a 

biocontrol for the weed Clidemia hirta (Tauili’ili and Vargo 1993, p. 59). This thrip has been 

successful at controlling Clidemia on Tutuila. Though Clidemia is still common and widespread 

throughout Tutuila, thrips inhibit its growth and vigor, preventing it from achieving ecological 

dominance (Cook 2001, p. 143).

In 2004, the American Samoa Invasive Species Team (ASIST) was established as an interagency 

team of nine local government and Federal agencies. The mission of ASIST is to reduce the rate 

of invasion and impact of invasive species in American Samoa with the goals of promoting 

education and awareness on invasive species and preventing, controlling, and eradicating 

invasive species. In 2010, the U.S. Forest Service conducted an invasive plant management 

workshop for Territorial and Federal agencies, and local partners (Nagle 2010 in litt.). More 

recently, the NPSA produced a field guide of 15 invasive plants that the park and its partners 

target for early detection and response (National Park of American Samoa 2012, in litt.). 

Predator Control

A proof of concept rat eradication project was conducted to restore habitat for the Mao 

(Gymnomyza samoensis) and other priority species by removing the predation threat of the 

Polynesian rat (R. exulans). The project was conducted on two uninhabited islands off of the 
26

eastern end of ‘Upolu, Samoa, both of which are not known to have Ostodes strigatus, and was 

intended to eradicate the Polynesian rat from both islands through aerial delivery of poison baits. 

Post-project monitoring detected rats that survived the initial eradication effort or were able to 

recolonize the island (Tye 2012, in litt.). Though this project did not affected O. strigatus

populations, it does inform ways to actively manage rats that will help future predator control 

conservation efforts.

Resiliency, Redundancy and Representation of Current Populations and the 

Species.

The island of Tutuila is the only known refuge for Ostodes strigatus, globally, and encompasses 

all of the remaining known individuals (Cowie 2001b, p. 215). Ostodes strigatus is not known to 

occur inside the National Park of American Samoa (Cowie and Cook, 1999, p. 24) on 

Tutuila. It was seen in 1993 (Miller, 1993) in locations that are not protected from clearing for 

agriculture or development. As of the last known sighting of this snail in 1993, the resilience to 

stochastic perturbations is probably very low. As the geographically defined populations on 

Tutuila represent the only known habitat for O. strigatus, redundancy and representation are also 

currently thought of as low (Table 5).

Given the status of the population, based on 1993 information from Miller (1993), and the lack 

of any sporadic recent field sightings, the overall viability of Ostodes strigatus is considered to 

be extremely low (Table 5). New surveys could greatly improve the information used to assess 

the viability of this snail.

Table 5. Current species status of Ostodes strigatus in relation to the 3 R’s.

Current Assessment of Species Viability

3 R’s1 Tutuila

Resiliency Low

Redundancy Low

Representation Low

1 3 R’s (USFWS 2016b, p 12-16)
27

Literature Cited

Abbott, R.T. 1989. Compendium of Landshells-A colorful guide to more than 2,000 of the 

world’s terrestrial shells. Madison Publishing and Associates, Inc. New York−American 

Malacologist, Inc. Melbourne, FL and Burlington, MA. First Edition. 240 pp.

[ASG-NPSA] American Samoa Government, and National Park of American Samoa. 1993. 

“Lease Agreement between Landowners of American Samoa and the American Samoa 

Government, and the Department of Interior.”

ASCC Forestry Program. 2010. “American Samoa Forestry Assessment and Resource Strategy.” 

Technical Report. Pago Pago, American Samoa: American Samoa Community College.

[ASG-NPSA] American Samoa Government (ASG) and National Park of American Samoa 

(NPSA). 1993. Lease agreement between landowners of American Samoa and the American 

Samoa Government, and the Department of Interior.

Atkinson, I.A.E. 1985. The spread of commensal species of Rattus to oceanic islands and their 

effects on island avifaunas. Pp 35-81. In Moors, P.J. (ed.), Conservation of island birds. 

Tech. Publ. No. 3, Int. Coun. Bird Preserv., Cambridge, England.

Asner, G.P. and G. Goldstein. 1997. “Correlating Stem Biomechanical Properties of Hawaiian 

Canopy Trees with Hurricane Wind Damage.” Biotropica 29 (2): 145–50.

Atkinson, C.T. and A.C. Medeiros. 2006. “Trip Report: Pilot Studies of Factors Linking 

Watershed Function and Coastal Ecosystem Health in American Samoa.” USGS 

Numbered Series 2006–1383. Open-File Report. U.S. Geological Survey. 

http://pubs.er.usgs.gov/publication/ofr20061383.

Australian Bureau of Meteorology (BOM) and Commonwealth Scientific and Industrial, and 

Research Organization (CSIRO). 2011. “Report: Climate Change in the Pacific: 

Scientific Assessment and New Research.” 

https://www.pacificclimatechangescience.org/publications/reports/report-climate-changein-the-pacific-scientific-assessment-and-new-research/.

Barker, G. 2001. “Gastropods on Land: Phylogeny, Diversity and Adaptive Morphology. I.” In 

The Biology of Terrestrial Mollusca, 1–146.

Bishop Museum. 2019. “All Specimens of Ostodes Strigatus (Gould, 1847).” 2019. 

http://pbs.bishopmuseum.org/samoasnail/specimens.asp?taxID=1966140569.

Brook, B.W., N.S. Sodhi, and C.J.A. Bradshaw. 2008. “Synergies among Extinction Drivers 

under Global Change.” Trends in Ecology & Evolution 23 (8): 453–60. 

https://doi.org/10.1016/j.tree.2008.03.011.

Clarke, B., J. Murray, and M.S. Johnson. 1984. “The Extinction of Endemic Species by a 

Program of Biological Control,” April. 

http://scholarspace.manoa.hawaii.edu/handle/10125/844.
28

Cooke, C.M. 1928. “Food Habits of Partula Zebrina Gould.” Bull. B. P. Bishop Museum, no. 47: 

5–12.

Cook, R. P. 2001. Specificity of Liothrips urichi (Thysanoptera: Phlaeothripidae) for Clidemia hirta 

in American Samoa. Proc. Hawaii Entomol. Soc. 35: 143–144.

Cowie, R.H. 1998. Catalog of the Nonmarine Snails and Slugs of the Samoan Islands. Honolulu, 

Hawaiʻi : Bishop Museum Press. https://trove.nla.gov.au/version/10067455.

Cowie, R.H. 2001a. “Can Snails Ever Be Effective and Safe Biocontrol Agents?” International 

Journal of Pest Management 47 (1): 23–40. https://doi.org/10.1080/09670870150215577.

Cowie, R.H. 2001b. “Invertebrate Invasions on Pacific Islands and the Replacement of Unique 

Native Faunas: A Synthesis of the Land and Freshwater Snails*Contribution No. 2001-

001 of Bishop Museum’s Pacific Biological Survey.” Biological Invasions 3 (2): 119–36. 

https://doi.org/10.1023/A:1014529019000.

Cowie, R.H. and R.P. Cook. 1999. “The Distribution and Abundance of Land Snails in the 

National Park of American Samoa, with Particular Focus on Partulidae.” Report. 

Cooperative National Parks Resources Studies Unit, University of Hawaii at Manoa, 

Department of Botany. http://scholarspace.manoa.hawaii.edu/handle/10125/7175.

Cowie, R.H. and R.P. Cook. 2001. “Extinction or Survival: Partulid Tree Snails in American 

Samoa.” Biodiversity & Conservation 10 (2): 143–59. 

https://doi.org/10.1023/A:1008950123126.

Craig, P, ed. 2009. Natrual History Guide to American Samoa. 3rd ed. National Park Service.

Cuddihy, L.W. and C.P. Stone. 1990. Alteration of Native Hawaiian Vegetation: Effects of 

Humans, Their Activities and Introductions. 1st Edition. edition. Honolulu, Hawaii: Univ 

of Hawaii Pr.

D’Antonio, C.M. and P.M. Vitousek. 1992. “Biological Invasions by Exotic Grasses, the 

Grass/Fire Cycle, and Global Change.” Annual Review of Ecology and Systematics 23 

(1): 63–87. https://doi.org/10.1146/annurev.es.23.110192.000431.

Department of Marine and Wildlife Resources. 2006. “A Comprehensive Strategy for Wildlife 

Conservation in American Samoa.” Technical Report. Pago Pago, American Samoa.

Eldredge, L.G. 1988. “Case Studies of the Impacts of Introduced Animal Species on Renewable 

Resources in the U.S.-Affiliated Pacific Islands.” In Topic Reviews in Insular Resource 

Development and Management in the Pacific U.S.- Affiliated Islands, edited by B.D. 

Smith, 88. Guam: Univ. Guam Marine Lab.

Elmqvist, T., W.E. Rainey, E.D. Pierson, and P.A. Cox. 1994. “Effects of Tropical Cyclones Ofa 

and Val on the Structure of a Samoan Lowland Rain Forest.” Biotropica 26 (4): 384–91. 

https://doi.org/10.2307/2389232.

Geesink, R, W.L. Wagner, and D.R. Herbst. 1999. “Fabaceae, Pea Family.” In Manual of the 

Flowering Plants of Hawai’i, edited by Warren L. Wagner, Derral R. Herbst, and S. H. 
29

Sohmer, Revised ed. edition, 629–721. Honolulu, HI: University of Hawaii Press.

Gilpin, M. and M.E. Soule. 1986. “Chapter 2: Minimum Viable Populations.” In Conservation 

Biology: The Science of Scarcity and Diversity, edited by Michael E. Soulé. Sinauer 

Associates.

Girardi, E-L. 1978. “The Samoan Land Snail Geneus Ostodes (Mollusca: Prosobranchia: 

Poteriidae).” The Veliger. 20: 191–250.

[GISD] Global Invasive Species Database. 2006. Adenanthera pavonina (plant), 

http://www.issg.org/database/species/ecology.asp?si=201&fr=1&sts=& ang=EN, accessed 

27 APR 2015.

[GISD] Global Invasive Species Database. 2008. Falcataria moluccana (plant), 

http://www.issg.org/database/species/ecology.asp?si=1249&fr=1&sts=& ang=EN,

accessed 16 JUN 2015.

[GISD] Global Invasive Species Database. 2010. Spathodea campanulata (plant), 

http://www.issg.org/database/species/ecology.asp?si=75&fr=1&sts=& ang=EN, accessed 

27 APR 2015.

Goldin, M.R. 2002. Field Guide to the Samoan Archipelago: Fish, Wildlife and Protected Areas. 

Honolulu, Hawaii: Bess Press.

Hadfield, M.G., S.E. Miller, and A.H. Carwile. 1993. “The Decimation of Endemic Hawai’ian 

Tree Snails by Alien Predators.” American Zoologist 33 (6): 610–22. 

https://doi.org/10.2307/3883724.

Hadfield, M.G. and B.S. Mountain. 1980. “A Field Study of a Vanishing Species, Achatinella 

Mustelina (Gastropoda, Pulmonata), in the Waianae Mountains of Oahu,” October. 

http://scholarspace.manoa.hawaii.edu/handle/10125/1633.

Hadfield, M.G. and J.E. Saufler. 2009. “The Demographics of Destruction: Isolated Populations 

of Arboreal Snails and Sustained Predation by Rats on the Island of Moloka’i 1982–

2006.” Biological Invasions 11 (7): 1595–1609. https://doi.org/10.1007/s10530-008-

9409-9.

Hadfield, M.G. 2005, in litt. A survey of the Partulina tree snails on Lanai, report submitted to 

D. Stokes, Castle & Cooke Resorts, Lanai City, Hawaii, 28 MAY 2005, 8 pp. 

Hadfield, M.G. 2006, in litt. Memo regarding survey for Newcombia cumingi, October 20-22, 

2006, 4 pp. 

Hadfield, M.G. 2011, pers. comm. Personal communication from Dr. Mike Hadfield to FWS 

Biologist Carrie Harrington providing information on threats to Hawaiian tree snails, 

February 7, 2011. 

Harrington, R.A., J.H. Fownes, P.G. Scowcroft, and C.S. Vann. 1997. “Impact of Hurricane Iniki 

on Native Hawaiian Acacia Koa Forests: Damage and Two-Year Recovery.” Journal of 

Tropical Ecology 13: 539–58. https://doi.org/10.1017/S0266467400010701.

Hobdy, R. 1993. “Lana’i-A Case Study: The Loss of Biodiversity on a Small Hawaiian Island.” 
30

Pacfic Science 47 (3): 201–10.

Hopper, D.R. and B.D. Smith. 1992. “Status of Tree Snails (Gastropoda: Partulidae) on Guam, 

with a Resurvey of Sites Studied by H. E. Campton in 1920,” January. 

http://scholarspace.manoa.hawaii.edu/handle/10125/1675.

Howarth, F.G. 1983. “Classical Biocontrol: Panacea or Pandora’s Box.” 

http://scholarspace.manoa.hawaii.edu/handle/10125/11156.

Howarth, F.G. 1985. “Impacts of Alien Land Arthropods and Mollusks on Native Plants and 

Animals in Hawaii.” In Hawaii’s Terrestrial Ecosystems: Preservation and 

Management., edited by C.P. Stone and J.M. Scott, 149–79. Honolulu, Hawaii: 

Cooperative National Park Research Studies Unit,.

Howarth, F.G. 1991. “Environmental Impacts of Classical Biological Control.” Annual Review of 

Entomology 36 (1): 485–509. https://doi.org/10.1146/annurev.en.36.010191.002413.

Intergovernmental Panel on Climate Change (IPCC). “AR4 Climate Change 2007: Impacts, 

Adaptation, and Vulnerability.” IPCC, 2007. https://www.ipcc.ch/report/ar4/wg2/.

Integrated Taxonomic Information System (ITIS). 2019. “ITIS Standard Report Page: Ostodes.” 

2019. 

https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=331

422#null.

Knapp, K.R., M.C. Kruk, D.H. Levinson, H.J. Diamond, and C.J. Neumann. 2010. “The 

International Best Track Archive for Climate Stewardship (IBTrACS).” Bulletin of the 

American Meteorological Society 91 (3): 363–76. 

https://doi.org/10.1175/2009BAMS2755.1.

Levin, M. J. and P. A. Wright. 1974. “Report on the 1974 Census of American Samoa: Part II.” 

Honolulu, Hawaii: University of Hawaii at Manoa, East_West Population Institute. 

http://pacificweb.org/categories/Statistical%20Activities/Census/AmericanSamoaCensus.

html.

Lugo, A. E. 2008. “Visible and Invisible Effects of Hurricanes on Forest Ecosystems: An 

International Review.” Austral Ecology 33 (4): 368–98. https://doi.org/10.1111/j.1442-

9993.2008.01894.x.

Mangel, M. and C. Tier. 1994. “Four Facts Every Conservation Biologists Should Know about 

Persistence.” Ecology 75 (3): 607–14. https://doi.org/10.2307/1941719.

Matson, P. 1990. “Plant-Soil Interactions in Primary Succession at Hawaii Volcanoes National 

Park.” Oecologia 85 (2): 241–46. https://doi.org/10.1007/BF00319408.

Meyer, R., J. Seamon, S. Fa’aumu, and I. Lalogafuafua. 2017. “Classification and Mapping of 

Wildlife Habitat in American Samoa: An Object-Based Approach Using High Resolution 

Orthoimagery and LIDAR Remote Sensing Data.” Technical Report 1. American Samoa: 

Department of Marine and Wildlife Resources.
31

Miles, A. 2015c, in litt. Email from DMWR wildlife biologist Adam Miles to FWS biologist 

James Kwon providing information on the status of Eua zebrina and Ostodes strigatus in 

American Samoa, 11 FEB 2015. 

Miller, S.E. 1993. “Final Report on Surveys of the Arboreal and Terrestrial Snail Fauna of 

American Samoa.” Honolulu, Hawaii: Pacrific Biomedical Research Center. 

http://webcache.googleusercontent.com/search?q=cache:rrdSq7H5SXsJ:irmaservices.nps.

gov/datastore/v4/rest/DownloadFile/148783%3FaccessType%3DDOWNLOAD+&cd=1

&hl=en&ct=clnk&gl=us&client=firefox-b-1-d.

Ministry of Natural Resources & Environment (MNRE). 2014. “In Litt. Table 1: Samoa Land 

Cover by Island 2014.” http://www.sbs.gov.ws/index.php/new-documentlibrary?view=download&fileId=1749.

Mueller-Dombois, D. and F.R. Fosberg. 1998. Vegetation of the Tropical Pacific Islands. 

Ecological Studies. New York, NY: Springer New York. https://doi.org/10.1007/978-1-

4419-8686-3.

Murray, J., M.S. Johnson, and B. Clarke. 1982. “Microhabitat Differences Among Genetically 

Similar Species of Partula.” Evolution 36 (2): 316–25. https://doi.org/10.1111/j.1558-

5646.1982.tb05047.x.

Nagle, B. 2010, in litt. Invasive plant project management, training workshop report. 27 pp. 

National Park of American Samoa. 2012, in litt. Invasive plant field guide. 32 pp.

NOAA IBTrACS. 2019. “IBTrACS - International Best Track Archive for Climate 

Stewardship.” 2019. https://www.ncdc.noaa.gov/ibtracs/.

Ohbayashi, T., I. Okochi, H. Sato, T. Ono, and S. Chiba. 2007. “Rapid Decline of Endemic 

Snails in the Ogasawara Islands, Western Pacific Ocean.” Applied Entomology and 

Zoology 42 (3): 479–85. https://doi.org/10.1303/aez.2007.479.

Pacific Climate Change Science Program (PCCSP). 2019. “American Samoa | Pacific Climate 

Change Portal.” 2019. https://www.pacificclimatechange.net/country/american-samoa.

Pacific Ecosystems At Risk (PIER). 2016. “Spathodea Campanulata: Info from PIER (PIER 

Species Info).” 2016. http://www.hear.org/pier/species/spathodea_campanulata.htm.

Pearsall, S.H. and W.A. Whistler. 1991. Terrestrial ecosystem mapping for Western Samoa: 

summary, project report, and proposed national parks and reserves plan. Prepared for the 

Government of Western Samoa by the South Pacific Regional Environment Program. 80 pp. 

Pereira, J.M. 1981. A coastal zone management atlas of American Samoa. 1981. Development 

Planning Office, American Samoa Government. Statistical Tables (p.68), Land use trends by

planning district.

Pimm, S.L., H. L. Jones, and J. Diamond. 1988. “On the Risk of Extinction.” The American 

Naturalist 132 (6): 757–85.

Public Law. 1988. An Act to Establish the National Park of American Samoa.
32

Public Law. 2006. Boundary Adjustment of the National Park of American Samoa. 100-336.

Samoa Bureau of Statistics (SBS). 2011. “Population and Housing Census 2011 Analytical 

Report.” Census. Apia Samoa: Samoa Bureau of Statistics.

Shaffer, M.L. 1981. “Minimum Population Sizes for Species Conservation.” BioScience 31 (2): 

131–34. https://doi.org/10.2307/1308256.

Smith, C.W., C.P. Stone, and J.M. Scott. 1985. “Impact of Alien Plants on Hawaii’s Native 

Biota.” In Hawaii’s Terrestrial Ecosystems: Preservation and Management, 180–250. 

University of Hawaii: Cooperative National Park Resources Studies Unit.

Smith, C.W. 1989. Non-native plants. In Conservation Biology in Hawaii, Stone, C.P., D.B. 

Stone, LW. Cuddihy, and M.E. Land (eds.), University of Hawaii Press, Honolulu. Pp. 60–

69.

Solem, A. 1975. Final report, Office of Endangered Species. Contract No. 14·16-0008·837

Space, J.C. and T. Flynn. 2000. “Observations on Invasive Plant Species in American Samoa.” 

Invasive plant species survey: Technical Report. Pacific Islands Committee, Council of 

Western State Foresters.

Space, J.C. and T. Flynn. 2002. “Report to the Government of Samoa on Invasive Plant Species 

of Environmental Concern | Pacific Invasive Learning Network.” Technical Report. 

Honolulu, Hawaii: U.S.D.A. Forest Service, Pacific Southwest Research Station, Institute 

of Pacific Islands Forestry,. https://piln.sprep.org/content/74287.

Stein, S.M., M.A. Carr, G.C. Liknes, and S.J. Comas. 2014. “Islands on the Edge: Housing 

Development and Other Threats to America’s Pacific and Caribbean Island Forests: A 

Forests on the Edge Report.” Gen. Tech. Rep. NRS-137. Newtown Square, PA: U.S. 

Department of Agriculture, Forest Service, Northern Research Station. 55 p. 137: 1–55. 

https://doi.org/10.2737/NRS-GTR-137.

Sugiura, S. 2010. “Prey Preference and Gregarious Attacks by the Invasive Flatworm 

Platydemus Manokwari.” Biological Invasions 12 (6): 1499–1507. 

https://doi.org/10.1007/s10530-009-9562-9.

Sugiura, S. and Y. Yamaura. 2010. “Potential Impacts of the Invasive Flatworm Platydemus 

Manokwari on Arboreal Snails.” In Restoring the Oceanic Island Ecosystem: Impact and 

Management of Invasive Alien Species in the Bonin Islands, edited by Kazuto Kawakami 

and Isamu Okochi, 45–50. Tokyo: Springer Japan. https://doi.org/10.1007/978-4-431-

53859-2_7.

Tauili’ili, P. and A. M. Vargo. 1993. “History of Biological Control in American Samoa.” 

Micronesica (USA). http://agris.fao.org/agris-search/search.do?recordID=US9426608.

Thornbery-Ehrlich, T. 2008. “National Park of American Samoa Geologic Resource Evaluation 

Report.” 2008/025. Natural Resources Report NPS/NRPC/GRD/NRR. Denver, Colorado.
33

Togia, T. 2015, in litt. Email from Tavita Togia, NPSA terrestrial ecologist, to James Kwon, U.S. 

Fish and Wildlife Service, regarding nonnative plant and feral pig control, dated 24 APR 

2015.

Tye, A. 2012, in litt. Restoration of Nuutele and Nuulua Islands (Aleipata Group), Samoa 

through the management of introduced rats and ants. CEPF final project completion 

report for Secretariat of the Pacific Regional Environment Programme (SPREP). 33 pp. 

Unkown. 1956. “Census of American Samoa: 1930-1956.” Census. 

http://pacificweb.org/categories/Statistical%20Activities/Census/AmericanSamoaCensus.

html.

U. S. Census Bureau. 1982. “Chapter A: Number of Inhabitants. Volume 1: Characteristics of the 

Population. 1980 Census of Population, Part 56: American Samoa.” Census. U.S. Census 

Bureau, Economics and Statistical Administration, U.S. Department of Commerce. 

http://pacificweb.org/categories/Statistical%20Activities/Census/AmericanSamoaCensus.

html.

U. S. Census Bureau. 1992. “Social Economic, and Housing Characteristics: American Samoa. 

1990 Census of Population and Housing.” Census. U.S. Census Bureau, Economics and 

Statistical Administration, U.S. Department of Commerce. 

http://pacificweb.org/categories/Statistical%20Activities/Census/AmericanSamoaCensus.

html.

U. S. Census Bureau. 2010. “Census 2000 and 2010 for American Samoa [Data File].” 2010. 

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKE

wjynsCqj8LjAhWmTN8KHTlxAmIQFjAAegQIBBAC&url=https%3A%2F%2Fwww.ce

nsus.gov%2F2010census%2Fnews%2Fxls%2Fcb11cn177_as.xls&usg=AOvVaw28FqcL

YgSuUELROmbr5BGH.

U.S. Census Bureau. 2011, in litt. American Samoa population count. 

https://www.census.gov/2010census/news/releases/operations/cb11-cn177.html, accessed 

on 09 SEP 2015. 

[USDA] U.S. Department of Agriculture-Agricultural Research Service. National Genetic 

Resources Program. 2006. Germplasm Resources Information Network – (GRIN) [Online 

Database]. National Germplasm Resources Laboratory, Beltsville Maryland, 

http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?70913, accessed on 13 JUL 2015.

[USFWS] U.S. Fish and Wildlife Service. 2016a. Endangered and threatened wildlife and 

plants; endangered status for five species from American Samoa; Final Rule. Federal 

Register 81:65466-65508.

[USFWS] U.S. Fish and Wildlife Service. 2016b. USFWS Species Status Assessment 

Framework: an integrated analytical framework for conservation. Version 3.4. Dated August 

2016.

Vaught, K.C. 1989. A Classification of the Living Mollusca. 1st ed. Melbourne, Fla. : American 

Malacologists,.
34

Vitousek, P.M., C.M. D’Antonio, L.L. Loope, M. Rejmánek, and R. Westbrooks. 1997. 

“Introduced Species: A Significant Component of Human-Caused Global Change.” N. Z. 

J. Ecol. 21 (1): 1–16.

Wagner, W., D.R. Herbst, and R.S.N. Yee. 1985. “Status of the Native Flowering Plants of the 

Hawaiian Islands.” In Hawai‘i’s Terrestrial Ecosystems: Preservation and Management, 

edited by C.P. Stone and J.M. Scott. Honolulu, Hawaii: Univ. Hawai‘i Coop. Natl. Park 

Resources Stud. Unit. Univ. Hawai‘i Press.

Whistler, W.A. 1992. “Botanical Inventory of the Proposed Ta’u Unit of the National Park of 

American Samoa.” Report. Cooperative National Park Resources Studies Unit, 

University of Hawaii at Manoa, Department of Botany. 

http://scholarspace.manoa.hawaii.edu/handle/10125/7120.

Whistler, W.A. 1994. “Botanical Inventory of the Proposed Tutuila and Ofu Units of the 

National Park of American Samoa.” Report. Cooperative National Park Resources 

Studies Unit, University of Hawaii at Manoa, Department of Botany. 

http://scholarspace.manoa.hawaii.edu/handle/10125/7240.

Whistler, W.A. 2002. The Samoan Rainforest: A Guide to the Vegetation of the Samoan 

Archipelago. Isle Botanica.