Pygmy Rabbit Surveys on State Lands in Oregon 

By Joan Hagar, George Lienkaemper 

Open-File Report 2007-1015 


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 

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Hagar, J., Lienkaemper, G. 2007, Pygmy rabbit surveys on state lands in Oregon, U.S. Geological Survey 

Open-File Report 2007-1015, 23p.

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Contents

Contents ..............................................................................................................................................................................iii

Introduction .........................................................................................................................................................................1

Methods ...............................................................................................................................................................................1

Habitat Model..................................................................................................................................................................1

Rabbit Surveys ................................................................................................................................................................3

Habitat Descriptions.......................................................................................................................................................4

Results ..................................................................................................................................................................................4

Discussion............................................................................................................................................................................6

References Cited ................................................................................................................................................................7

Appendix ..............................................................................................................................................................................9

Tables 

1. Summary of results of survey for Pygmy Rabbits in Deschutes, Harney, Lake, and Malheur counties, 

Oregon. ...................................................................................................................................................................5 

2. Comparison of mean and 95% confidence intervals for shrub characteristics among active and inactive 

pygmy rabbit sites, and unoccupied sites........................................................................................................5 

3. Comparison of average clay and sand content of soil among active and inactive pygmy rabbit sites, and 

unoccupied sites...................................................................................................................................................5 

Figures 

 1. Location of pygmy rabbit surveys in southeast Oregon, 2004 – 2005.................................................................2

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Conversion Factors 

Multiply By To obtain 

inch (in.) 2.54 centimeter (cm) 

foot (ft) 0.3048 meter (m) 

mile (mi) 1.609 kilometer (km) 

acre 0.4047 hectare (ha)

iv
Pygmy Rabbit Surveys on State Lands in 

Oregon Final Report 

By Joan Hagar, George Lienkaemper 

Introduction 

The pygmy rabbit (Brachylagus idahoensis) is classified by the federal government as a 

species of concern (i.e., under review by the U.S. Fish and Wildlife Service for consideration as a 

candidate for listing as threatened or endangered under the Endangered Species Act) because of 

its specialized habitat requirements and evidence of declining populations. The Oregon 

Department of Fish and Wildlife (ODFW) lists pygmy rabbits as “sensitive-vulnerable,” meaning 

that protective measures are needed if sustainable populations are to be maintained over time 

(Oregon Natural Heritage Program, 2001). The Oregon Natural Heritage Program considers this 

species to be threatened with extirpation from Oregon. Pygmy rabbits also are a species of 

concern in all the other states where they occur (NatureServe, 2004). The Washington population, 

known as the Columbia Basin pygmy rabbit, was listed as endangered by the federal government 

in 2003. 

Historically, pygmy rabbits have been collected from Deschutes, Klamath, Crook, Lake, 

Grant, Harney, Baker, and Malheur Counties in Oregon. However, the geographic range of pygmy 

rabbit in Oregon may have decreased in historic times (Verts and Carraway, 1998), and 

boundaries of the current distribution are not known. Not all potentially suitable sites appear to be 

occupied, and populations are susceptible to rapid declines and local extirpation (Weiss and Verts, 

1984). In order to protect and manage remaining populations on State of Oregon lands, Oregon 

Department of Fish and Wildlife needs to identify areas currently occupied by pygmy rabbits, as 

well as suitable habitats. 

The main objective of this survey was document to presence or absence of pygmy rabbits 

on state lands in Malheur, Harney, Lake, and Deschutes counties. Knowledge of the location and 

extent of pygmy rabbit populations can provide a foundation for the conservation and 

management of this species in Oregon. The pygmy rabbit is just one of a suite of species of 

concern associated with sagebrush habitats in the Great Basin. Because information on habitat and 

distribution of many species is scarce, a secondary goal of the rabbit surveys was to list all other 

vertebrate species encountered on surveyed sites. This information may be useful in directing 

future studies aimed at specific taxa. 

Methods 

Habitat Model 

The priority survey area comprised state lands within the known historic range of suitable 

habitat for pygmy rabbits, in Malheur, Harney, Lake, and Deschutes Counties (Fig. 1). In order to 

prioritize areas to survey within the large blocks of state land in this landscape, we developed a 
model to categorize potential habitat suitability for pygmy rabbits according to soil and vegetation 

characteristics. We also used reconnaissance from the air to identify potential habitat in large state

land blocks (see “Rabbit Surveys”, next page). 

Figure 1. Location of pygmy rabbit surveys in southeast Oregon, 2004 – 2005.

Our model was modified from a similar model developed by Rachelow and Svancara 

(2003). Areas with tree cover, without sage, or with soils less than 61cm deep were eliminated 

from consideration as potential habitat. Because detailed soil data (SSURGO; USDA-NRCS 

2005) were not available for the entire study area, we used the statewide (STATSGO; USDA-SCS 

1994) soil information in our analysis, recognizing that it is coarser than other detailed soil data. 

Information about clay content of soils was not available for this data set, so this parameter was 

not included in the model. In addition, vegetation types were not part of the STATSGO data set, 

and a sagebrush geographic information system (GIS) layer was used as a surrogate.

2
The habitat-potential layer was produced by multiplying scores for each layer in order to 

clearly differentiate areas of high potential. Based on the primary importance of sagebrush cover 

to pygmy rabbits, areas with Wyoming big sage were assigned a score of 1 (highest suitability), 

areas with mountain big sage and mountain low sage were assigned 2, and all other sage types a 3 

(lowest suitability). Sage-cover type was determined from the sagebrush layer of “sagestitch” 

(USGS, 2005). Pygmy rabbits are typically associated with flat topography (Gabler and others, 

2000; Rachlow and Svancara, 2003). Therefore, areas with less than 8o slope were assigned a 

score of 1, those with 8 to 20o slope were assigned a 2, and steeper areas were assigned a 3. Slope 

steepness was determined from SRTM elevation data. 

Rabbit Surveys 

We overlaid our model of habitat potential on a map of current (2004) state land 

ownership boundaries in eastern Oregon, obtained from the Division of State Lands. State land 

blocks that encompassed areas of at least 1⁄4 section (32.38 ha) predicted by our model as having 

very high or high rabbit habitat potential (red and yellow on habitat potential maps) were 

prioritized for ground surveys. In addition, C. Carey (ODFW Biologist) identified potential habitat 

from aerial transects flown over large blocks of state land in southeast Lake County, near 

Wagontire in Harney Coungy, and southeast of New Princeton in Harney and Malheur counties. 

Universal transverse mercator (UTM) coordinates of suitable patches of tall sage identified from 

the air as potential habitat were recorded with a global-positioning-system (GPS) unit to facilitate

relocation during ground surveys. 

 Once priority survey sites were identified, we made field visits to all areas predicted as

having high or very high rabbit-habitat potential and most areas identified by aerial 

reconnaissance to determine the presence or absence of rabbits (157 sites ground surveyed). We 

did not visit approximately 25 of the sites identified from aerial reconnaissance in the large block 

of state land southeast of New Princeton because our model predicted low habitat potential and 

the access was very difficult (roadless or required traversing private land). Eleven of the 157 sites 

were on private land, and were unintentionally surveyed because aerial reconnaissance identified 

potential habitat adjacent to state lands and boundaries were not clearly marked on the ground. 

At each site visited, two observers walked transects spaced no more than .40 km apart 

through at least 75% of the area of potential habitat, looking for patches that were likely to 

support centers of pygmy rabbit activity. Because pygmy rabbits and their sign (pellets, burrows) 

can be detected at any time of day and during any time of year, we did not temporally restrict 

surveys. Each site was visited one time to determine presence or absence. 

We checked patches of tall, dense big sage thoroughly for pygmy rabbits and their 

burrows, pellets, and tracks. We classified sites according to use status of any burrows that were 

located (e.g., currently used, apparently unused, or collapsed), and presence and age of pellets. 

Presence of fresh pellets, open burrows, or sighting of pygmy rabbits provided evidence for 

classifying a site as “active” (occupied by pygmy rabbits at the time of the survey). We classified 

sites as inactive if old pellets or collapsed burrows were found in suitable habitat. An inactive 

classification indicated that pygmy rabbits had used the site but were no longer present. Sites 

without evidence of occupancy by pygmy rabbits (no pellets, no burrows) were classified as “no 

rabbits.” 

The legal and UTM coordinates of all survey routes and burrows were recorded using a 

GPS unit. Areas that were surveyed but did not have sign of pygmy rabbits also were described 

along with location data. Surveys were conducted from September 2004 to November 2005. 

3
Habitat Descriptions 

We used a line-point intercept method (Elzinga and others 2001) to describe shrub cover 

in 10 x 10-m plots centered on burrows at nine sites occupied by pygmy rabbits and three inactive 

sites. We did not collect habitat data at active rabbit sites on private land. We sampled vegetation 

on five parallel 10-m long transects spaced at 2.5 m intervals. We dropped a pin flag every 50 cm 

along each transect and recorded the species of shrub intercepted in the canopy, and whether 

grass, forbs, or litter were intercepted below the shrub canopy. At three sites where no rabbit sign

was detected, we randomly centered vegetation-sampling plots. Average shrub cover and height 

was compared among the three categories of burrow status using ANOVA with a least square 

means multiple comparison procedure. 

We collected soil samples from burrows at 10 occupied sites, 3 inactive sites, and 5 

unoccupied sites. Soil samples were classified by texture (USDAA textural class) and analyzed 

for sand and clay content at the Soil Physical Characterization Lab at Oregon State University. 

Results 

Of the 262,725 ha of state lands in eastern Oregon (Fig. 1), 181,438 ha were unsuitable as 

pygmy rabbit habitat based on vegetation type (i.e., not sage). Of the remaining area, 76,890 ha 

(29% of total state land area) were classified as high-to-medium habitat potential by our model, 

and 4,397 ha (2%) were classified as low potential. 

Only 11% of the 157 sites surveyed had evidence of occupancy by pygmy rabbits at the 

time of the survey, and an additional 9% had evidence that pygmy rabbits had used the site 

previously but were no longer present (Table 1). All active sites and most inactive sites were 

located in Harney and Lake counties; only one inactive site was in Malheur County. Maps of sites 

surveyed overlain on habitat potential as predicted by our model are in Appendix A. 

Rabbit-occupancy status was correlated with variation in shrub cover and height. Active 

sites had greater average shrub cover than inactive or unoccupied sites (Table 2). Furthermore, the 

maximum cover at inactive sites barely overlapped the minimum at active sites. Unoccupied sites 

had notably low cover of shrubs. Shrub cover of 20-40% is considered marginal habitat for pygmy 

rabbits (Green and Flinders 1980, Katzner and Parker 1997). More than 40% cover provides 

suitable habitat. We sampled vegetation at very few unoccupied sites because it was obvious that 

shrub cover was well below that required to be suitable habitat for pygmy rabbits (i.e., less than 

20%) at the vast majority of sites. A coarser method of describing vegetation, such as 

characterizing cover classes from remote sensing data, would be a more efficient and cost 

effective means than line-point intercepts for characterizing differences in cover between 

occupied and unoccupied sites. 

Shrub height also is an important habitat feature for pygmy rabbits, and is positively 

associated with habitat suitability. Average shrub heights reported for occupied sites and burrow 

locations are typically greater than 65 cm (Green and Flinders, 1980; Weiss and Verts, 1984). The 

shrub heights we observed for both active and inactive sites were therefore consistent with 

suitable habitat reported from other studies (Table 2). 

Because pygmy rabbits dig their own burrows, soil texture and content is very important. 

Suitable soils have greater sand and less clay (usually less than 18%; Gabler, 1997; Rachlow and 

Svancara, 2003). These proportions of sand and clay seem to provide the optimum balance 

between ease of burrow excavation and resistance to collapse. The soil composition we observed 

at active and previously occupied sites was close to what would be expected for suitable habitat. 

Soil composition was similar across all sites (Table 3). Similarly, we found no obvious difference 

in soil textural classification among sites of different occupancy status. Soils at active rabbit sites 

4
fell into four textural classes: sandy loam (six sites), silt loam (two sites), loam (one site), and 

loamy sand (one site). Inactive sites were classified as sandy loam (one site) and loam (two sites). 

Unoccupied sites were classified as sandy loam (three sites), silt loam (one site), and loam (one 

site). 

Table 1. Summary of results of survey for Pygmy Rabbits in Deschutes, Harney, Lake, and 

Malheur counties, Oregon. Active rabbit sites had evidence of occupancy by pygmy rabbits at the 

time of the survey; Inactive sites had evidence that pygmy rabbits had used the site but were no 

longer present; No rabbit sites had no evidence of occupancy by pygmy rabbits. 

Ownership # Sites Surveyed Active Rabbits Inactive No Rabbits 

State 143 9 13 121 

BLM 3 1 0 2 

Private 11 8 1 2 

 Totals 157 18 14 125 

Table 2. Comparison of mean and 95% confidence intervals for shrub characteristics among 

active and inactive pygmy rabbit sites, and unoccupied sites. Means with different letters are 

significantly different (P < 0.10, ANOVA). 

Shrub Cover (%) Shrub Height (cm) 

Status N Mean 95% CI N Mean 95% CI 

Active 9 57 A 50.6 62.8 8 86 A 69.8 103.0 

Inactive 3 40 B 29.8 50.8 3 76 AB 49.1 103.3 

No rabbits 3 34 B 23.5 44.5 3 58 B 30.5 84.7 

5
Table 3. Comparison of average clay and sand content of soil among active and inactive pygmy 

rabbit sites, and unoccupied sites.

Status N Clay (%) Sand (%) 

Active 10 12 58 

Inactive 3 12 52 

No rabbits 5 9 53 

Discussion 

The most important factors influencing habitat suitability for pygmy rabbits include 

vegetation composition (i.e., sage), shrub cover, shrub height, and soil characteristics. The status 

of pygmy rabbit occupancy on the sites we surveyed did not vary with vegetation composition or 

soil characteristics because all sites surveyed were dominated by big sage, and soil characteristics 

were similar across sites. The variables that seemed to best account for differences in occupancy 

status among sites were shrub cover and height. All of the sites we surveyed had evidence of 

cattle grazing, and in many areas it was evident that heavy use by cattle had resulted in a decrease 

of shrub cover. In addition to reducing shrub cover through trampling, grazing by cattle also has 

been reported to reduce the nutritional quality of forage for pygmy rabbits (Thines and others, 

2004). Thus, many of the sites where we found no evidence of pygmy rabbit occupancy may have 

had the potential to support pygmy rabbits, as predicted by our model, but habitat may have been 

rendered unsuitable due to insufficient shrub cover as a result of heavy grazing. 

In addition to the patch-level habitat characteristics investigated in this survey, factors

operating at larger spatial scales also likely have an important influence on site occupancy by 

pygmy rabbits. Although pygmy rabbits are apparently capable of dispersing among patches of 

appropriate habitat in landscapes patterned by natural processes (Katzner and Parker, 1998), 

increasing fragmentation of sagebrush cover from anthropogenic sources may limit successful

dispersal (Weiss and Verts, 1984). Thus, localized populations of pygmy rabbits that become 

isolated by habitat fragmentation may become extinct, and potentially suitable habitat patches 

may remain unoccupied if they are too small or too distant from source habitats. Little information 

is currently available to assess effects of fragmentation on pygmy rabbit habitat use and 

population dynamics. Future research to investigate the influence of landscape level habitat 

patterns on patch occupancy by pygmy rabbits would help fill this information void. Using 

location data from this and other surveys, GIS models could identify thresholds of minimum patch 

size that currently support pygmy rabbit populations. Combining this approach with information 

from current investigations of dispersal distances (e.g., T. Forbes’ work), maximum inter-patch 

distances also could be estimated. In addition, genetic analysis could be used to evaluate effects of 

fragmentation on diversity and variation of genetic material among metapopulations. 

6
References Cited 

Buol, S.W., Southard, R.J., Graham, R.C., and McDaniel, P.A., 2003, Soil genesis and 

classification, Fifth edition, Iowa State Press, Ames, USA. 

Comer, P., Kagan, J., Heiner, M., and Tobalske, C., 2002, Current distribution of sagebrush and 

associated vegetation in the western United States (excluding New Mexico and Arizona), 

Interagency Sagebrush Working Group. 

Elzinga, C.L., Salzer, D.W., Willoughby, J.W., and Gibbs, J.P., 2001, Monitoring plant and 

animal populations, Blackwell Publishing, Malden, Mass. 

Gabler, K.I., 1997, Distribution and habitat requirements of the pygmy rabbit (Brachylagus 

idahoensis) on the Idaho National Engineering and Environmental Laboratory, M.S. thesis, 

Idaho State University, Boise, Idaho. 

Gabler, K.I., Laundre, J.W., and Heady L.T., 2000, Predicting the suitability of habitat in 

southeast Idaho for pygmy rabbits, J. Wildl. Manage., v. 64(3), p. 759-764. 

Green, J.S., and Flinders, J.T., 1980, Habitat and dietary relationships of the pygmy rabbit, J. 

Range Manage., v. 33, p. 136-142. 

Katzner, T.E., and Parker, K.L., 1997, Vegetative characteristics and size of home ranges used by 

pygmy rabbits (Brachylagus idahoensis) during winter, J. Mammal., v 78 p. 1063-1072. 

Katzner, T.E., and Parker, K.L., 1998. Long-distance movements from established burrow sites by 

pygmy rabbits (Brachylagus idahoensis) in southwestern Wyoming, Northwestern Naturalist v. 

7, p. 72-74. 

NatureServe, 2004, NatureServe Explorer: An online encyclopedia of life [web application], 

Version 3.1, NatureServe, Arlington, Virg., Available http://www.natureserve.org/explorer, 

Accessed May 18, 2004. 

Oregon Natural Heritage Program, 2001, Rare, Threatened and Endangered Species of Oregon, 

Oregon Natural Heritage Program, Portland, Oreg. 

Rachlow, J., and Svancara, L., 2003, Pygmy rabbit habitat in Idaho, University of Idaho, Moscow, 

Idaho, Unpublished report. 

Thines, N.J.S., Shipley, L.A., and Sayler, R.D., 2004, Effects of cattle grazing on ecology and 

habitat of Columbia Basin pygmy rabbits (Brachylagus idahoensi, Biological Conservation, v. 

119, p. 525-534. 

Ulmschneider, H., Hays, D., Roberts, H., Rachlow, J., Forbes, T., Himes, J., Sequin, E., Haworth, 

M., Katzner, T., Kozlowski, A., Rauscher, R., Lauridson, P., 2004, Surveying for pygmy rabbits 

(fourth draft), U.S. Department of the Interior, Bureau of Land Management, Owyhee Field 

Office, Boise, Idaho. 

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USDA-SCS (U.S. Department of Agriculture, Soil Conservation Service), 1994, State Soil 

Geographic (STATSGO) data base for Oregon, U.S. Department of Agriculture, Soil 

Conservation Service, Fort Worth, Texas. 

USGS, Forest and Rangeland Ecosystem Science Center, Snake River Field Station, 2005, 

Current distribution of sagebrush and associated vegetation in the Columbia Basin and 

Southwestern Regions, U.S. Geological Survey, Corvallis, Oreg. 

Verts, B.J., and Carraway, L.N., 1998, Land mammals of Oregon, University of California Press, 

Berkeley, p. 128-131. 

Weiss, N.T., and Verts, B.J., 1984, Habitat and distribution of pygmy rabbits (Sylvilagus 

idahoensis) in Oregon, Great Basin Naturalist v. 44, p. 563-571. 

Welch, B.L., 2005, Big sagebrush: A sea fragmented into lakes, ponds, and puddles, U.S. 

Department of Agriculture, Forest Service, Rocky Mountain Research Station, General 

Technical Report RMRS-GTR-144, Fort Collins, Colo. 

8
Appendix 

Pygmy Rabbit habitat potential and locations of rabbit surveys in Deschutes, Harney, Lake, and 

Malheur Counties, Oregon 2004 – 2005. Master figure below indicates the page number in 

Appendix A where each map is displayed. The numbers shown on the figure below correspond 

with page numbers as follows: 

9

1

2

3

4

5

6

7

8

9


!

43°0'0" 

! Tucke Place ") 

! ! !

Miller Place ! ") 

!

42°48'0" !

P

ygm

y Rabbit

Habitat P

otential

ST

A

T

S

G

O M

o

d

el

Near S

ageview, Oregon

Rabbit Surveys 2004-2005

! Active burrow ! Inactive burrow 

! No rabbit sign

Roads

State highwaySecondary roadFour-wheel driveUS highway

State Administered LandPygmy Rabbit Potential Habitat

HighLow 

6 3 0 

Kilometers 

Sageview ") 

O R

E G O

N 1 Survey

Locations 

-119°36'0" -119°24'0" -119°12'0" Analysis and cartography by George Lienkaemper, USGS FRESC 

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10

11

12

13

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