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Columbia Basin Pygmy Rabbit Vet Advisor Report 2010

SSP/TAG:      Columbia Basin Pygmy Rabbit (Brachylagus idahoensis)

DATE: Feb 2010



Name:            Lisa Harrenstien     e-mail:


Address:        Oregon Zoo, 4001 SW Canyon Rd., Portland, OR 97221                  


Phone: (day) 503-525-4230 (evening) 503-236-6812 (FAX) 503-220-2797


MORBIDITY (Significant illnesses/issues facing this species this year):

·      Bacterial typhlitis/colitis (with coliforms or with clostridia)

·      Coccidiosis, especially in juveniles up to 3 months old but occasionally in adults as well.

·      Coronaviral enteritis

All of the above have resulted in peracute mortality. Rarely is a rabbit clinically ill for any length of time.




MORTALITY (Causes of death in this year):

Cause of Death                                                       SB #               Sex                 Age


See additional spreadsheet file including the past 2 years of Oregon Zoo’s mortalities, as an example. Oregon Zoo’s population is approximately 1/3 of the total captive population. 2 other facilities maintain pygmy rabbits in captive propagation facilities, Washington State University (lab animal dept – 60% of the overall population) and Northwest Trek (10% of the overall population). Their mortality records are more difficult to obtain, but a second summary spreadsheet is included which has many of their records.



BIRTHS:  Data given is for 2009 breeding season.

Males born:   66                   Females born:         48       Unknown sex born:  134

Number of pairs recommended for breeding: ?

Number of pairs bred: ?

Number of juveniles surviving to 6 months of age (25% survival to 6 mos of age):

            MALES:  mother-reared:     37                   hand-reared: 0

            FEMALES: mother-reared: 26                   hand-reared: 0



ANESTHESTIC PROTOCOLS (Please list successful and unsuccessful protocols):

Chamber induction with isoflurane followed by maintenance with mask isoflurane at approx 3% flow rate. Very successful.

Rabbits were premedicated with medetomidine before isoflurane induction many years ago because we worried the rabbits would breath-hold and arrest during anesthetic induction. However, pygmy rabbits do not appear to do this, and isoflurane induction without medetomidine has been much more straightforward.

Analgesics have included butorphanol for short-term injectable needs and meloxicam orally for long-term use. Dosages have been based on domestic rabbit literature, but sometimes scaled up due to the rabbits’ small size (e.g. meloxicam 0.5 mg/kg PO q24hrs).




VACCINE RECOMMENDATIONS ( including: Vaccine reactions, new vaccines to be considered):

No vaccines recommended or tried.


CONTRACEPTION (Methods used, successes, failures):

Separation of males and females – successful.

No chemical contraceptives have been tried.



None related to captive propagation. Release strategies are being investigated by staff at WSU. Previous research projects have involved retrospective analysis of breeding behaviors including mate preference, etc.




Pygmy rabbits require big sagebrush (Artemisia tridentata, not a true sage) as part of their diet, with as much as 90% of their winter diet being the leaves of this plant.

Captive diets include ad lib grass hay (timothy or orchard grass), ad lib Artemisia, formulated domestic rabbit pellets (Purina "Advanced Professional Rabbit”, approx 1/3 cup per rabbit), small amounts of fresh green produce (e.g. dandelion greens or clover leaves), and supplemental vitamin E (Emcelle by Stuart Products, 500 IU/ml,  2.5 IU per adult rabbit daily which is approx 6.25 IU/kg rabbit body weight).





Diarrhea patients are being managed with less carbohydrate in their diet. This means a smaller quantity of pellets and no fresh greens being offered, at least in the wintertime.

Due to risk of coccidiosis in juveniles, all juveniles (up to 3 months old) receive ponazuril 30 mg/kg PO weekly. Adult females during the breeding season also receive ponazuril 30 mg/kg PO weekly in an attempt to reduce coccidial oocyst contamination of enclosures that intermittently house neonates. All rabbits regardless of age receive ponazuril in the week prior to shipment to another facility and in the week after shipment from another facility, due to presumed stress-induced immunosuppression and higher risk of coccidial morbidity and mortality.








Release of approximately 20 rabbits to the wild was done in 2007. None survived longer than a few months, although one conceived and gave birth in the wild. This was a relatively "hard” release style.

Another release is tentatively planned in fall 2010 or winter 2011. This will very likely include all of the captive-held rabbits, therefore the captive propagation program will end at that time.

USFWS and Washington Dept of Fish and Wildlife are coordinating the plans for the release, since they are the 2 lead organizations running the pygmy rabbit recovery program.






(What bibliography/website?)


1) Harrenstien, Lisa A.; Finnegan, Mitchell V.; Woodford, Nina L.; Mansfield, Kristin G.; Waters, W. Ray; Bannantine, John P.; Paustian, Michael L.; Garner, Michael M.; Bakke, Antony C.; Peloquin, Charles A.; Phillips, Terry M. Mycobacterium avium in pygmy rabbits (Brachylagus idahoensis): 28 cases. Journal of Zoo & Wildlife Medicine. 37(4). DEC 2006. 498-512.


  The Columbia basin subpopulation of pygmy rabbit Brachylagus idahoensis was listed as endangered by the United States Fish and Wildlife Service in November 2001, and no pygmy rabbits have been seen in the wild since spring 2002. Captive propagation efforts have attempted to increase population size in preparation for reintroduction of animals into central Washington. Disseminated mycobacteriosis due to Mycobacterium avium has been the most common cause of death of adult captive pygmy rabbits. Between June 2002 and September 2004, mycobacteriosis was diagnosed in 28 captive adult pygmy rabbits (representing 29% of the captive population), in contrast to 18 adult pygmy rabbits dying of all other causes in the same time period. Antemortem and postmortem medical records were evaluated retrospectively to describe the clinical course of mycobacteriosis in pygmy rabbits, physical examination findings, and diagnostic test results in the diagnosis of mycobacteriosis in pygmy rabbits. Various treatment protocols, possible risk factors for mortality. and recommendations for prevention of mycobacteriosis were evaluated also. Compromised cell-mediated immunity appears to be the best explanation at this time for the observed high morbidity and mortality from mycobacterial infections in pygmy rabbits.


2) Himes, J. G.; Drohan, P. J.  Distribution and habitat selection of the pygmy rabbit, Brachylagus idahoensis, in Nevada (USA). Journal of Arid Environments. 68(3). FEB 2007. 371-382.


  We surveyed for pygmy rabbits, Brachylagus idahoensis, in Summer 2003 in Nevada (USA) to better determine the distribution, habitat, and soil patterns of this potentially threatened species. Pygmy rabbits and/or their sign (burrows and fecal pellets) were observed at 261 of 643 survey sites and their known distribution was extended 12 km to the south. Data on topography, soil, lithology, and hydrology were compared between sagebrush habitats where pygmy rabbits and/or their sign was present and absent. A predictive equation was produced and used as a model for characterizing habitats where pygmy rabbits were present. This model successfully explained the occurrence of pygmy rabbits and/or their sign on 56.7% of the surveyed transects. Sites occupied by pygmy rabbits were closer to perennial streams, had deeper soils, and had more northerly aspects than did unoccupied sites. Burrows and pellets were excellent indicators of the occurrence of pygmy rabbits, and thus should be!

  considered indicators of the presence of rabbits when conducting surveys in similar ecosystems due to the difficulty of observing rabbits in tall, dense stands of sagebrush where they are most common. The results of this survey indicate that pygmy rabbits are not as uncommon in Nevada as previously thought.


3) Shipley, Lisa A.; Davila, Tara B.; Thines, Nicole J.; Elias, Becky A. Nutritional requirements and diet choices of the pygmy rabbit (Brachylagus idahoensis): A sagebrush specialist. Journal of Chemical Ecology. 32(11). NOV 2006. 2455-2474.


  Sagebrush (Artemisia tridentata) comprises up to 99% of the winter and 50% of the summer diets of pygmy rabbits (Brachylagus idahoensis). Few animals specialize on such plants as sagebrush, which contain high levels of plant chemicals that can be toxic. We investigated the nutritional requirements of pygmy rabbits and their ability and propensity to consume sagebrush alone and as part of a mixed diet. We compared diet choices of pygmy rabbits with that of a generalist forager, the eastern cottontail (Sylvilagus floridanus). Pygmy rabbits had a moderately low nitrogen requirement (306.5 mg N/kg(0.75)/d), but a relatively high energy requirement, needing 750.8 kJ digestible energy/kg(0.75)/d to maintain their body mass while residing in small cages. They digested fiber in pelleted diets similarly to other small hindgut fermenters, but both cottontails and pygmy rabbits digested the fiber in sagebrush better than expected based on its indigestible acid detergent lignin content. Pygmy rabbits consumed more sagebrush than cottontails, regardless of the amount and nutritional quality of supplemental pellets provided. When consuming sagebrush alone, they ate barely enough to meet their energy requirements, whereas cottontails ate only enough sagebrush to meet 67% of theirs. Both rabbit species ate more sagebrush as the quality and quantity of supplemental pellets declined, and more greenhouse-grown sagebrush than sagebrush grown outside. Urine was more acidic when consuming sagebrush than when consuming pellets, indicating detoxification by the liver. Pygmy rabbits do not require sagebrush to survive, but seem to tolerate terpenes and other plant chemicals in sagebrush better than cottontails do.


4) Heady, Laura T.; Laundre, John W. Habitat use patterns within the home range of pygmy rabbits (Brachylagus idahoensis) in Southeastern Idaho. Western North American Naturalist. 65(4). OCT 2005. 490-500.


  Pygmy rabbits (Brachylagus idahoensis) are it small sagebrush (Artemisia tridentata) obligate lagomorph found within the Great Basin of northwestern United States. Because of its reliance oil sagebrush, this species is thought to be experiencing a major range reduction as a result of loss of sagebrush habitat. To aid in conservation of this species, we need to better understand its use of the sagebrush environment. We estimated summer home range rise patterns by relocating 5 radio-collared pygmy rabbits (3 females and 2 males) over a 24-hour cycle. We then compared soil texture, shrub density, height, mid canopy cover between areas close to burrow entrances and areas of high use and low use. Mean home range sizes of female and male rabbits were 37.2 and 67.9 ha, respectively Rabbits had disproportionate amounts of time (68.4% +/- 9.1, s((x) over bar)) and travel (63.0% +/- 5.7, s((x) over bar)) in areas within a 60-m radius of their burrows. Soil texture did not differ among the 3 areas, but shrub density, specifically big sagebrush, and forb density were significantly higher close to the bill-row than ill the high- and low-use areas. We conclude that pygmy rabbits are possibly borrow obligates and that their abundance and distribution are likely limited by available borrow sites.


5) Duszynski, Donald W.; Harrenstien, Lisa; Couch, Lee; Garner, Michael M. A pathogenic new species of Eimeria from the pygmy rabbit, Brachylagus idahoensis, in Washington and Oregon, with description of the sporulated oocyst and intestinal endogenous stages. Journal of Parasitology. 91(3). JUN 2005. 618-623.


  In January 2003. fecal samples from 13 live pygmy rabbits, Brachylagus idahoensis (Merriam, 1891), were collected at the Oregon Zoo in Portland, Oregon, and sent to the University of New Mexico (UNM), Albuquerque, New Mexico, to be examined for coccidia. In July 2004, 14 more fecal samples were collected and sent to UNM, 6 from some of the same rabbits and 8 from 16 other rabbits (4 were pooled samples from siblings). In addition, tissue sections from 3 dead rabbits (2 from the Oregon Zoo, I from Washington State University) also were examined. Two of 4 (50%) pooled fecal samples and 8 of 17 (47%) rabbit samples were positive for a single species of Eimeria, which we describe here as a new species. Sporulated oocysts were subspheroidal, 25.6 X 23.8 (22-28 X 21-27) mu m, with a length:width (L:W) ratio of 1.1 (1.0-1.2). A micropyle (similar to 2 mu m wide) and 0-1 polar granules were present, but an oocyst residuum was absent. Sporocysts were ellipsoidal, 13.4 X 8.1 (11-16.5 X 7.5-9) mu m, with a L:W ratio of 1.7 (1.3-2.2), and they had a Stieda body and sporocyst residuum. Tissue sections showed a heavy infection of the villous epithelial cells of the proximal and mid-small intestine with coccidial endogenous stages, but no stages were found in liver hepatocytes. Meronts with approximately 46 (26-70) merozoites per infected cell appeared to be fully developed and were subspheroidal, 14.8 X 13.9 (13-18 X 10.5-16.5) mu m. Developing macro- and microgamonts were indistinguishable from each other and were spheroidal to subspheroidal, 10.4 X 9.5 (9-11 X 7.5-10.5) mu m. Mature macrogamonts were spheroidal to subspheroidal, 14.2 X 13.7 (12-17 X 11-16) mu m, and mature microgamonts were smaller and subspheroidal, 11.9 X 10.8 (10.5-13 X 9-12) mu m. This eimerian seems to be extremely pathogenic to young pygmy rabbits, and given the precarious nature of this unique genetic population, it appears to be an emerging pathogen that deserves immediate further study.


6) Lyman, R. Lee. Biogeographic and conservation implications of late quaternary pygmy rabbits (Brachylagus idahoensis) in eastern Washington. Western North American Naturalist. 64(1). February 2004. 1-6.


  Five implications of a biogeographic model of pygmy rabbits (Brachylagus idahoensis) in eastern Washington proposed in 1991 are confirmed by 11 new late-Quaternary records. Pygmy rabbits from eastern Oregon colonized eastern Washington during the late Pleistocene and occupied their largest rang during the middle and late Holocene. Disjunction of the eastern Washington population from that in eastern Oregon occurred during at least the late Holocene. Nineteenth-century cattle grazing and 20th-century agricultural practices reduced habitat preferred by pygmy rabbits. Conservation of the small remaining population of pygmy rabbits will necessitate altered land use practices.


 7) Gabler, Kate I.; Heady, Laura T.; Laundre, John W.  A habitat suitability model for pygmy rabbits (Brachylagus idahoensis) in southeastern Idaho. Western North American Naturalist. 61(4). October, 2001. 480-489.


  A habitat suitability model was developed for pygmy rabbit (Brachylagus idahoensis) habitat on the Idaho National Engineering and Environmental Laboratory (INEEL) in southeastern Idaho. Suitable pygmy rabbit areas were characterized by greater cover and density of total shrubs and big sagebrush (Artemisia tridentata), as well as greater forb cover. Soil texture also played an important role in distinguishing suitable pygmy rabbit areas from nonuse sites. Principal components analysis (PCA) of several vegetation variables and soil texture was used to develop a habitat suitability model for pygmy rabbit habitat. This model, which can be used to successfully distinguish between pygmy rabbit use and nonuse areas on the INEEL, has the potential for use throughout the pygmy rabbit's range.




  The historic distribution of pygmy rabbits (Brachylagus idahoensis) is discontinuous between the Great Basin and eastern Washington. Available data indicate disjunction may have occurred during the latest Pleistocene and earliest Holocene. Extralimital records indicate that the range of the pygmy rabbit decreased in eastern Washington during the last 3,000 years as the extent of sagebrush (Artemisia tridentata)-dominated steppe diminished. Relative abundances of pygmy rabbits and pocket gophers (Thomomys talpoides) in eastern Washington also appears to reflect responses to changes in the distribution and abundance of sagebrush.


9) Estes-Zumpf, Wendy A.; Rachlow, Janet L. Evaluation of radio-transmitters on juvenile rabbits: Application to the semifossorial pygmy rabbit (Brachylagus idahoensis). Western North American Naturalist. 67(1). JAN 2007. 133-136.


10) Rachlow, Janet L.; Sanchez, Dana M.; Estes-Zumpf, Wendy A. Natal burrows and nests of free-ranging pygmy rabbits (Brachylagus idahoensis). Western North American Naturalist. 65(1). January 2005. 136-139.


11) Thines, Nicole J. Siegel; Shipley, Lisa A.; Sayler, Rodney D. Effects of cattle grazing on ecology and habitat of Columbia Basin pygmy rabbits (Brachylagus idahoensis). Biological Conservation. 119(4). October 2004. 525-534.


  Dramatic declines in the endangered Columbia Basin pygmy rabbit, a genetically unique population of small, burrowing rabbits in Northwestern United States, are likely the combined results of habitat degradation and fragmentation, disease, and predation. A critical component of pygmy rabbit habitat includes big sagebrush (Artemisia tridentata), which constitutes 82-99% of their winter diet and 10-50% of their summer diet. Sagebrush also forms the bulk of hiding cover around burrow sites. Across the range of pygmy rabbits, sagebrush habitat is grazed extensively by cattle. However, grazing has unknown effects on pygmy rabbits inhabiting the remaining, fragmented shrub-steppe habitat. We evaluated the effects of four grazing treatments on the distribution of pygmy rabbit burrows, diets of pygmy rabbits, and quality and quantity of vegetation at Sagebrush Flat in central Washington. Ungrazed areas contained significantly more burrows per unit area than did grazed areas. Vegetation composition and structure differed little among treatments in early summer before annual grazing by cattle. However, cattle grazing in late summer through winter removed about 50% of the grass cover, and reduced the nutritional quality (e.g., increased fiber and decreased protein) of the remaining grass. Although pygmy rabbits ate <2% grasses in winter, grasses and forbs comprised 53% of late summer diets. Because these endangered rabbits avoided grazed areas, removing cattle grazing from key habitat locations may benefit efforts to restore this rabbit in Washington. Copyright 2004 Elsevier Ltd. All rights reserved.


12) Katzner, Todd E.; Parker, Katherine L.; Harlow, Henry H. Metabolism and thermal response in winter-acclimatized pygmy rabbits (Brachylagus idahoensis). Journal of Mammalogy. 78(4). Nov., 1997. 1053-1062.


  Resting metabolic rate of pygmy rabbits (0.89 ml O2 g-1 h-1) was high compared to other eutherian mammals, but not unusual among lagomorphs. The estimated size of the zone of thermoneutrality was ca. 8-9degree C, with the lower critical temperature occurring between 15 and 20degree C, depending on body mass. Minimum thermal conductance was lower and mean body temperature was higher than predicted for similarly sized mammals. Body temperature fluctuated > 1degree C within a 24-h period, but showed no circadian patterns. Pygmy rabbits are thermally stressed during harsh winters in Wyoming, but low thermal conductance, a high-energy source of food, and favorable microenvironments enhance survival.


13) Katzner, Todd E.; Parker, Katherine L. Vegetative characteristics and size of home ranges used by pygmy rabbits (Brachylagus idahoensis) during winter. Journal of Mammalogy. 78(4). Nov., 1997. 1063-1072.


  We determined sizes of home ranges for pygmy rabbits in southwestern Wyoming and characterized the vegetation within and outside those areas used during winters of 1993 and 1994. Seventy percent of pygmy rabbits used more than one core area within their home range. Habitats within home ranges had less low ground cover and a greater number of wider, taller Artemisia tridentata than did adjacent non-used areas. Pygmy rabbits selectively used dense and structurally diverse stands of A. t. tridentata, which also accumulated more snow than areas of low use. Structure and diversity of vegetation above the snow's surface declined as the season progressed and depths of snow increased. The sub-nivean environment provided access to a relatively constant supply of food and provided protection from predators and thermal extremes. We suggest that size of home ranges used by pygmy rabbits is influenced more by amount of vegetative cover than by forage.


14) Heady, Laura T.; Gabler, Kate I.; Laundre, John W. Habitat and behavior assessment of an endemic, C-2 rabbit species (Brachylagus idahoensis) in southeastern Idaho. Bulletin of the Ecological Society of America. 77(3 SUPPL. PART 2). 1996. 188.


15) Ramos, Colleen N. An Irvingtonian species of Brachylagus (Mammalia: Lagomorpha) from Porcupine Cave, Park County, Colorado. Great Basin Naturalist. 59(2). April, 1999. 151-159.


  Brachylagus is currently a monotypic genus of uncertain origins and known only from Holocene and late Rancholabrean. A new species of leporid is described from the early and middle Pleistocene (Irvingtonian) deposits of Porcupine Cave, Park County, Colorado. Stratified deposits of the Pit and the Velvet Room, 2 localities within Porcupine Cave, have been dated biochronologically and paleomagnetically from the middle Irvingtonian and early to middle Irvingtonian, respectively. Brachylagus coloradoensis, sp. nov., is characterized by its conserved p3 enamel patterns which are intermediate between B. idahoensis and Hypolagus, and its size which is slightly larger than that of B. idahoensis. This suggests a possible ancestral relationship between Hypolagus and Brachylagus.


16) Larrucea, Eveline S.; Brussard, Peter F. A method for capturing pygmy rabbits in summer. Journal of Wildlife Management. 71(3). MAY 2007. 1016-1018.


  Degradation of sagebrush habitat and a lack of information on current status motivated a petition to list the pygmy rabbit (Brachylagus idahoensis) as threatened or endangered under the Endangered Species Act. The petition brought on renewed interest in obtaining data on pygmy rabbits; however, pygmy rabbits are notoriously difficult to capture, especially in summer. We tested box-trap, net, noose-pole, and fabric-fence methods to capture pygmy rabbits in 4 areas of northern Nevada and eastern California, USA. We captured 25 different pygmy rabbits in 30 captures from April 2005 to July 2006. The combination of camouflaged box traps baited with canned green beans was 35 % more successful and required less effort per captured rabbit than any other method. Noose-pole methods also were successful. These techniques provide an efficient method of capturing pygmy rabbits in summer when many remote field sites are most accessible.


17) Thines, Nicole J.; Shipley, Lisa A.; Bassman, John H.; Fellman, John K.; Mattison, D. Scott; Slusser, James R.; Gao, Wei. Effects of enhanced UV-B radiation on plant chemistry: nutritional consequences for a specialist and generalist lagomorphs. Journal of Chemical Ecology. 33(5). MAY 2007. 1025-1039.


  Ultraviolet-B (UV-B) radiation has been increasing in temperate latitudes in recent decades and is expected to continue rising for some time. Enhanced UV-B radiation can change plant chemistry, yet the effects of these changes on mammalian herbivores are unknown. To examine the influence of enhanced UV-B radiation on nutrition of a specialist and generalist hindgut fermenter, we measured nutritional and chemical constituents of three common North American range plants, big sagebrush (Artemisia tridentata), yarrow (Achillea millefolium), and bluebunch wheatgrass (Pseudoregneria spicata), and how these changes influenced in vitro dry matter digestibility and in vivo digestibility by pygmy rabbits (Brachylagus idahoensis) and eastern cottontails (Sylvilagus floridanus). Forages were irradiated for 3 mo with ambient (1 X) or supplemental (1.6X) UV-B radiation representing a 15% ozone depletion for Pullman, WA, USA. Enhanced UV-B radiation had minimal effects on the nutritional content and the tannin-binding capacity of forages. Similarly, the terpene concentration in sagebrush and yarrow was not affected by higher UV-B irradiances. Flavonoid compounds increased in sagebrush but decreased in yarrow. Rabbit preference and intake was not affected by treatment levels for any forage species and no differences were found between treatments for dry matter, fiber, protein digestibility, and apparent digestible energy.


18) Durden, Lance A.; Rausch, Robert L. Haemodipsus brachylagi N. sp (Phthiraptera : Anoplura : polyplacidae), a new sucking louse from the pygmy rabbit in Nevada. Journal of Parasitology. 93(2). APR 2007. 247-251.


  The male and female of Haemodipsis brachylagi n. sp. (Phthiraptera: Anoplura) are described from specimens collected from a pygmy rabbit, Brachylagus idahoensis (Merriam) (Lagomorpha: Leporidae), from Nevada. Morphological features that differentiate the new species from other known species of Haemodipsus are elucidated, and an identification key to both sexes of the 3 species now known from this genus in North America is included. Geographical distributions of the other 4 species of Haemodipsus known from other parts of the world are highlighted.


19) Elias, Becky A.; Shipley, Lisa A.; Sayler, Rodney D.; Lamson, Rachel S. Mating and parental care in captive pygmy rabbits. Journal of Mammalogy. 87(5). OCT 2006. 921-928.


  As part of a captive-breeding program to restore extirpated Columbia Basin pygmy rabbits (Brachylagus idahoensis) to their native habitat in Washington, we documented mating and parental care behavior of these lagomorphs, which was previously unknown. Pygmy rabbits bred from late February through early June, and mating behavior consisted of chasing and brief copulations. Although presented with 1-4 mating partners and 1-6 mating opportunities annually, only 74% of females became pregnant each year. Unlike other lagomorphs, females dug a 16- to 35-cm natal burrow, usually separate from the residential burrow system, an average of 13 days after a successful copulation. Twenty-four days after copulation, females gave birth to 2-7 young at the entrance of the natal burrow and then covered the entrance. Females returned to nurse 1 or 2 times per day, until young emerged from burrows about 15 days after birth. Females averaged 1.3 litters per year, rarely (2%) producing 4 litters. Except for digging a natal burrow, mating and parental care in pygmy rabbits is similar to that of other lagomorphs. Understanding reproductive behavior is critical for captive breeding and reintroduction of pygmy rabbits, and efforts to reduce the consequences of genetic bottlenecks and inbreeding in captivity.


20) Rachlow, Janet L.; Svancara, Leona K. Prioritizing habitat for surveys of an uncommon mammal: A modeling approach applied to pygmy rabbits. Journal of Mammalogy. 87(5). OCT 2006. 827-833.


  Determining occurrence and distribution is an essential 1st step in conservation planning for rare species. Spatial habitat models can be used to increase efficiency of field surveys and to improve understanding about factors influencing animal distributions. We used a modeling approach to identify and prioritize potential habitat for survey efforts for an uncommon mammal, the pygmy rabbit (Brachylagus idahoensis), for which detailed habitat data are limited. A base map of potential habitat in Idaho was defined using vegetation type and soil depth data. Documented locations (n=164) were used to evaluate additional habitat variables to prioritize the potential habitat for surveys. We conducted field surveys to evaluate the predicted habitat attributes and document presence or absence of the species. Newly confirmed occurrences (n=112) and absences (n=139) were used to assess accuracy in predicting habitat priority ratings. Overall model accuracy was 65%. Eighty-four percent of the new occurrences were located in the 2 highest priority ranks, and < 0.4% were located in the 2 lowest priority ranks. We offer several examples of how survey results can be used to improve the habitat model and increase efficiency of future survey efforts.


21) Murray, Lyndon K.; Bell, Christopher J.; Dolan, M. Timothy; Mead, Jim I. Late Pleistocene fauna from the southern Colorado Plateau, Navaj County, Arizona. Southwestern Naturalist. 50(3). SEP 2005. 363-374.


  We discovered a mandible of the flat-headed peccary (Platygonus compressus) in a sand and gravel borrow pit (Pit Stop Quarry) between Taylor and Show Low, Navajo County, Arizona. We also found isolated skeletal elements of a mole salamander (Ambystomatidae), pygmy rabbit (Brachylagus idahoensis), sagebrush vole (Lemmiscus curtains), and several other small mammals in sediments immediately surrounding the peccary jaw. The presence of P. compressus indicates that the deposit is of late Pleistocene age. Specimens also represent the first Pleistocene record of Ambystomatidae on the Colorado Plateau, an important additional record of R compressus on the Colorado Plateau, and 1 of 2 records of B. idahoensis in Arizona.


22) Schmitt, Dave N.; Madsen, David B.; Lupo, Karen D. Small-mammal data on early and middle Holocene climates and biotic communities in the Bonneville Basin, USA. Quaternary Research (Orlando). 58(3). November 2002. 255-260.


  Archaeological investigations in Camels Back Cave, western Utah, recovered a series of small-mammal bone assemblages from stratified deposits dating between ca. 12,000 and 500 14C yr B.P. The cave's early Holocene fauna includes a number of species adapted to montane or mesic habitats containing grasses and/or sagebrush (e.g., Lepus townsendii, Marmota flaviventris, Reithrodontomys megalotis, and Brachylagus idahoensis) which suggest that the region was relatively cool and moist until after 8800 14C yr B.P. Between ca. 8600 and 8100 14C yr B.P. these mammals became locally extinct, taxonomic diversity declined, and there was an increase in species well-adapted to xeric, low-elevation habitats, including ground squirrels, Lepus californicus and Neotoma lepida. The early small-mammal record from Camels Back Cave is similar to the 11,300-6000 14C yr B.P. mammalian sequence from Homestead Cave, northwestern Utah, and provides corroborative data on Bonneville Basin paleoenvironments and mammalian responses to middle Holocene desertification.


23) Gabler, Kate I.; Laundre, John W.; Heady, Laura T. Predicting the suitability of habitat in southeast Idaho for pygmy rabbits. Journal of Wildlife Management. 64(3). July, 2000. 759-764.


  A geographic information system (GIS) model was developed for pygmy rabbit (Brachylagus idahoensis) habitat in southeastern Idaho. Areas of potential use by pygmy rabbits were determined from appropriate vegetation and geological classes in a GIS analysis. Sites most likely to be occupied within potential vegetation and geologic habitat were determined by including appropriate slope and aspect measurements. Randomly selected areas within and outside of predicted areas were searched for pygmy rabbit sign. This resulted in a 57% probability of predicting areas occupied by pygmy rabbits and a 100% probability of predicting areas not occupied. Our model may be useful in identifying areas unsuitable for pygmy-rabbits and it is a useful first step in identifying appropriate habitat for the pygmy rabbit, potentially throughout their range.


24) Halanych, Kenneth M.; Robinson, Terence J. Phylogenetic relationships of cottontails (Sylvilagus, Lagomorpha): Congruence of 12S rDNA and cytogenetic data. Molecular Phylogenetics & Evolution. 7(3). 1997. 294-302.


  The genus Sylvilagus, which comprises the New World cottontail rabbits, contains several commercially important as well as endangered (or threatened) species. Understanding the evolution of this group is pertinent to their management and conservation. The purpose of this study was to examine the evolutionary history of the cottontails using sequence data from the mitochondrial 12S rRNA gene. The 12S data provide a robust phylogeny which was supported under a variety of phylogenetic approaches and transition/transversion (Ti/Tv) weighing schemes. Stem and loop regions of the gene were analyzed separately and two different methods of estimating Ti/Tv ratios were employed. The phylogeny obtained was consistent with available cytogenetic information. The 12S data indicate that separate generic status for the pygmy rabbit, Brachylagus idahoensis, is warranted based on its phylogenetic position and sequence divergence values. Additionally, the taxa which are geographically adjac!

 ent are also phylogenetically closely related; for example, the marsh rabbit, S. palustris, and the swamp rabbit, S. aquaticus, are sister taxa, as are the mountain cottontail, S. nuttallii, and desert cottontail, S. audubonii. This finding suggests that recent vicariance events might explain the diversification of several cottontail lineages.


25) Robinson, T. J.; Matthee, C. A. Phylogeny and evolutionary origins of the Leporidae: a review of cytogenetics, molecular analyses and a supermatrix analysis. Mammal Review. 35(3-4). JUL-OCT 2005. 231-247.


  1. We review current knowledge of the evolutionary relationships among species of Leporidae drawing on molecular, cytogenetic and morphological data. We highlight problems associated with retrieving phylogenetic information under conditions of a rapid radiation and the lack of phylogenetically informative cytogenetic and mitochondrial DNA characters. Most morphological features underpinning generic distinctions are subtle and prone to reversal and convergence and as a consequence, they generally provide little basis for assessing phylogenetic affinity.2. We report the results of a supermatrix analysis that combines published nucleotide sequence data, unique insertion/deletion events, morphological characters and presumed geographical centres of origin of each genus. This represents the most comprehensive intergeneric comparison of the Leporidae thus far undertaken.3. The monophyly of the 11 leporid genera is unambiguously supported. There is support for an Afroasian assemb!

 lage that comprises Poelagus, Pronolagus and Nesolagus, a primitive Lepus, with the problematic Bunolagus, Oryctolagus, Caprolagus and Pentalagus as derived species in a clade that also includes the closely related Brachylagus and Sylvilagus as sister taxa.4. There is no support for the Palaeolaginae, although Romerolagus is an ancient lineage within the extant Leporidae.5. We hold that of the polytypic genera Lepus remains the most problematic, and provide a working hypothesis that will hopefully encourage future research on the various hare species.


26) Averianov, Alexander O.; Tesakov, Alexey S. Evolutionary trends in Mio-Pliocene Leporinae, based on Trischizolagus (Mammalia, Lagomorpha). Palaontologische Zeitschrift. 71(1-2). 1997. 145-153.


  New material of Trischizolagus dumitrescuae from Moldova and Ukraine is described. The variation of p3 in Trischizolagus shows the gradual shift of morphotype frequencies from the 'Hypolagus' pattern in Turolian through the mixture of three patterns (including 'Nekrolagus' morphotype) in Early Ruscinian to the dominant 'Alilepus' pattern in the Late Ruscinian samples. These transformations took place parallel to that of the North American Nekrolagus. Probably North American Sylvilagus, Brachylagus, and Romerolagus had an North American origin from Nekrolagus, whereas Eurasiatic and African Oryctolagus, Caprolagus, Nesolagus, and Poelagus could have originated in the Old World from Trischizolagus.


27) Larrucea, Eveline S.; Brussard, Peter F. Diel and Seasonal Activity Patterns of Pygmy Rabbits (Brachylagus idahoensis). Journal of Mammalogy 90(5): 1176-1183. 2009.


Characterizing circadian activity patterns is one of the essential steps to understanding how a species interacts with its environment. This study documented activity patterns of pygmy rabbits (Brachylagus idahoensis) in free-ranging populations at 5 sites in Nevada and California. Infrared-triggered camera systems were placed within areas occupied by populations of pygmy rabbits and operated for 1 year. The number of photographs obtained per hour was used as an index of aboveground activity. Activity was analyzed for diel and seasonal patterns as well as for differences among populations. All populations showed a bimodal diel activity pattern with most activity occurring at dawn and at dusk during all seasons. Greatest activity occurred at dawn except during winter. Four of the 5 study sites showed similar levels of activity. The atypical site was located 550 m higher in elevation at a locality known for extreme weather; activity levels were twice as high at that site. Activity patterns of pygmy rabbits likely reflect a combination of predation pressures as well as metabolic energy demands.


28) Wilson, Tammy L.; Odei, James B.; Hooten, Mevin B.; Edwards, Thomas C. Hierarchical spatial models for predicting pygmy rabbit distribution and relative abundance. Journal of Applied Ecology 2010 (online).


29) Estes-Zumpf, W. A.; Rachlow, J. L. Natal Dispersal by Pygmy Rabbits (Brachylagus idahoensis). Journal of Mammalogy 90(2): 363-372. 2009.


30) Price, Amanda J.; Estes-Zumpf, Wendy; Jachlow, Janet. Survival of Juvenile Pygmy Rabbits. Journal of Wildlife Mgmt 74(1): 43-47. 2010.


Until recently, natal behavior of pygmy rabbits (Brachylagus idahoensis) was largely unknown, and no information on survival of free-ranging juveniles was available. We evaluated survival of radiotagged juvenile pygmy rabbits at 2 sites in east-central Idaho, USA, during 2004 and 2005. We captured juveniles (n = 58) shortly after they emerged from natal burrows. Mortality rates were high and variable, ranging from 27% for females during 2004 to 63% for males during 2005. Approximately 69% of mortalities were attributed to predation. We evaluated variables influencing juvenile survival through 18 weeks old using known-fate models in Program MARK. We expected survival to decline around the age of natal dispersal and to be lower for young born later in the season. We evaluated 14 candidate models that included sex, year, study area, and relative date of birth within each year. Model selection results did not indicate strong support for any single combination of variables, and 8 competing models all included effects of relative date of birth, year, and study area. These results revealed substantial variability in survival of juveniles across multiple factors, and we documented similar patterns for adult pygmy rabbits. Such high variability in survival over relatively small spatial and temporal scales might contribute to marked fluctuations in populations of pygmy rabbits and, hence, managers interested in monitoring this species might consider monitoring multiple populations across broader geographic areas to assess regional trends in numbers.


31) Sanchez, Dana M.; Rachlow, Janet L.; Robinson, Andrew P.; Johnson, Timothy R. Survey indicators for pygmy rabbits: temporal trends of burrow systems and pellets. Western North Amer Naturalist 69(4). 2009.


Obtaining estimates of absolute abundance for rare or cryptic species can be challenging. In these cases,methods using indirect indicators such as sign might offer useful indices of population size. Pygmy rabbits (Brachylagus idahoensis) are small, burrowing lagomorphs for which methods for population assessment and monitoring are needed. Current tools for estimating relative abundance rely on detecting and assessing fecal pellets and burrow systems. We evaluated temporal changes in each of these indicators to gauge their potential usefulness as indicators of relative and absolute abundance of pygmy rabbits. Pellet persistence was strongly influenced by environmental exposure, and based on our data, we estimated that maximum persistence of fecal pellets would be 24–34 months. Pellet appearance (color) was affected by both time and exposure. Burrow systems were remarkably resilient over the course of the study. Probability of burrow systems transitioning between activity classes (active, recent, and old) did not vary detectably by study site, season, or year. We suggest that 2 protocols currently used for classification of pygmy rabbit burrow systems are most useful for different applications. Further work is needed, however, to link such assessments to quantitative estimates of population size.


32) Davies, Kirk W.; Bates, Jonathan D.; Johnson, Dustin D.; Nafus, Aleta M. Influence of mowing Artemisia tridentate ssp. Wyomingensis on winter habitat for wildlife. Environmental Mgmt 44(1): 84-92. 2009.


Mowing is commonly implemented to Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh (Wyoming big sagebrush) plant communities to improve wildlife habitat, increase forage production for livestock, and create fuel breaks for fire suppression. However, information detailing the influence of mowing on winter habitat for wildlife is lacking. This information is crucial because many wildlife species depended on A. tridentata spp. wyomingensis plant communities for winter habitat and consume significant quantities of Artemisia during this time. Furthermore, information is generally limited describing the recovery of A. tridentata spp. wyomingensis to mowing and the impacts of mowing on stand structure. Stand characteristics and Artemisia leaf tissue crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF) concentrations were measured in midwinter on 0-, 2-, 4-, and 6-year-old fall-applied mechanical (mowed at 20 cm height) treatments and compared to adjacent untreated (control) areas. Mowing compared to the control decreased Artemisia cover, density, canopy volume, canopy elliptical area, and height (P < 0.05), but all characteristics were recovering (P < 0.05). Mowing A. tridentata spp. wyomingensis plant communities slightly increases the nutritional quality of Artemisia leaves (P < 0.05), but it simultaneously results in up to 20 years of decrease in Artemisia structural characteristics. Because of the large reduction in A. tridentata spp. wyomingensis for potentially 20 years following mowing, mowing should not be applied in Artemisia facultative and obligate wildlife winter habitat. Considering the decline in A. tridentata spp. wyomingensis-dominated landscapes, we caution against mowing these communities.  


33) Shipley, Lisa A.; Forbey, Jennifer S.; Moore, Ben D. Revisiting the dietary niche: when is a mammalian herbivore a specialist? Integrative and Comparative Biology 2009 (on-line).



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