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Living OrganismsAnimalia / Craniata / Mammalia / Lagomorpha / Leporidae / Brachylagus / Species

Brachylagus idahoensis - Pygmy rabbit (Click photographs/illustrations for full picture & further details)

BE_Ant_Grasshopper_BabyPicr.jpg (61386 bytes) RS_IdahoPygmyRabbit.jpg (48624 bytes) RS_Pygmy_Rabbit_antenna.jpg (25611 bytes) RS_ReleasingPygRab.jpg (45757 bytes) RSSagebrushFlat.jpg (54839 bytes) RSPygmyRabbitFeedingSagebrush.jpg (68987 bytes) RSPygmyRabbit_YoungKit.jpg (28975 bytes) RSPygmyRabbit_YoungKit_cr.jpg (36874 bytes) TD_PygmyRabbitKits30.jpg (59911 bytes) TD_ArtificRabbitBurrowEntrance_7607cr.jpg (62315 bytes)

INDEX - INFORMATION AVAILABLE

GENERAL & REFERENCES

APPEARANCE / MORPHOLOGY

LIFE STAGES / NATURAL DIET / PHYSIOLOGY

BEHAVIOUR

HABITAT & RANGE

CONSERVATION

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General and References

Alternative Names (Synonyms)

  • Sylvilagus idahoensis. (B430.w2)(J469.125.w1)

Names for new-borns / juveniles

Names for males

Names for females

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General Appearance

Adult: 
  • This is the smallest of any of the North American rabbit species. (B285.w5c, B605.6.w6, J469.125.w1)
  • A buff-grey rabbit with short hind legs and short, rounded ears which are thickly haired both inside and out. (B147, B605.6.w6, J469.125.w1)

Newborn: At birth these kits have little fur; their eyes are closed. (J332.87.w1) 

Similar Species

--

Sexual Dimorphism

--

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References

Species Authors & Referees

Author: Kathryn Pintus BSc MSc MSc (V.w115); Dr Debra Bourne MA VetMB PhD MRCVS (V.w5

ORGANISATIONS

ELECTRONIC LIBRARY
(Further Reading)
Click image for full contents list of ELECTRONIC LIBRARY

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Husbandry Information

Notes

  • Pygmy rabbits have been kept successfully as individuals in 2.5 m diameter, 6 x 8 ft and 8 x 10 ft pens. In these pens, males and females are given access to one another for breeding by opening a door between pens; they cannot be kept together permanently. In larger pens (e.g. 75 mē, 100 mē), a female and two males have been kept; individuals of litters will tolerate one another in larger pens through summer and autumn if there are enough artificial burrows.
  • Solid galvanised metal, mesh hardware cloth (weldmesh) or hardware cloth inside chainlink has been used as fencing. This keeps rabbit in and prevents access by even small predators such as weasels. Further protection against predators involves crushed stone in a layer for 2 - 3 ft on the outside of the pen to discourage digging by predators, and an electric wire on the outside of the fence. 
  • Solid roofs or on larger pens 1 x 2 inch weldmesh provides overhead protection.
  • The floors of pens are solid or lined with 1 x 2 inch weldmesh, covered with natural soil substrate 0.5 - 1.0 m deep.
  • Soil substrate in which females can dig burrows appears to be extremely important for these rabbits to rear their young successfully. 
  • Pygmy rabbits have been successfully kept and bred on a diet of grain-forage pellets containing 35.6 - 49.3% neutral detergent fibre and 15.8 - 21.3% crude protein, plus daily fresh greens (about 40 g per day in the breeding season, 5 g per day the rest of the year, and clippings of big sagebrush Artemisia tridentata tridentata, 25 g per day during the breeding season and 15 g per day the rest of the year. (J332.87.w1)
    • Rabbits in large pens with additional access to natural vegetation (grasses and forbes, as well as more space, grew faster than those in small pens and reached higher weights (males 523g versus 424 g and females 590 g versus 431 g, at 26 weeks). (D373, V.w134)
    • Breeding of Columbia Basin pygmy rabbits was more successful on a higher protein diet. (W739.Jan09.w1)
  • Water is provided in bowls; these rabbits do not use drinking bottles.
  • Pygmy rabbits can be transported in a standard cardboard pet carrier. It is important to ensure that they do not overheat and are exposed to neither sun nor excessive wind during transportation; for example they can be transported at night to avoid excessive daytime temperatures. The box is lined with grass; a small quantity of pelleted food plus freshly cut forbes allows rabbits to eat during transport. (D373, V.w134)
  • Coloured wax has been used on the ear tips to identify individual. Brachylagus idahoensis - Pygmy rabbits. (V.w134)
  • Kits have been hand-reared using a kitten milk replacer, Critical Care formula and Nutri-Cal in addition to pelleted food and fresh greens. Probiotics and coccidiostats are also given.

(D373, J332.87.w1, V.w134, W739.Jan09.w1)

Management Techniques

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Appearance / Morphology

Measurement & Weight

Notes

Specific Brachylagus idahoensis Information
  • This is the smallest of any of the North American rabbit species, in terms of body size. (B430.w2, B605.6.w6)
  • Females are generally larger than the males. (B430.w2)

LENGTH
Adult:

  • Males 
    • Total length 252-285 (average 275) mm. (B430.w2, J469.125.w1)
  • Females
    • Total length 230-305 (average 283) mm. (B430.w2, J469.125.w1)
  • 21-27 cm. (B285.w5c)
  • 215-275 mm. (B147)

Newborns: --

HEIGHT
Adults and sub-adults: --
Juveniles: --

WEIGHT
Adult: 

Reported weights have varied between studies in different US states. (B605.6.w6)

  • Males 
    • California: mean body weight of 409 g (range 375-435 g). (B605.6.w6, J469.125.w1)
    • Utah: mean body weight of 405 g (range 373-428 g). (B605.6.w6, J469.125.w1)
    • Idaho: mean body weight of 418 g. (B605.6.w6, J469.125.w1)
    • 373-435 g (average: 411 g). (B430.w2)
  • Females 
    • California: mean body weight of 398 g (range 246-458 g). (B605.6.w6, J469.125.w1)
    • Utah: mean body weight of 436 g (range 415-456 g). (B605.6.w6, J469.125.w1)
    • Idaho: mean body weight 462 g. (B605.6.w6, J469.125.w1)
    • 415-458 g (average: 432 g). (B430.w2)

Newborns: --

GROWTH RATE

  • Depends on birth date, with juveniles from earlier litters having a longer pre-winter growth period than those from later litters. (J469.125.w1)

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Head and Neck

Notes

GENERAL HEAD STRUCTURE:
Adult:

Specific Brachylagus idahoensis Information

  • Short, rounded ears (B147, B430.w2, B605.6.w6, J469.125.w1) which are thickly haired both inside and out. (B430.w2, B605.6.w6, J469.125.w1)
  • Ears length males48 - 56 mm average 51 mm, females 48 - 51 mm average 70 mm. (J469.125.w1)
  • Skull
    • Short, pointed rostrum. (B147, J469.125.w1)
    • Relatively long supraorbital processes (compared with Sylvilagus sp.); "the postorbital extensions of the supraorbitals are broadest distally rather than tapering to a blunt end as in Sylvilagus." (B147)

Newborn: --

DENTITION:

General Information

  • Rabbits and hares have a total of 28 teeth. (B285.w5a)
  • The lower tooth rows are closer together than the upper tooth rows. (B147)
  • Lagomorphs differ from rodents by having two pairs of upper incisors rather than just the one pair. The additional set of incisors are called peg teeth and are found directly behind the long pair in the upper jaw. (B147, B285.w5a, B605.1.w1)
  • At birth, lagomorphs actually have three pairs of upper incisors, but they quickly lose the outer incisor on each side. (B147)
  • The incisors are covered completely by enamel. (B147)
  • The upper incisors' roots are found in the skull's premaxillary bones. However, the length of the lower incisors' roots varies. (B147)
    • [Note: lagomorphs have teeth which grow throughout their lives. For this reason the portion of the teeth which is not exposed (not above the gum line) is strictly speaking not a "root"; however, it is sometimes convenient to describe it as a root.]
  • The first upper incisors have a straight cutting edge. (B147)
  • The peg teeth lack a cutting edge. (B147)

EYES:
Adult:

General Information

  • Lagomorph eyes are positioned such that they allow for good broad-field vision. (B285.w5a)
  • Hares and rabbits have large eyes which are adapted to both their crepuscular and nocturnal activity patterns. (B285.w5b)
  • Leporids have "large eyes to increase visual acuity in dim light." (B430.w2)

Newborn:

Specific Brachylagus idahoensis Information

  • Eyes closed at birth. (J332.87.w1)

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Legs, Spine and Tracks

Notes

Specific Brachylagus idahoensis Information
  • This species has very short hind legs, with comparatively broad and heavily-furred hind feet. (B147, J469.125.w1)

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Tail

Notes

Specific Brachylagus idahoensis Information
  • Small tail with buff-coloured underside. (B147, B430.w2, B605.6.w6)
  • Bushy tail. (B285.w5c)
  • Small, inconspicuous. (B430.w2, J469.125.w1)

Length

  • 1.5-2 cm. (B147, B285.w5c, B430.w2)
  • Male
    • 15-20 mm. (B430.w2, B605.6.w6, J469.125.w1) average 17.5 mm. (J469.125.w1)
    • Average: 17 mm. (B430.w2)
  • Female
    • 15-24 mm. (B430.w2, B605.6.w6) average 15 - 19 mm, average 17 mm. (J469.125.w1)
    • Average: 18 mm. (B430.w2)

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Skin / Coat / Pelage

Notes

Adult: 

Specific Brachylagus idahoensis Information

  • This species has a long, greyish coat with a white abdomen and cinnamon buff coloured fur on the legs, chest and nape. (B605.6.w6)
  • Reddish coat. (B285.w5c)
  • "The upper parts are buffy gray and the underparts are white, often tinged with buff." (B147)
  • Thick fur both on and inside the ears. (B605.6.w6)
  • Upper parts buff grey with nape and anterior legs cinnamon buff, underside buff, ears edged in buff. Vibrissae black and white. (J469.125.w1)
  • Pygmy rabbits moult once a year, resulting in a very long, silky coat in the autumn. This autumn pelage is grey in colour on the upper parts, and white (frequently tinged with buff) on the abdomen. This silver-grey colour remains throughout the winter, although the fur becomes worn. During the spring and summer months, the pelage is a much darker grey. (B430.w2, J469.125.w1)

Adult Colour variations: --

Newborn / Juvenile:

  • There is little fur covering the skin at birth. (J332.87.w1)

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Detailed Anatomy Notes
(Summary information provided for pertinent species-specific data cross-referenced in Wildpro)

Notes

Female reproductive tract

Specific Brachylagus idahoensis Information

  • Females of this species have ten mammary glands. (B147, J469.125.w1)
Male reproductive tract

General Information

  • Males lack a baculum. (B147)
  • Testes are in the scrotum located in front of the penis. (B147)

Specific Brachylagus idahoensis Information

  • Prostate gland usually inconspicuous but measured at 27 mm long and 16 mm wide in rabbits in Utah in March-April. (J469.125.w1)

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Life Stages / Natural Diet / Physiology

Life Stages

Notes

BREEDING SEASON:

Specific Brachylagus idahoensis Information

  • In the western USA, this species mates in the spring and early summer. (B287)
  • In Idaho (USA), females of this species are known to conceive between the end of February and April. (B287)

OESTRUS / OVULATION:

General Information

Specific Brachylagus idahoensis Information

  • Differences in the timing and duration of female fertility in this species have been described for different states. (B605.6.w6)
    • Utah: late February through March. (B147, B605.6.w6)
    • Idaho: late March through late May. (B147, B605.6.w6)
  • In a captive breeding programme, successful copulations occurred 21st February to 17th June, peaking between the first wekk in April and the second week in May. (J332.87.w1)

GESTATION / PREGNANCY:

General Information

  • Under adverse conditions (such as during climatic or social stress), female lagomorphs are able to resorb embryos. (B285.w5a)
  • It is thought that some lagomorph species are able to conceive a second litter even before the last young is born; this is known as superfetation. (B285.w5a)

Specific Brachylagus idahoensis Information

  • "Pregnant females have been observed from late February through late May." (B430.w2)
  • Pregnant females have been found in Utah (USA) between late February and late March, whereas in Idaho (USA) pregnant females were found late March to May. (B287, J469.125.w1)
  • The gestation period for pygmy rabbits lasts from 26 to 28 days. (B147, B605.6.w6)
  • Gestation period has been reported to be 39 days (field data). (B287)
  • Gestation period observed in captive rabbits was 23.7 +/- 0.9 days (range 22.3 - 25.3 days). (J332.87.w1)

PARTURITION / BIRTH:

General Information

  • Newborn rabbits are born with very little or no fur, and their eyes do not open until 4-10 days after birth. (B285.w5b)
  • Rabbits produce altricial kittens (B285.w5b, B430.w2) which are born into fur-lined nests built either under dense cover or within underground chambers. (B285.w5b)

Specific Brachylagus idahoensis Information

  • There is a 1:1 sex ratio at birth. (B430.w2)
  • In northwestern USA, females are known to give birth in June and July. (B287)
  • Observations in captivity showed that of nine births, three occurred at night (0900 to 0500 hours), two in the morning (0500 to 1200 hr) and four in the afternoon (1200 - 1900hr). Just before parturition, the female would open the natal burrow (dug previously), , clean herself and pluck fur from her belly, collect hay and place it in the burrow. Two females gave birth inside the natal burrow while seven gave birth at the entrance to the burrow. During parturition, "females pushed their abdomens against the ground, squatted, sat back slightly on their hind feet, or hunched over (sometimes directly over the natal burrow)." Parturition took 14.8 +/- 4.5 minutes. Young crawled into the burrow or were carried in by the doe. The doe then covered the opening to the natal burrow with soil and with hay or twigs. (J332.87.w1)

Neonatal / Development:

General Information

  • Young leporids are only suckled briefly once every 24 hours. (B285.w5b)

  • Rabbit kittens remain together within their breeding chambers. (B285.w5b)

Specific Brachylagus idahoensis Information

Data from detailed observations of captive rabbits:

  • Newborns, although blind, often crawl from the entrance to the natal burrow (where they are born) into the burrow. (J332.87.w1)
  • During the first weeks they live in the burrow, but often make their own way to the entrance of the burrow to be nursed (sometimes they are carried by the female) and then crawl back into the burrow (or are carried by the female). (J332.87.w1)
  • In the several days before final emergence they may spend several minutes outside the burrow after suckling before being put back into the nest. (J332.87.w1)
  • Permanent emergence occurs at 15.4 +/- 1.3 days old: at this time the female does not re-cover the burrow entrance after nursing. (J332.87.w1) 
    • On one occasion the kits dug themselves out of the burrow at 14 days old and the female made no attempt to put them back into the natal burrow. (J332.87.w1)
  • Within 1 - 2 days after emergence, kits start feeding on vegetation. (J332.87.w1)
  • After permanent emergence, suckling is generally initiate by the young while the female is eating; females will often become intolerant of the young at this stage, chasing and biting young which try to nurse. (J332.87.w1)

LITTER SIZE: 

Specific Brachylagus idahoensis Information

  • The average litter size for this species is six (B430.w2, B605.6.w6, (J469.125.w1)), but ranges from five to eight (B605.6.w6) four to eight offspring. (B147)
  • Litter size varies within this species; a maximum of six has been reported, though there have also been reports of the presence of up to eight embryos. (B287)
  • Litter sizes observed in captivity were 2 - 7, average 4.1 +/- 0.1 per litter. (J332.87.w1)

TIME BETWEEN LITTERS / LITTERS PER YEAR:

General Information

  • The inter-birth interval in lagomorphs is reduced by the phenomenon of induced ovulation, and post-partum oestrus, which allows females to conceive immediately after they have given birth. (B285.w5a)

Specific Brachylagus idahoensis Information

  • Two (B287) or three litters per year can be produced. (B147, B430.w2, B605.6.w6)
  • Maximum three per year. (J469.125.w1)
  • Females in small pens produced a maximum of three litters per year; two females in large pens (with constant access to males) each produced four litters per year. (J332.87.w1)
  • The interlitter interval for this species is thought to be 39 days. (B287)

LACTATION / MILK PRODUCTION:

General Information

  • Leporids only release milk once in every 24 hour period. (B285.w5b)
  • Leporid milk has a very high fat and protein content, and as such is highly nutritious. Although the lactation period is brief, the milk is pumped into the young at a high speed. (B285.w5b)
  • The lactation period has a duration of between 17 and 23 days. (B285.w5b)

Specific Brachylagus idahoensis Information

  • Observations in captivity showed that the female sucked her young once (6/8 litters) or twice (2/8) a day. (J332.87.w1)

SEXUAL MATURITY: 

Specific Brachylagus idahoensis Information

  • The young Pygmy rabbits do not become fertile until the breeding season following their birth. (B147, B430.w2, (J469.125.w1)
  • Males: Spermatogenesis occurs at 6 months of age in this species. (B287)

MALE SEASONAL VARIATION: 

Specific Brachylagus idahoensis Information

  • Idaho: Testes start descending in mid-December, becoming fully scrotal by late January with copious sperm available by March. (J469.125.w1)
  • Utah: increasing size of tested from January to a peak in March. (J469.125.w1)
  • Regression of testes starts late June; this ot thought to be regulated by photoperiod. (J469.125.w1)
  • "Sexual development in males begins in January, peaks in March and declines in June." (B605.6.w6)
  • In Idaho (USA), spermatogenesis is reported for January to July, with none between August and December. There was no data for April to August. (B287)

LONGEVITY / MORTALITY:

General Information

  • Rabbits and hares in the wild live for less than a year on average; a maximum age of 12 years has been recorded in a couple of species. (B285.w5b)

Specific Brachylagus idahoensis Information

  • Mean annual adult mortality has been found to be as high as 88%, with greatest mortality occurring from January through March. (B430.w2, B605.6.w6)
  • Juvenile survival has been found to be very low, with mortality reaching more than 50% within the first five weeks of emergence (B605.6.w6). In one year of a study, mortality in the third cohort of reproduction reached 100%. (B605.6.w6)
  • During the first five weeks following birth, juvenile mortality is at its highest. (B430.w2, J469.125.w1)
  • Adult mortality highest late winter to early spring. (J469.125.w1)
  • A study has shown that the average age of females tends to be greater than that of males. (B605.6.w6)
  • Longevity of more than two years has been recorded for captive, wild-caught Pygmy rabbits, even with limited access to big sagebrush. (B430.w2)
  • Captive Pygmy rabbits are somewhat fragile, and may suddenly die following a dramatic decrease in body weight. (B430.w2)

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Natural Diet

Notes

NATURAL DIET:

Specific Brachylagus idahoensis Information

  • Dietary specialists. (B430.w2)

  • "Pygmy rabbits feed primarily on big sagebrush (Artemisia tridentata), sometimes even climbing into the tops of the larger plants." (B605.6.w6)

  • Even when other shrubs are available, big sagebrush is selected. (B605.6.w6)

  • Diet varies between seasons, with big sagebrush (Artemisia tridentata) comprising up to 99% of their winter diet, and grasses (Agropyron spp. and Poa spp.) constituting 30-40% of their diet in summer. (B605.6.w6, J469.125.w1)

  • Sagebrush Artemisia tridentata is an important component of the diet, making up about 50% of the diet in summer abd up to 99% of the winter diet. They appear more able than are Sylvilagus floridanus - Eastern cottontail to tolerate the terpenes and other chemicals found in sagebrush. (J537.32.w1)

  • Big sagebrush is the main food source for Pygmy rabbits, but grasses are also eaten during the summer. (B147)

QUANTITY EATEN: --

STUDY METHODS: --

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Hibernation / Aestivation

Notes --

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Haematology / Biochemistry

Notes

HAEMATOLOGY:

  • --

BIOCHEMISTRY:

  • --

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Detailed Physiology Notes
(Summary information provided for pertinent species-specific data cross-referenced in Wildpro)

Notes

METABOLISM (TEMPERATURE):

Specific Brachylagus idahoensis Information

  • The energy requirement is relatively high - 750.8 kJ digestible energy/kg0.75 per day while in small cages. Nitrogen requirement was measured at 306.5 mg N per kg0.75 per day. (J537.32.w1)

  • They are more able than expected to digest the fibre found in sagebrush (Artemesia tridentata), an important component of the diet. (J537.32.w1)

RESPIRATORY SYSTEM (RESPIRATION): --

CIRCULATORY SYSTEM (PULSE/HEART RATE): --

GASTROINTESTINAL SYSTEM (FAECES AND GUT MOTILITY): 

General Information

  • Lagomorphs have digestive systems which are adapted for processing large quantities of vegetation. (B285.w5a)
  • Lagomorphs are well adapted for obtaining the greatest possible value from their food. They produce two types of faecal material: moist pellets and dry pellets. The moist pellets are expelled and then eaten (a behaviour known as coprophagy (B285.w5a)); this is done with little or no chewing, and as a result the majority of the food passes through the digestive tract twice (this is thought to have the same function as 'chewing the cud' in ruminants). The dry faecal pellets are not eaten. (B147)

Specific Brachylagus idahoensis Information

  • Pellet groups mean 67.8 faecal pellets per group, and average 12.8 such groups produced per day. (J469.125.w1)

URINARY SYSTEM (URINE): --

CHROMOSOMES: --

MUSCULO-SKELETAL SYSTEM: --

SPECIAL SENSES AND VOCALISATIONS:

General Information

  • All lagomorphs use scent products secreted from special glands (B285.w5a). These glands are located under the chin and in the groin, and are believed to play a key role in sexual communication, as well as in signalling social status in some gregarious species. (B285.w5b)
  • Whereas pikas tend to be more vocal, rabbits and hares rely strongly on scent rather than sound as a means of communication. (B285.w5b)
  • High-pitched distress squeals are emitted by leporids when captured by a predator, and specific alarm calls are produced in five rabbit species. (B285.w5b, B430.w2)
  • Some rabbit species thump the ground with their hind feet when faced with danger (B285.w5b, B430.w2); this reaction is thought to be a warning to nestlings underground. (B285.w5b)
  • The North American leporids have large ears with highly-developed hearing, an adaptation which allows them to detect predators when foraging in open habitats. (B430.w2)

Specific Brachylagus idahoensis Information

  • The Pygmy rabbit alarm call has been described as "a buzzing, one- to seven-syllable squeal." This call has been reported to have been made from within the burrow, as well as when the rabbit is fleeing from the predator. (B430.w2)
  • Pygmy rabbits have several vocalisations, one of which has been described as pika-like. (B147)
  • Loud squeal used when captured - similar to other lagomorphs. "Pika-like" calls have also been reported and have been described as an alarm call. Other identified vocalisations are a chuckle and a squeak. (J469.125.w1)

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Behaviour

Feeding Behaviour

Notes

General Information
  • Lagomorphs are well adapted for obtaining the greatest possible value from their food. They produce two types of faecal material: moist pellets and dry pellets. The moist pellets are expelled and then eaten; this is done with little or no chewing, and as a result the majority of the food passes through the digestive tract twice (this is thought toe have the same function as 'chewing the cud' in ruminants). The dry faecal pellets are not eaten. (B147)

Specific Brachylagus idahoensis Information

  • Pygmy rabbits have been known to feed within the upper canopies of sagebrush stands. (B430.w2)
  • Climb to the top of sagebrush plants to feed on them. (J469.125.w1)
  • If the winter snow covers the sagebrush, Pygmy rabbits may create extensive burrows within the snow, in order to provide them with access to the sagebrush canopy. (B430.w2)
  • The feeding activity of Pygmy rabbits near their burrow sites may, in itself, encourage an increase in sagebrush density, thus Pygmy rabbits may be somewhat self-sustaining. (B605.6.w6)

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Parental Behaviour

Notes

General Information

  • Male leporids are not generally involved in care of the young. However, if adult females attack young leporids, males will intervene, a behaviour known as 'policing'. (B285.w5b)
  • Even maternal care of the young is not particularly prominent in leporids, hence this reproductive strategy is known as 'absentee parentism'. (B285.w5a)
  • Leporids demonstrate an unusual system of nursing; the young are suckled only briefly (often less than five minutes) just once every 24 hours. (B285.w5b)
  • It is thought that the lack of social contact between the mother and her young is a strategy which diminishes the chances of attracting the attention of predators. (B285.w5b)
  • The entrances to breeding tunnels are carefully re-sealed following each bout of suckling. (B285.w5b)

Specific Brachylagus idahoensis Information

  • Starting 12.8 +/- 2.8 days after copulation the female begins digging a natal burrow. This is usually (38/45 observed) a separate burrow from the main burrow system but on seven occasions was a side chamber off an existing burrow. Natal burrows were 16.5 - 35.5 cm long; it was not known whether this length was constrained by the captive conditions. Burrows were dug in one to three days and covered either at the end of each digging session or only when completed. After the burrow is completed, the female drags nesting material (e.g. hay in captivity) into the burrow to build a nest. The burrow was completed 7.3 +/- 2.2 days before parturition. Shortly before parturition, the nest was lined with fur plucked from the abdomen, sides, back and flanks of the female. (J332.87.w1)
  • In captivity, immediately after birth, newborns could sometimes be seen moving around the burrow entrance (birth typically took place at the burrow entrance); they either crawled into the burrow or the doe carried them in, then the doe covered the burrow entrance with soil and hay/twigs. Sometimes females were seen to carry dead kits out of the burrow (other times the female merely left the burrow open after kits died, ceasing maternal behaviour). (J332.87.w1)
  • For nursing, once (six of eight litters) or twice (two of eight litters) a day, the female opened up the natal burrow (taking 2.4 +/- 1.4 minutes) and the young usually came to the surface of the burrow; sometimes the female would bring young to the burrow entrance and occasionally the female would enter the burrow and nurse the young there. Usually the female hunched over the burrow or sat on her hind legs with "front paws resting over the natal burrow and their abdomens covering the burrow entrance." The female would clean the young while they lay on their back and sides and nursed. Nursing generally occured 1900 - 2400 hr or 0500 - 1100hr. On average, the female would nurse her young for 10.6 +/- 2.7 minutes; the average was longer for females nursing young once a day than for those nursing twice a day (11.1 +/- 0.3 versus 9.8 +/- 0.4 minutes (mean +/- SE). Following nursing, either the young crawled back into the burrow or the female carried them back in. At about 15 days the female no longer re-covers the nest after nursing her young. From this time, young generally initiate nursing and the female often starts to become intolerant of this, chasing and biting the young; nursing was not seen more than two weeks after emergence. (J332.87.w1)

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Social Behaviour / Territoriality / Predation / Learning

Notes

SOCIAL BEHAVIOUR:

General Information

  • Most North American leporid species are solitary, but congregations of these animals often occur in favoured feeding grounds. (B430.w2)
  • Rabbits are solitary to gregarious. (B430.w2)

Specific Brachylagus idahoensis Information

  • "The population dynamics of the pygmy rabbit are not well understood". (B605.6.w6)
  • The expression of alarm calls by the Pygmy rabbit suggests that some form of sociality is present in this species, which is not present in other North American leporids. (B430.w2)
  • Usually one per burrow, but several may use the same burrow when frightened. (J469.125.w1)
  • Have been found in the same burrow system as Sylvilagus nuttallii - Mountain cottontail. (J469.125.w1)

PREDATION:

Specific Brachylagus idahoensis Information

PREDATOR AVOIDANCE:

General Information

  • Rabbits use dense cover to hide from predators. (B285.w5b)

POPULATION DENSITIES:

Specific Brachylagus idahoensis Information

  • Widely varied population density estimates have been made for this species, with estimates ranging from as low as 0.7-1.4 Pygmy rabbits per hectare in one study, up to 45 individuals per hectare in a study conducted in ideal habitat. (B147, B430.w2, B605.6.w6, J469.125.w1)
  • Conflicting opinions exist as to whether or not this species exhibits population cycling. (B430.w2, B605.6.w6)

HOME RANGES AND DISTANCES TRAVELLED:

Specific Brachylagus idahoensis Information

  • "The home range size of the pygmy rabbit has never been determined". (B605.6.w6)
  • Feeding activity generally occurs within a 30 m radius of the burrow during the winter, a distance which subsequently increases in the spring and summer. (B147, B605.6.w6, J469.125.w1)
  • One set of tracks has been followed for a distance of 250 m, and in another instance an escaped captive Pygmy rabbit was found to have returned to its burrow of origin located 2.6 km away from its holding pen. (B605.6.w6)
  • Sagebrush occurring in riparian areas alongside streams can provide a means for dispersal between larger areas of sagebrush. (B605.6.w6)
  • Extensive runways often cross the sage thickets (B285.w5c) which act as travel and escape paths for the rabbits. (B147)

TERRITORIALITY:

General Information

  • The majority of hares and rabbits are non-territorial, and ranges of individuals may overlap in favoured feeding grounds. (B285.w5b)

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Sexual Behaviour

Notes

General Information

  • All lagomorphs use scent products secreted from special glands. (B285.w5a) These glands are located under the chin and in the groin, and are believed to play a key role in sexual communication, as well as in signalling social status in some gregarious species. (B285.w5b)

Specific Brachylagus idahoensis Information

  • Mating behaviour observed in captivity included mainly chasing be either the male or female, followed by a brief (less than one second) copulation involving a single pelvic thrust. Chasing lasted anything from 16 seconds to 175.7 minutes. During chasing, behaviours such as biting and boxing were seen; the male would copulate either while chasing the female or when she stopped for a moment, allowing the male to mount. there were one to eight copulations per breeding session, but usually (87.5% of sessions) more than one copulation. Following copulation 0.9 - 73.7 minutes was spent chasing, often with the female acting aggressively - scratching, boxing or wrestling - or ignoring the male. (J332.87.w1)

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Activity Patterns, Self-grooming and Navigation

Notes

ACTIVITY PATTERNS:

Specific Brachylagus idahoensis Information

  • During the summer months Pygmy rabbits use their burrows in order to keep cool, and also rest outside the burrow. (B430.w2)
  • During the winter months, Pygmy rabbits frequently sun themselves near a burrow in the late morning and early evening. (B430.w2)
  • "They have a rather deliberate gait, staying low to the ground. To avoid predators, they may depend more on their ability to maneuver through dense sagebrush than on speed." (B605.6.w6)
  • Pygmy rabbits do not leap, but rather move in a low scampering gait. (B147, B430.w2, J469.125.w1)
  • Pygmy rabbits have been described as having scurrying movements. (B430.w2)
  • Climb to the top of sagebrush plants to feed on them. (J469.125.w1)
  • Usually stay within about 30 m of the burrow in winter, but move further in spring and summer. (J469.125.w1)

SELF-GROOMING: --

CIRCADIAN RHYTHM: 

Specific Brachylagus idahoensis Information

  • "This species is reported to be crepuscular, but may be found above ground any time of day." (B605.6.w6)
  • Peak activity in a study in Idaho was found to be during mid-morning. (B605.6.w6)
  • Generally considered to be crepuscular, but may be active at any time. (B147, B430.w2, J469.125.w1)
  • Rest in forms under vegetation during the day. (J469.125.w1)
  • Usually rest in or neer burrows during the day, but have been seen feeding at midday. (J469.125.w1)

SPEED OF MOVEMENT:

General Information

  • The North American leporids are able to escape predators by taking instant flight at high speed. (B430.w2)

Specific Brachylagus idahoensis Information

  • May travel at 15 mph (24 km/h). (J469.125.w1)

NAVIGATION:

Specific Brachylagus idahoensis Information

  • For one juvenile, homing reported from a 2.5 km displacement. (J469.125.w1)

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Habitat and Range

General Habitat Type

Notes

Specific Brachylagus idahoensis Information

  • Habitat specialists. (B430.w2)
  • Steppe and scrub. (B51)
  • Mainly dependent upon very dense stands of sagebrush (largely big sagebrush Artemisia tridentata) (B147, B285.w5c, B430.w2, J469.125.w1), as well as bitterbrush (Purshia tridentata). Within these stands, sites which have the greatest cover densities are chosen by this species. Tall sagebrush clumps are thought to be essential for Pygmy rabbits. (B605.6.w6)
  • Pygmy rabbits are also found "on plains, alluvial fans, riparian gullies, and in fenced right-of-ways along roads." (B430.w2)
  • A study in Idaho found that whilst the mean shrub height of the area was 25 cm, the mean shrub height for sites chosen by Pygmy rabbits was 56 cm. A study in Oregon found a similar pattern, with mean shrub height at sites selected by Pygmy rabbits being 84 cm, compared with 53 cm at unoccupied sites. (B605.6.w6)
  • High cover density appears to be a major factor in habitat selection by this species. (B605.6.w6)
  • "The density of big sagebrush in areas used by pygmy rabbits exceeds that which is found throughout most of the plant's distribution." Such dense areas often occur as a result of past disturbance from grazing or cultivation, with big sagebrush rarely being the dominant plant in undisturbed areas. (B605.6.w6)
  • Riverine scrub can provide corridors through which dispersal can occur. (B605.6.w6)
  • Due to the fact that the Pygmy rabbit provides burrows for other animals to utilise, acts as a food source for both terrestrial and avian predators, and does not thrive in habitat types of differing vegetation dominance, it is considered to be a keystone species in its big sagebrush habitat. (B430.w2)

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Nests / Burrows / Shelters

Notes

General Information
  • Rabbits tend to live in burrows or in surface nests which are joined by clear trails. (B430.w2)

Specific Brachylagus idahoensis Information

  • Use burrows. (J469.125.w1)
  • "The burrowing habit of the pygmy rabbit is unique among the western North American rabbits". (B605.6.w6)
  • The majority of burrows are located under big sagebrush (Artemisia tridentata), with very few being located in an opening in the vegetation. (B605.6.w6)
  • These rabbits dig their own burrows, unlike the other North American leporids. Burrows typically have four or five entrances but as many as ten have been reported. (B147, B605.6.w6, J469.125.w1) Burrows in Idaho generally had two entrances. (B605.6.w6)
  • Soil structure (generally soft and deep) is thought to be a key habitat feature for this species (such as in areas where wind-borne soil deposits are deeper), as it makes its own burrows. A study in Oregon found that burrow sites were located in areas where soil was significantly looser and deeper than in areas adjacent to burrow sites. (B605.6.w6)
  • This species has also been found to make use of holes found in volcanic rock, rock piles and around deserted buildings. "Usually these cases are in association with a population using typical deep soil, sagebrush burrow sites and may only be an energy-efficient alternative to digging a burrow, or may give added protection against predators that excavate the burrows" . (B605.6.w6)
  • Burrow site selection also relies upon topography; the contours of the soil are used, and Pygmy rabbits usually dig into a slope (B147, B605.6.w6, J469.125.w1). When creating a burrow at a level site, the burrow entrance is often made by utilising a small change in contour. (B605.6.w6)
  • Burrows are usually oriented north to east. (J469.125.w1)
  • Entrances are 10-12 cm in diameter and usually found at the base of a large sagebrush on a gentle slope. (B605.6.w6, J469.125.w1)
  • Tunnels usually extend to no more than one metre in depth." (B605.6.w6)
  • Tunnels widen into chambers below the surface, and extend no further than about one metre in depth. (B147, B605.6.w, J469.125.w1).
  • The pygmy rabbit usually constructs its own burrow (B147, B285.w5b, B285.w5c, B605.6.w6) but also takes advantage of holes in rocks, as well as occupying burrows made by other animals such as Taxidea taxus (Mustelidae - Weasels (Family)) and Marmota flaviventris (Marmota - (Genus)). (B147, J469.125.w1)
  • Usually, only one individual occupies any given burrow, but reports have been made of pairs being found together in burrows during the breeding season, and it is thought that, if frightened, several animals may take shelter in the same burrow. (B147)
  • If the winter snow covers the sagebrush, pygmy rabbits may create extensive burrows within the snow, in order to provide them with access to the sagebrush canopy. In such instances, they may not even have a burrow entrance at the surface of the snow. (B430.w2)
  • Complexity of burrow systems varies greatly. (B430.w2)
  • "Although pygmy rabbits are unique among North American leporids in their construction of burrows, no nesting chambers have been found in the few burrows excavated." (B430.w2)
  • During the day, forms under vegetation are used for resting. (J469.125.w1)
  • In winter, make subnivean trail networks at the bases of large sagebrushes, providing larger areas for feeding; the burrows sometimes but not always extend to the snow surface. (J469.125.w1)
  • Natal burrows:
    • Information from rabbits in pens with 0.5 - 1 m deep soil substrate: starting 12.8 +/- 2.8 days after copulation the female begins digging a natal burrow. This is usually (38/45 observed) a separate burrow from the main burrow system but on seven occasions was a side chamber off an existing burrow. Natal burrows were 16.5 - 35.5 cm long; it was not known whether this length was constrained by the captive conditions. Burrows were dug in one to three days and covered either at the end of each digging session or only when completed. After the burrow is completed, the female drags nesting material (e.g. grass and hay in captivity) into the burrow to build a nest. The burrow was completed 7.3 +/- 2.2 days before parturition. Shortly before parturition, the nest was lined with fur plucked from the abdomen, sides, back and flanks of the female. (J332.87.w1)
    • Note: the entrance to a natal burrow is camouflaged so well it cannot be located even within a pen of a captive rabbit. (J536.65.w1)
    • In free-living rabbits, natal burrows were observed being dug and then back-file at 1030 and 0815 hours. Six completed natal burrows which were found were 17 - 30 cm long, ending in a single spherical chamber, and contained nesting material including hair, fine grasses and shredded sagebush (Artemisia spp.) bark in the nest chamber. Three of the burrows were well away (more than 50 m) from active/recently active residential burrow systems, while the others were 8 - 44 m away; overall, burrows averaged more than 35 m from active burrows. Six natal burrows were associated with mima mounds, with five having the entrance under sagebrush and the sixth under rabbitbush; average shrub height aroung the burrows on mima mounds was 59.7 cm (41 - 86 cm). The seventh burrow opening was between mounds, under a weathered stump of sagebrush. (J536.65.w1)

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Distribution and Movement (Migration etc.)

Notes

North America:

  • Southwest Oregon to east-central California, southwest Utah, north to southwest Montana (USA). Isolated populations in west-central Washington State (USA). (B285.w5c, B607.w20)
  • "S. idahoensis [Brachylagus idahoensis] is found in southeastern Washington, eastern Oregon, southern Idaho, southwestern Montana, southwestern Wyoming, northeastern California, northern Nevada, and western Utah." (B147)
  • Recently, the Pygmy rabbit has extended its range to include north- and southeastern Utah. (B430.w2)
  • "The eastern boundary extends to southwestern Montana and western Wyoming. The southeastern boundary extends to southwestern Utah and includes the only occurrence of the species outside the limits of the Pleistocene Lake Bonnewille (Columbia River) drainage. Central Nevada and northeastern California form the southern and western boundaries. The northern boundary of the main population historically reached to the southern foothills of the Blue Mountain Plateau in eastern Oregon." (B605.6.w6)
  • Douglas County Washington forms the northernmost part of its range. (B605.6.w6)
  • The distribution has been reported to have shrunk southward toward central eastern Oregon. (B605.6.w6)
  • Found in Montana, Idaho and Oregon. (B51)
  • Occurrence within its range is not continuous, with the species demonstrating a preference for denser sagebrush/bitterbrush habitat. (B605.6.w6)
  • The population in Washington is isolated from the rest of the range of the species, a fact which, combined with habitat change, is thought to account for the decline in numbers of this species since its postglacial population high 7,000 years ago. (B605.6.w6)
  • Historically had a larger range, but this has since been reduced due to the removal of much of the sagebrush habitat for agricultural purposes. (B430.w2, B605.6.w6)
  • Fires in extensive sagebrush stands have also had a negative effect on Pygmy rabbit populations. (B430.w2)
  • Evidence suggests that only one population remains in Washington state (B605.6.w6)
Geographic sympatry

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Conservation

Species variation

Notes

Specific Brachylagus idahoensis Information

  • This species was formerly included in Sylvilagus. (B607.w20)
  • Brachylagus is often counted as a subgenus of Sylvilagus, but based on information including serological, morphological and behavioural data, is considered to be generically distinct. (B147)
  • Note: monotypic genus and no apparent subspecies. (J469.125.w1)

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Conservation Status

Notes

WILD POPULATION - IMPORTANCE:

  • "The status of the pygmy rabbit varies widely, from secure populations in large expanses of sagebrush such as occur in Idaho, to isolated remnants in Washington." (B605.6.w6)
  • This species is quite vulnerable due to its dependency upon big sagebrush (Artemisia tridentata), combined with reductions in shrub cover due to human activity. (B605.6.w6)
  • Habitat fragmentation is a key threat to this species. (B430.w2)
  • Some populations remain isolated due to limited immigration as a result of reluctance to traverse even moderately large areas of open land. (B605.6.w6)
  • Spontaneous local extinctions of these isolated populations can occur as a result of both genetic drift and stochastic events including fire or disease outbreaks. The smaller the isolated area, the greater the chance of such a local extinction occurring. This is particularly true of the populations on the fringes of the range. (B605.6.w6)
  • Rapid population declines may be occurring in Oregon; when 15 active sites were sampled in two consecutive years, ten of these sites were no longer active in the second year. (B605.6.w6)
  • "When declines occur in isolated populations, extinctions are likely. These extinctions are cumulative, progressively reducing the extent of the species' range." (B605.6.w6)
  • The protection and/or creation of corridors of sagebrush along riparian areas near streams could be applied as a useful and effective management tool in order to assist the in the dispersal, and hence mixing, of populations. (B605.6.w6)
  • Note: In Washington State, in the period 1995 - 2001, five of the six populations disappeared, so that by March 2001 only one population, at Sagebush Flats, near Ephrata, remained; this population showed a dramatic decline in the winter of 2000 - 2001, for unknown reasons. (D372 - The Columbia Basin Pygmy Rabbit Captive Breeding and Genetic Management Plan (full text included)

GENERAL LEGISLATION: 

  • U.S. Endangered Species Act (ESA) - isolated population in Washington (Columbia River Basin) considered endangered. (B607.w20)

CITES LISTING: --

RED-DATA LIST STATUS:

  • IUCN - Lower Risk (near threatened). (W2.Apr08.w1)

THREATS:

  • Overgrazing, in the short-term, leads to a reduction in the availability of summer grass and forb forage for the Pygmy rabbits. Continued overgrazing over several successive seasons can have severe impacts upon the resident rabbit population, and this population can only be restocked once overgrazing ceases, through immigration from neighbouring habitats. This cannot, however, be achieved in the case of isolated populations. (B605.6.w6)
  • Cattle can cause damage to the structure of areas of sagebrush. (B605.6.w6)
  • Thought to be vulnerable due to its complete dependence on the presence of big sagebrush, and the destruction of much of its habitat through agricultural use and grazing. (B147)

PEST STATUS / PEST POPULATIONS:

  • Some leporids are agricultural pests. (B430.w2)
  • Populations which have been introduced to sites from other areas often become the biggest pests. (B430.w2)

CAPTIVE POPULATIONS:

TRADE AND USE: --

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