Everything you need to know about the Columbia Basin Pygmy Rabbit

Columbia Basin Distinct Population Segment of Pygmy Rabbit (Brachylagus idahoensis)

Blogger: Dana Shell

 

The Columbia Basin Population Segment of Pygmy Rabbit is currently listed as ENDANGERED as of 11/30/2001

Lead region: Pacific Reion (Region 1)

Where listed: USA (WA-Douglas, Grant, Lincoln, Adams, Benton Counties)

 

Video of Pygmy rabbit in reintroduction enclosure

 

What does the species look like…

Part of the Leporidae family, the pygmy rabbit is within the monotypic genus Brachylagus classified as B idahonesis. With a weight range of .83-1.1 pounds and a length range of 23.5 to 29.5, the pygmy rabbit is the smallest leporid in North America. They undergo an annual molt. Their legs, chest, and nape are tawny cinnamon brown, bellies are whitish. Their short, thickly furred, rounded ears are pale bluff. They have very small tails, uniform in color. Distinguishing characteristics of this species are: its small size, short ears, gray color, small hind legs, and lack of white on tail.

 

What do the habitats of these cute rabbits look like?

The historical habitat for the pygmy rabbit include the majority of the semiarid shrub steppe biome of the Great Basin and of adjacent regions of the wester US. Pygmy rabbits are not currently distributed across their range, nor were they in the past. Instead they are distributed where suitable habitats occur that are comprised of dense vegetation among permanent and intermittent stream channels, alluvial fans, and sagebrush plains. Their distribution shifts across these patches in response to disturbance (fire, flood, grazing, crop production) and weather patterns.

This distinct segment of pygmy rabbit, historically distributed in Columbia Basin, has been disjoint from the remainder of the species for 10,000-7,000 years. Global climate change has affected the once broad range of this species habitat composition. The species historically lied with in the big sagebrush—blue wheatgrass. The habitat is comprised of four well-defined layers. The first layer (the most pertinent) consists of various shrub species, principally big sage brush that are intermixed with second layer comprised of a variety of tall perennial grasses. The third layer consists of low lying perennial and annual grasses and forbs. The final layer is made up of thin, fragile cryptogamic crust, occurring on the surface of the soil. The fourth layer is comprised of carious lichen, moss, and liverwort species, that greatly affect how susceptible to erosion, moisture retention, and nutrient cycling. Pygmy rabbits are most likely to be found in areas that include the tallest grass and areas that are the densest. The sagebrush is extremely critical to this species, as it is a main source of food and shelter.

 

Species range:

Pygmy rabbit’s Life History

During the winter season, the range of this species is within 30 meters of their small burrow—some snow burrows extending an additional 100 meters. During the spring and summer their ranges increase greatly. Females –who are generally larger than the males-- tend to make small movements in a core area during breeding season. Males make larger movements, most likely seeking out . Juveniles often undertake a single rapid dispersal movement in the first 6-10 weeks. These rabbits are particularly vulnerable with their low stance, deliberate gait, when in open areas. The ability to maneuver through dense vegetation, and hide in their burrows are their main defenses against predators.

 

Let’s talk about Burrows…

The pygmy rabbit is one of two in its species that its own burrows. These burrows are generally dug out of slopes or mounds that a made up of relatively deep, loose soil. Alternatively, the rabbits may burrow in areas of shallower, sandy soils that support sufficient shrub cover. Extensive burrows are dug in the winter in order to access sagebrush forage. The relatively simple and shallow burrows (1-2 meters) tend to have multiple entrances, some concealed by plants or vegetation. The number of burrows will increase during the summer season, however, do not reflect the population. Pygmy rabbits may maintain several burrows at a time.

 

What do they like to eat?

Their winter diet mainly consists of sagebrush. During the spring/summer they like to ass other native bunch grasses, and a small portion of forbs to their diet.

 

 

Breeding:

 This r-selected species begins breeding about a year after birth between January and June. Females may have 1-4 litters a year with a gestation that lasts 22-24 days. Their offspring (called kits) leave their  “natal” burrows at about two weeks old for the first time. These “natal” burrows generally have a single entrance covered by sagebrush.

 

Mortality rates L

The average mortality rate for adults may e as high as 88%, up to 50% of juvinilles dying in the first 5 weeks. Causes of mortality include: starvation and environmental stress, and predation a main threat. Predators of the pygmy rabbit are: badgers, long-tailed weasels, coyotes, and bobcats, and horned owls, hawks, and common ravens.

 

Geographic and population trends:

During the Early 20^th century the species was considered rare, thought to be extirpated from Washington during mid-20^th century until a sighting in 1979. From 1987-1988: Five small subpopulations were found on state lands, 2 on private lands. The Columbia Basin pygmy rabbit only have been found in southern Douglas and the norther Grant Counties.

 

The species population declined after their rediscovery in the 1980s. Four out of five of their populations contained less than 100 active burrows. (remember that pygmy rabbits may keep multiple burrows at a time). The fifth population was estimated, in 1993, to have almost 600 active burrows supporting fewer than 150 pygmy rabbits. An additional subpopulation was found on private lands in 1997.

 

By 2001 5/6 subpopulations were extirpated leaving a single known subpopulation at the Sagebrush Flat site. Unfortunately, the number of active burrows decreased by 50% in 1997 and continued to decline. No animals from this subpopulation have been detected since before 2004, meaning the Columbia pygmy rabbit may have been completely extirpated from the wild. There is only about7.7 % of suitable habitat (shrub) that remains within the Columbia Basin.

 

Fall 2000, captive breeding and reintroduction programs were started by the WDFW. The first 10 breeding seasons yielded a 25% annual growth, increasing over time from a low 19 to high of 275. Upon release, none survived beyond spring 2008 and efforts were put on pause. Reintroduction efforts were resumed in 2011, where several series of captive bred kits were released in the Columbia Basin. By 2012, there were a successful 103 captive breeds released into the site.

 

 

 

 

Main Threats to continued Existence

Five factors identified in sec 4(a)(1) of the ESA consideration for listing:

1 The present or threatened destruction, modification, or curtailment of its habitat or range

60% of native shrub steppe habitats in the Columbia Basin have been converted to either land for crop production or completely destroyed by urban and rural developments. Other causes the shrub habitats include: fires, invasive plant species, recreation and livestock grazing.

 

2 Overutilization for commercial, recreational, scientific, or educational purposes

 

Due to the difficulty to distinguish between species of rabbits, the pygmy rabbit is subject to accidental shooting. Use of hunting dogs may add additional risk of harm or harassment. Trapping, handling and translocation can also lead to mortality, the primary causes being: injury from trap, intra specific fighting, and capture stress. The rabbits shallow burrows are also very susceptible to harm via human interaction (accidently stepping on one may destroy it).

 

3 Disease and Predation

The high parasite load that the pygmy rabbits carry (ticks, fleas, and lice) are often vectors of disease. Plaque and tularemia have been reported, as well as, several disease epidemics. Coccidiosis, a disease caused by protozoan occurring in soil/fences, is very detrimental to the rabbits. Bacteria from soil and water also infects these rabbits who have very poor immune systems. Inbreeding has also resulted in skeletal abnormalities, decreasing genetic diversity. Predation is thought to be a huge cause of mortality among the rabbits. With a good distribution, it is not likely to be a long term threat.

 

4 The inadequacy of existing regulatory mechanisms

Beyond the endangered species act, Washington does not provide regulatory information that prohibits activities that may incidentally harm the species.

 

5 Other natural or human-caused factors affecting its continued existence

 

Small populations are very susceptible to random environmental events, abrupt changes in food or shelter, disease outbreaks, predators, and genetic limitations. Inbreeding depression and poor reproductive performance was observed in both the wild and captive populations.

 

Recovery Plan

 

The three phase recovery plan consists of:

1. removal or abatement of imminent threats to the population and suitable shrub steppe habitats in the Columbia Basin

2. the reestablishment of an appropriate number and distribution of free ranging subpopulations over the near term

3.establishment and protection of a sufficiently resilient, free ranging population that would be expected to withstand foreseeable long term threats

 

The outline of Recovery actions are listed below:

1. Manage partially controlled field-breeding for the CBPR
2. Reestablish free-ranging CBPR subpopulations within their historical distribution
3. Survey for, monitor, and asses free-ranging CBPR
4. Protect free-ranging CBPR
5. Manage habitats at recovery emphasis areas and intervening properties
6. Pursue Conservation agreements with landowners and managers of intervening properties within the population's historical distribution
7. Exchange info w/ stakeholders and the general public to address concerns and increase support for CBPR recovery efforts
8. Secure funding for CBPR Recovery efforts
9. Revise this Federal Recovery Plan to facilitate implementation of adaptive management measures considered necessary to achieve the phased recovery strategy

 

To read more in depth about the recovery plan and efforts please visit the link below:

 

Columbia Basin Pygmy Rabbit Recovery Plan