Pygmy Rabbits by Daniel Dempster

The pygmy rabbit (Brachylagus idahoensis) is the smallest species of rabbit in North America, found mostly in the northwestern states of the USA. Its geographic range is mostly contiguous through the state of California, Nevada, Oregon, Idaho, Utah, and Wyoming, but has a secluded permanent residence in eastern Washington. It is in this distinct population segment in the Columbia Basin where the species has been listed under the EPA as endangered. It was listed in November of 2001

The herbivorous pygmy rabbit tends to reside in shrubland areas, using dense stands of big sagebrush growing in loose soils. Sagebrush is used by these rabbits for food and shelter throughout the year. Pygmy rabbits are unusual from other rabbits in that they are one of only two species of rabbits in North America that burrow, which is why they look for loose soil. The burrows have multiple uses, creating shelter near food sources (sagebrush), thermal protection, and protection from predators. Predators of the pygmy rabbit include weasels, coyotes, owls, and many other carnivorous mammals and birds. While sagebrush remains the primary source of the pygmy rabbit’s food, especially in winter, grass and forbs provide for food in the spring as well.

Pygmy Rabbits in their burrows

The pygmy rabbit is a very localized and non-migrant species, which could probably be attributed to its lack of size and mobility. Another large contributing factor to their localization is that they like to stay close to their food sources, especially in winter when sagebrush is likely the only option for food. However, the home range estimates in the state of Washington, where the pygmy rabbit is listed, are considerably larger that estimates in other portions.

Note the secluded section in Washington

There have been observations of rapid local declines of populations in several states, especially in Washington. Annual mortality rates with adults in the population have been recorded as high as 88%, along with juvenile mortality rates being over 50% within 5 weeks of birth. This mortality rate is probably best explained by predation, yet starvation and environmental stress can also be serious factors. Pygmy rabbits were considered rare in the 20th century, and were thought to be extirpated from Washington until their rediscovery in 1979. With surveys conducted in 1987 and 1988, 5 subpopulations were found in Washington which were very small as four of the five had populations of under 100. Another subpopulation was found in 1997, but five of the total six were found to be extirpated in 2001. One of the extirpated spots experienced a fire, wiping out much of the necessities for the rabbits.

The likely primary threat to the pygmy rabbits is habitat loss and fragmentation. Nearly 60% of the original native shrub steppe habitats that house them have been lost to dryland and irrigated crop production, urban/rural development, and fires. While this is the probable primary threat, many other threats linger as the populations drop below a certain threshold. These secondary threats include disease, predation, loss of genetic diversity, and inbreed depression.

The recovery plan outlines specific short-term objectives (2012-2021) and and overall long term goal. In the short term, the objectives include implementing the Reintroduction and Genetic Management Plan and revise it as necessary, having these reintroduced rabbit subpopulations retain characteristics of Columbia Basin specific ancestry and be considered fit by veterinary staff. In hopes that this initial reintroduction is successful, a sufficient number and demographic composition of pygmy rabbits need to be retained in order to support partially controlled field-breeding. Thereafter, two specific recovery emphasis areas need to have a subpopulation with a 5-year average of 125 individuals, approximating the last known subpopulation in the Sagebrush Flat site. To ensure this objective is meet, estimators need to be updated as necessary. Later in the short term, more recovery emphasis areas will need to be established. The final short term objective is to make conservation agreements with landowners, managers, and other interested populations within the historical distribution of the Columbia Basin pygmy rabbit. The long term objective is to increase the size, number, distribution, and security of free-ranging subpopulations of the Columbia Basin pygmy rabbit.

Other Links:

http://www.westernwatersheds.org/issues/species/pygmy-rabbits/

http://www.fws.gov/nevada/nv_species/pygmy_rabbit.html

http://www.oregonzoo.org/conserve/species-recovery-and-conservation/columbia-basin-pygmy-rabbits