Published: April 2003
Author(s): David W. Hays
This document summarizes 2002 recovery efforts for the Columbia Basin pygmy rabbit, and outlines new tasks to be completed in 2003. The initial (1995)Washington State Recovery Plan for the Pygmy Rabbit was updated with the 2001 Addendum, Emergency Measures for Species Survival.This is the second addendum to the 1995 recovery plan.
The pygmy rabbit was listed as a threatened species in the state in 1990 and was reclassified to endangered status in 1993. It was listed under emergency provisions of the federal Endangered Species Act in November 2001 by the U.S. Fish and Wildlife Service, with a final rule continuing the endangered listing in March 2003. A state recovery plan for the rabbit was written in 1995. Recovery objectives are to increase pygmy rabbit numbers and distribution and manage habitat for long-term protection of features that support pygmy rabbits.
Less than 30 Columbia Basin pygmy rabbits are believed to remain in the wild. A captive breeding program was initiated in 2001. The captive breeding program is a cooperative project involving the WDFW (lead agency), and Washington State University, the Oregon Zoo, and Northwest Trek Wildlife Park, where captive breeding occurs.
The 2002 breeding season was the first breeding season for Columbia Basin pygmy rabbits. Eighteen rabbits were paired beginning in early March, but breeding did not occur until mid-April. The first litters were born between May 1 and 3. Of 12 different pairings at Washington State University, only two produced young. One of the pairs produced stillborn young and the other pair produced 5 young. One re-pairing later in the spring produced only stillborn young. At the Oregon Zoo, eight pairings were attempted with only two pairings producing a total of 10 young. Re-matings were not successful, with one re-mating producing two stillborn young. A total of fifteen young Columbia Basin pygmy rabbits were born in 2002, but disease in the captive population, most notably avian tuberculosis, eliminated numerical gains in the captive population and reduced genetic diversity.
Additional recovery efforts included rearing and releasing captive Idaho pygmy rabbits back into Idaho as an experiment, to test and improving release methods. A total of 20 Idaho pygmy rabbits born in captivity in 2002 were released in two groups at the Idaho National Environmental Engineering Laboratory near Idaho Falls, Idaho. The first group of 13 rabbits was released August 9 and the second group of 7 was released September 16. Four rabbits survived to breeding season 2003. Plans for 2003 are for a similar experiment to further test release methods.
Funds for habitat acquisition were secured in 2003, which could potentially assist in developing a second release site for pygmy rabbits. Surveys conducted during winter 2001-2002 at Sagebrush Flat Wildlife Area located located 23 active burrows in three general areas. Visitation to these three areas during the winter of 2002-2003 found active burrows in one of the three general areas. Surveys of potential habitat continued in 2002 by both WDFW and the Bureau of Land Management, but no new pygmy rabbits were found. Genetic analyses indicate that genetic drift has occurred in the captive population, resulting in a significant decline in genetic diversity. New initiatives for 2003 include conducting experimental cross-breeding of pygmy rabbits from the Columbia Basin with those from Idaho, expanding captive breeding facilities at Northwest Trek Wildlife Park, and developing agreements with private landowners to survey for other pygmy rabbits in the wild.