Pygmy rabbit 'love connection' may advance endangered species breeding programs
Coaxing endangered Columbia Basin pygmy rabbits into "breeding like rabbits" has never been simple. But a recent breakthrough at the Oregon Zoo suggests the secret to rabbit chemistry lies in the right matchmaking service. Now, the mate-compatibility research may prove beneficial for another unlucky-in-love endangered species: the giant panda.
"The panda is the world ambassador for all endangered species," said Meghan Martin, the Oregon Zoo research associate who led the study. "If our research with pandas shows similar findings to what we've seen in pygmy rabbits, it will be a very big deal for the zoo breeding world."
In 2001, the Oregon Zoo had become the first in the world to breed the highly endangered Columbia Basin pygmy rabbits. But like many endangered species breeding programs, the miniscule bunnies were plagued with low birth rates and incompatibility among mates. Animals are typically paired based on estimates of genetic relatedness.
The dilemma prompted a community of animal-care professionals and scientists like Martin, a Portland State University graduate student, to consider whether allowing the animals to choose their own mates might improve reproductive success.
So in the spring of 2010, with a grant from the Oregon Zoo's Future for Wildlife program, Martin and Dr. David Shepherdson, the zoo's deputy director of conservation, organized a rabbit "speed-dating" program. Rabbits were housed in rows of neighboring open-air pens, alternating between male and female, thus giving each female a choice between two males.
"Females are the limiting factor in many breeding programs for mammals, because they tend to be the choosiest," Martin said. "The female rabbits always chose one male over the other, and in most cases, one male was extremely preferred."
Each female's preference was judged by her behavior — whether she rubbed heads with a male through the fencing, chased him or ran parallel with him along the barrier.
Females were then paired with males from one of four categories: neighbor, non-neighbor, preferred and non-preferred.
Less than a month later, the researchers trained their eyes on the rabbit burrows, waiting to see which ones produced kits. As expected, the females that had been paired with neighbors and preferred males were more likely to have litters than those paired with non-neighbors and non-preferred males.
But surprisingly, females paired with neighbors and preferred males also had larger litters — suggesting that familiarity and preference played an even more important role in reproductive success. Another measure of success would be discovered a year later.
"Only two kits born to non-neighbor pairs survived their first year," Martin said. "But of the kits born to neighbors, 20 survived. Females who were familiar with their mates had healthier babies. We had predicted these results, but we were completely surprised by the magnitude of the difference — mate selection made a huge difference for the success of a pairing."
Martin and Shepherdson's study, published last summer in Conservation Biology, concluded the zoo's 12-year effort to save the endangered Columbia Basin pygmy rabbit in collaboration with the Washington Department of Fish and Wildlife, the U.S. Fish and Wildlife Service, Northwest Trek Wildlife Park and Washington State University. In July, the zoo released its last 14 breeding rabbits and their offspring at the Sagebrush Flat Wildlife Area in eastern Washington. Last month, WDFW reported some good news: Pygmy rabbits released in the area had survived the leanest part of the winter.
"Pygmy rabbits probably use a variety of factors to find quality mates, like evaluating jump height and dodging ability," Shepherdson said. "These traits may increase their offspring's odds of survival. We don't know everything animals use to evaluate potential mates, but it might prove best to revert to their natural systems as much as possible and let animals pick for themselves."
This winter, Martin is in China attempting to find breeding success with another, less obscure endangered species.
"Giant pandas are notorious for their reluctance to breed in captivity," Martin said. "Applying the findings from our pygmy rabbit studies to this critically endangered species could be a key to increasing the panda population."
Martin's current research — taking place at the Bifengxia Panda Reserve in Ya'an, China — is being conducted in collaboration with Portland State University, the Zoological Society of San Diego, and the China Conservation and Research Center for Giant Pandas. Martin will expand on her pygmy rabbit study by taking male preference into account. She also plans to examine whether acoustic and hormonal cues, and personality traits such as shyness or boldness, can predict mate preference.