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Females who were familiar with their mates had healthier babies. "But of the kits born to neighbors, 20 survived. "Only two kits born to non-neighbor pairs survived their first year," Martin said. Another measure of success would be discovered a year later. 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.īut 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. Less than a month later, the researchers trained their eyes on the rabbit burrows, waiting to see which ones produced kits. "The female rabbits always chose one male over the other, and in most cases, one male was extremely preferred."Įach 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.įemales were then paired with males from one of four categories: neighbor, non-neighbor, preferred and non-preferred. "Females are the limiting factor in many breeding programs for mammals, because they tend to be the choosiest," Martin said. Rabbits were housed in rows of neighboring open-air pens, alternating between male and female, thus giving each female a choice between two males. David Shepherdson, the zoo's deputy director of conservation, organized a rabbit "speed-dating" program. So in the spring of 2010, with a grant from the Oregon Zoo's Future for Wildlife program, Martin and Dr. 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.

Animals are typically paired based on estimates of genetic relatedness.

But like many endangered species breeding programs, the miniscule bunnies were plagued with low birth rates and incompatibility among mates. In 2001, the Oregon Zoo had become the first in the world to breed the highly endangered Columbia Basin pygmy rabbits.