URI researchers hope to reveal why rare cottontails don’t breed like rabbits

A team of URI students have been studying the behaviors of rabbit pairs for signs that may indicate why the breeding rate is so low.

KINGSTON, R.I. – February 9, 2021 – While viewing hundreds of hours of infrared video footage of captive New England cottontails at Roger Williams Park Zoo, University of Rhode Island senior Hannah Petit watched for signs of breeding behavior.

The rare rabbits, which are being bred in captivity so their offspring can be released into the wild, are not nearly as prolific as their reputation would suggest. After dozens of pairings between male cottontails and the zoo’s 15 females during one round of breeding attempts in 2019, just three became pregnant.

“We’re trying to see if we can find out why not all pairs are breeding,” said Petit, an animal science major from Pawtucket. “They spend a lot of time in close proximity to each other, but we’re not seeing many mating attempts. The low pregnancy rate doesn’t seem to be due to an issue with fertility or maintaining their pregnancy; it seems like they’re not even trying to mate.”

Petit and a team of seven other URI students have spent the last year reviewing more than 300 hours of video and coding the behaviors the rabbit pairs exhibit for any signs that may indicate why the breeding rate is so low.

“You would expect them to breed like rabbits, but they don’t,” said Justin Richard, URI assistant professor of animal science and the leader of the project. “Are there behavioral influences that might impact whether pairings are successful, and can we understand what that behavior is to predict the best pairings? We don’t really know about the breeding behavior of this species because they’re so difficult to observe in the wild.”

The New England cottontail is the only native rabbit in southern New England, but its populations are low due to competition with the non-native eastern cottontail and other factors. URI, Roger Williams Park Zoo, Rhode Island Department of Environmental Management, U.S. Fish and Wildlife Service and other partners are undertaking a comprehensive conservation initiative to rebuild the populations and better understand their biology and ecology.

According to Richard, the two cottontail species are very difficult to distinguish in the wild and are most active at night, so the New England cottontail is problematic to study except in captivity.

While analyzing video of the cottontails, the URI students make note of every social interaction that occurs between the rabbit pairs, from how often they run by each other to the frequency of close approaches and the number of mounting attempts.

“Our sample size is very small so this is just preliminary so far, but we’ve seen pairs that ended up breeding that approached each other more often,” said Petit. “The biggest thing we noticed is that the more attempted mounts, the more often it resulted in pregnancy.”

“Some are receptive to being in close proximity to other individuals, and others aren’t,” added Richard, a former beluga whale trainer at Mystic Aquarium who studies the reproductive biology of animals that are difficult to study in the wild. “We hope to add in physiological measures as we advance this research to try to understand if there is a reproductive cycle involved or if it’s just behavioral compatibility. In a lot of breeding programs, they’re finding that when females are offered a choice of mates, they’re more productive. We’re trying to apply that to this critter.”

Lou Perrotti, the director of conservation at Roger Williams Park Zoo and leader of the cottontail breeding program, said that research partnerships like this provide significant benefits.

“The work Justin and his class have been doing can help answer some of the questions we have with reproductive issues, mate choice, and kit rearing that we have seen with this species,” he said. “The findings of this study could potentially help bolster kit productivity for the program in the upcoming years. This is also a great opportunity for students to get conservation experience. There’s no better way to inspire the next generation of conservationists.”

The project has certainly been inspiring to Petit, who plans to enroll at URI as a graduate student next fall to continue her research with Richard and the cottontails. After completing the analysis of the videos, their next step will be to set up experiments to see whether the females will become pregnant at a higher rate if they have a choice of males with which to mate.

“I really enjoyed learning so much about this one species that really needs our help,” Petit said. “They’re vulnerable now, so I’m happy that I’m able to contribute something meaningful to this important work.”