URI researchers hope to reveal why rare cottontails don’t breed like rabbits
New England cottontails are seen in this image taken from a video used in URI research investigating the breeding behaviors of the captive animals. (Photo courtesy of Justin Richard)
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.”