JWM: Gene diversity high in Missouri deer

Some 1.4 million white-tailed deer (Odocoileus virginianus) roam in Missouri today, but less than a century ago, their numbers had dwindled to the verge of extirpation. It would be understandable, then, if today’s deer showed signs of inbreeding, but that’s not what researchers found when they looked at their genetics.

Instead, they found deer across the state were genetically diverse and unimpeded by barriers, allowing their genes to flow freely between populations as deer traveled across the landscape. The reintroduction of deer in the state turned out to be an ideal example of creating genetic diversity, researchers found, even if wildlife managers weren’t thinking about DNA at all more than 60 years ago.

“This is just one giant, mixed population,” said Kris Budd, a PhD candidate at the University of Missouri and lead author of the study published in the Journal of Wildlife Management.

Her study began as a bit of forensics. Budd and her team wanted to use genetics to look at deer carcasses taken by hunters and determine where in the state they had come from. But the researchers ran into a problem. Instead of finding indicators that would mark a deer as being from a specific herd, the biologists found that the deer’s genes all looked pretty similar, whether they came from the outskirts of St. Louis or the heart of the Ozarks.

“They’re flowing as one homogeneous population, as opposed to several networking subpopulations that you could potentially tell apart,” Budd said.

It was bad news for their forensics search, but good news for the health of the deer population.

“Because it’s a reintroduced population, after a population had gone through a really small bottleneck, it really was unexpected,” said co-author Lois Eggert, a University of Missouri professor and a TWS member. “But in hindsight, looking at the fact that it was reintroduced with deer from all over everywhere, it’s probably not a surprise.”

Historically, biologists believe, Missouri had about 700,000 deer —half the current population — but overexploitation reduced their numbers to just 400 by the 1920s. In 1925, the state began a reintroduction program. Wildlife managers brought in deer from other states — Michigan, Minnesota, Wisconsin — a few at a time over about three decades to occupy different parts of the state. Over time, their genetics mixed as the deer traveled between suburban gardens, farmers’ fields and forested hillsides. “They’re moving a lot,” Eggert said. “They’re even using our roads.”

Managers may not have been thinking about genetics in the first half of the 20th century, Eggert said, but they succeeded in creating the model of a genetically diverse population. “They lucked into doing this perfectly,” she said. “You have a high level of genetic diversity across the landscape that’s going to last and be able to withstand a genetic challenge in the future, say, through disease or an environmental change.”

If there’s a downside to this genetic diversity, it’s the potential that a disease could impact greater numbers of deer across the state, because they’re all likely equally susceptible. “Who knows if that would actually happen, but that’s what the theory predicts,” Eggert said.

TWS members can log in to Your Membership to read this paper in the Journal of Wildlife Management. Go to Publications and then Journal of Wildlife Management.

Header Image: One day-old fawn.