Study Suggests Coyote Control Not Enough To Improve Deer Numbers

A new study into coyote predation on whitetail fawns suggests reducing hunter harvest, rather than intensive trapping, might be the most effective way to stabilize a declining deer population.

The conclusion, based on data collected from 2010 to 2012 at the U.S. Energy Department’s Savannah River Site (SRS) in South Carolina, is outlined in a peer-reviewed article published this fall in the Journal of Wildlife Management.

U.S. Forest Service research biologist John Kilgo and four co-authors—including S.C. Department of Natural Resources deer project leader Charles Ruth—compared fawn mortality in areas where large numbers of coyotes were removed with comparable tracts where no trapping occurred.

The scientists also compared fawn survival in various types of cover.

“When the objective is to increase recruitment of white-tailed deer, we conclude that neither coyote control nor vegetation management appear effective,” they wrote. “Reduction of the antlerless harvest may be necessary to meet this objective, but this harvest strategy warrants additional research in Southeastern deer populations.”

Kilgo has been studying coyote-fawn predation at the Savannah River Site since 2006, with sobering conclusions.

Using radio collars, DNA and other modern tools, his team concluded—in studies from 2006 to 2009—that coyotes are killing at least 37 percent of newborn fawns, and most likely as many as 80 percent.

In the newest study, scientists removed 474 coyotes from three different 7,900-acre parcels and monitored 163 pregnant does over a three-year period. Those female deer produced 192 fawns, and coyotes ate most of them, despite the intensive trapping campaign.

“Among 152 mortalities, predation by coyotes was the most frequent cause of death, both before and during the coyote-removal period,” the authors found. “Coyote predation accounted for 80 percent of all mortality during the pre-removal period and 73 percent during the removal period.”

Although the new data appears to conflict with other studies that have shown trapping can reduce fawn losses to coyotes, Kilgo said most other studies involved much smaller tracts that might not yield an accurate view of the overall impact of coyotes on deer survival.

One of the biggest challenges in trapping programs is the mobility of coyotes and their ability to travel long distances and repopulate areas where trapping has occurred.

There is growing evidence that coyotes can travel long distances, which helps explain their rapid expansion across the Southeast in recent decades, Kilgo said.

“The more we learn about them, in the Southeast in particular, the more we realize they are traveling great distances,” he said.

One of the coyotes trapped at SRS, he added, was a radio-collared animal that had been tagged 237 miles away in Auburn, Ala.; and a coyote killed during a deer hunt at the site had been tagged during a study in North Carolina’s Outer Banks region.

In another documented case, several coyotes tagged at Fort Bragg, N.C., left the base, and one of them traveled to South Carolina, passing through Anderson County and eventually settling near the town of Prosperity in Newberry County, S.C.

“Effective coyote control may be even more difficult on smaller tracts than we studied, because of the more limited number of individuals that could be removed from a small area combined with the wide-ranging movements and apparently high immigration potential of coyotes,” the study said.

“Based on our findings, coyote control may not be a viable tool for most land managers in the eastern U.S. hoping to improve recruitment or increase deer population density,” the study found. “That we did not realize a consistent large increase in survival despite intensive coyote removal highlights the difficulty of achieving adequate coyote control in forested areas of the Southeast U.S. where aerial gunning is not possible.”

At this point, the authors added, “The level of coyote removal necessary to increase deer recruitment to desired levels is unknown, but appears difficult to achieve through ordinary trapping.”

Although the impacts of trapping might still need more study, the spread of coyotes has also spawned a renewed interest in trapping, according to Georgia’s Department of Natural Resources, which tracks trapping activity through trends in license sales.

The number of licenses issued peaked at nearly 3,500 in the 1970s, but declined to just 440 by 1998 because of declining interest and low fur prices.

Since then, however, the number of licenses has increased almost every year, totaling 1,129 last year, according to state officials, who believe the number will continue to increase.

In the future, Kilgo said, more research will be needed to determine whether reducing hunter harvest of antlerless deer would be the best way to preserve deer populations and manage the herd that lives alongside coyotes.

“When we first started talking about this 10 years ago, nobody considered coyotes a threat,” Kilgo said, in a telephone interview. “Today, the deer-management community is on board with the fact that coyotes can, in some situations—if not most—have an impact on deer population.”