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Effects of coyotes on deer getting new look

Posted on August 8, 2013

Springfield — Can coyotes and deer co-habitate in Illinois? That’s a question that cannot be answered by a single research study or survey.

But what biologists at the University of Georgia are doing should be of interest to Illinois hunters, landowners and wildlife watchers. Researchers  there are taking a close look at the effects of coyotes have on whitetail populations.

Although coyotes rarely take adult deer in Illinois, they are primary predators of deer fawns, according to an Illinois Natural History Survey fawn survival study conducted in different locations within the Chicago area. That INHS study found that coyotes killed 20 percent to 80 percent of the fawns in different populations.

“Coyotes cannot reduce deer populations because they do not often take adult deer (in the Midwest), but they may slow population growth in high-density areas through their predation on fawns,” the INHS study concluded.

In the UGA study, biologists aren’t specifically studying fawn predation, but rather how coyote pressure impacts overall deer behavior.  They’ll be studying whitetails in two controlled environments – one with coyotes and one without coyotes.

Results of both settings will then be compared.

Questions the researchers hope to answer include, “Do predator-stressed deer eat as much and as well as non-stressed deer?” and “Does the presence of high concentrations of coyotes affect rut behavior among bucks?”

Other things the study will address is coyote’s affect of a deer’s weight, birth rates, sex ratios of fawns and what happens when deer are driven from their preferred ranges and forced to live on marginal habitat?

For Illinois deer, a point of study that has interest is whether pressured deer more or less susceptible to disease.

Past INHS research here at home have found that high concentrations of coyotes does indeed have some effect on whitetail behavior. Deer living in areas of Illinois with a large number of coyotes act differently than deer living in aras of the state that are mostly free of coyotes.

The UGA study on coyotes’ effect on deer behavior got underway earlier this summer. It follows a 4-year study the UGA Deer Lab began in 2010 on the predator’s effect on fawns.

For Illinois deer hunters and deer watchers, the connection to the UGA study is interesting, because Georgia, like Illinois, is in the middle of a coyote population explosion.

“Since the 1960s, Georgia’s deer population has risen from scarcity to areas of local overabundance through restocking efforts and science-based management,” Charlie Killmaster, Georgia’s State Deer Project Coordinator, said. “The population has since declined to a healthy level; however, a better understanding of the role of coyotes in deer management is needed.”

As with the deer behavior study, the fawn study is attempting to determine the balance of negative and positive effects of coyotes.

“It is well understood and accepted that coyotes do eat deer,” John W. Bowers, Assistant Chief of Game Management for the Georgia DNR, said in a news release explaining the fawn study. “However, whether coyote predation is a benefit or an obstacle to deer management strategies is not black and white. We are hopeful this cooperative research effort will provide additional information for use by deer managers and hunters in making responsible management decisions.”

Graduate students began the research work three years ago by conducting trail-camera surveys. The camera surveys were done repeatedly to assess fawn-to-doe ratios before and after the coyote removal.

They later began monitoring coyote abundance.

Researchers in the fawn study are using what is called a “capture-mark-recapture” technique in which DNA found in deposited scats are being used to identify individual coyotes in the wild. Researchers will also evaluate the seasonal diet of coyotes and assess the extent to which they impact fawn recruitment by conducting an intensive coyote removal across two large study sites.

“Our hope is that this model can be used by deer managers to make informed management decisions,” Will Gulsby, a PhD student in Wildlife Ecology and Management at UGA, explained.

Here in Illinois, DNR has estimated there are in excess of 30,000 coyotes in the state, an estimate that is likely conservative. Their diets here vary, according to research.

In fact, a study last decade led by the Max McGraw Wildlife Foundation looked at coyotes in northern Illinois and analyzed scat contents to determine what coyotes were eating.

Diet items varied across space and time, which reflects the flexible food habits of coyotes. The most common food items were small rodents (42 percent), fruit (23 percent), deer (22 percent), and rabbit (18 percent). Domestic cats were found in only 1.3 percent of scats, and human-related food (garbage, pet food) was found in only 1.9 percent of scats. 

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