Surviving a Coyote-Eat-Fawn World
by Mary Thill
In football, to flood the zone is to overwhelm defenders with more receivers than they can possibly cover. Sometimes nature runs this play, but on defense. Mayfly nymphs, for example, sprint for the surface of a lake in such huge numbers that trout simply can’t eat them all. This is known as predator swamping.
Right now, hidden in the ferns, white-tailed deer are running a swamp defense. Fawns, born in tight synchrony in late May and early June, are Bambi wobbly at birth. For their first 20 days they make easy prey for coyotes. But by overmatching the predators with more fawns than they can eat, enough deer survive to keep the population healthy.
Robin Holevinski is a PhD student interested in coyote predation on deer in New York State. Fawn kills decline steeply through mid-June, she found. By July coyotes have largely moved on to other prey, according to a series of recent studies by Holevinski and other researchers with Roosevelt Wild Life Station at the SUNY College of Environmental Science and Forestry, in Syracuse. “In summer, 55% of carcasses killed by coyotes were fawns, 24% were woodchuck, 18% were turkey, and 4% were goose and cottontail,” Holevinski emailed.
Scientists and grad students used GPS collars to track coyotes to kill sites and examine what they had eaten in Otsego and Steuben counties, in New York State’s southern tier. In winter, 42% of the carcasses researchers found were scavenged deer (killed by vehicle collision or injuries sustained during hunting season), 28% were scavenged livestock (none killed by coyotes), 27% were too decomposed to know what killed them, and only 3% were animals clearly killed by coyotes.
In the Adirondacks, coyotes gradually filled the top predator niche after the wolf and cougar were hunted to local extinction in the 1890s. Unlike most western coyotes, the ones that migrated east will prey on deer, but new evidence finds it’s not their primary source of protein in the Adirondacks.
Coyotes here now appear to favor beaver over deer. The percentage of coyote scat containing deer in SUNY ESF’s Huntington Wildlife Forest, in Newcomb, has declined from a historic peak of around 90 percent from 1975 to 1980 to less than 50 percent today, even though deer are more plentiful today, according to research by Scott Warsen, who looked at long-term trends in coyote diets from the 1920s to present. Warsen is a 2012 graduate of ESF with a Master of Science degree in Wildlife Biology and Management now working in Deer River, Minnesota, for the U.S. Forest Service.
Roosevelt Wild Life Station also estimates that there are 2.5 pairs of coyotes per 10 square miles in the Adirondacks. They arrived at this figure by analyzing DNA in scat, and by playing recorded coyote calls and listening for responses. Three-person teams fanned out across rural areas in New York State in the summer of 2010 to listen for howls on windless nights.
If you are interested in trying to count coyotes near your home, here’s a pro tip from the study: an individual coyote can be detected only as it joins the group howl, within the very first few seconds.
For more information on Roosevelt Wild Life Station research in the Adirondacks and around the world click here.