Are Coyotes Negatively Impacting Our Deer Herds?
Let's face it, coyotes don't exactly have a great reputation amongst hunters. They've been blamed for everything from the decline of quail and rabbit populations, to lost livestock, and even the occasional missing neighborhood cat or dog. Of course, some of this reputation is deserved, and some of it is probably more lore than fact. Several recent studies, however, have shown that the boom in coyote populations over the last 30 years may be impacting more than just small game, livestock and pet numbers. More and more biologists are discovering that coyotes can have a major impact on the fawn survival of whitetail deer, as well. Just how much of an impact this is having on overall deer numbers is yet to be determined, but it is significant enough to draw the attention of many of the nation's top deer biologists.
Coyote - US Fish & Wildlife Service Photo
HISTORY OF COYOTES IN THE EAST
The coyote wasn't always a familiar face in the eastern US. In fact, in the grand scheme of things, the coyote has only recently become a permanent resident in many states east of the Mississippi River. Once a species restricted to the Great Plains region, the coyote began its expansion east with the widespread clearing of land, along with the decimation of Timber Wolf populations in the north and Red Wolf populations in the south. With the coyotes primary competition wiped out, the eastern US became a smorgasbord for the "song dogs."
It was somewhere in the late 1970s to early 1980s that the wily coyote started showing up in the western portion of my home state of Kentucky and slowly began its expansion east. To say they've done well here would be an understatement. Not only have coyotes become a common visitor to the rural areas of all the eastern states, but coyote sightings - and complaints - have expanded right into the heart of some of our largest cities.
Coyote - US Fish & Wildlife Service Photo
THE COYOTE'S DIET
As mentioned above, one of the reasons that coyotes have been able to thrive here is the abundant food supply, and the fact that they are such opportunistic feeders. In fact, it would probably be easier to list the things that coyotes DON'T eat, than it would be to list all the things that coyotes DO eat! While their primary diet consists of rodents, they are also known to eat birds, insects, fruit, livestock, as well as whitetail deer. Like many wildlife species, that diet varies seasonally, as well as from one location to another.
While coyote predation on healthy, adult deer is relatively rare, more and more studies are showing that whitetail deer fawns can make up an alarmingly high percentage of a coyote's diet during the peak fawning month. Let's take a look at a few of those studies and just what biologists are discovering about our most prolific predator.
If you were to do a Google search on coyote predation of whitetail deer, chances are you would see numerous references to Gary Lavigne - former wildlife biologist with the state of Maine, who was once in charge of the state's deer program. That's because in a 1995 report to the Maine legislature, Lavigne stated that coyote predation in Maine accounted for as much as 30 percent of the state's annual deer mortality - nearly 20,000 animals. He also reported that deer make up from 50 to 80 percent of a coyote's diet during the winter and early spring, and in some areas, that figure could be as high as 90 percent. These numbers were quite alarming to the sportsmen of Maine and eye-opening to deer managers across the country.
More recently, researchers in South Carolina conducted a three-year study on the 300-square-mile Savannah River Site of the U.S. Forest Service's Southern Research Station. What they discovered, by tracking 60 radio-collared fawns from birth, was that only 27-percent of the monitored fawns survived beyond 9 weeks, with most dying within five to six weeks of birth. Of the 44 fawns killed, coyotes were likely responsible for 38 - or nearly 85 percent. Interestingly enough, the study also concluded that ALL coyotes kill fawns, not just the dominant, experienced breeders.
A third study - this one in northeastern Alabama - convinced researchers that coyotes were a limiting factor in the number of fawns "recruited" into the herd. Their laboratory analysis of coyote scat and stomach contents showed fawns made up 27.3 percent of the coyotes' July-to-September diet, which covered that region's peak fawning months. Although small mammals (rabbits and rodents) also formed 27.3 percent of the summer diet, fawn meat was believed to be more important because of its higher nutritional value.
All of this research brings to light the fact that coyotes can and will key in on whitetail deer fawns, especially during the first month of a fawn's life. The question remains, however, if this mortality is actually detrimental to the overall health of a deer herd, and if it is, what can we do, as hunters, to help? For the answers to those questions, let's take a look at a little more research.
MANAGING COYOTE NUMBERS
In southwestern Georgia, University of Georgia researchers Brett Howze and Robert Warren chose a 29,000-acre area with a low fawn-to-doe ratio to study fawn survival in two test areas 2.5 miles apart. In the larger of the two areas (11,000-acres), the researchers removed 23 coyotes and three bobcats from January to August, but removed no predators from a second 7,000-acre block.
Shortly before hunting season, they conducted a remote camera census that estimated 0.72 fawns per doe where predators were killed and 0.07 fawns per doe where no predators were killed. In other words, there were 10 times as many fawns per doe in the area where predators were controlled than there were in the area where predators were not.
Coyote in a trap
In the northeastern Alabama study discussed earlier in the article, researchers documented a staggering jump in fawn abundance after trappers removed 22 coyotes and 10 bobcats between February and July 2007. Data from hunter observations showed a fawn/doe ratio of 0.52 before the trapping program, and 1.1 after the removals. Similarly, a remote camera census showed 0.52 fawns per doe before removal and 1.33 afterward. Combined, that's a 190 percent increase in fawn-to-doe ratios.
DOES CONTROL REALLY WORK?
The obvious conclusion from the studies outlined here is that predator control can have a significant positive impact on fawn survival in a targeted area. The problem with this, however, is that female coyotes can compensate for such losses by having larger litters and coyotes from outside the "control" area will quickly recolonize the area. This means that for a control program to be successful long-term, it will have to be maintained annually, for as long as you wish to protect the deer population in the area.
Having said all this, the question still remains whether or not coyotes are a threat to our deer herd. Based on the research and the growth of the eastern US deer herd over the last 30 years, I would say the answer is "no." Coyote populations seem to be somewhat self-regulating, and our thriving deer population seems to handle the loss to predation well. Research shows that adult mortality in coyotes runs between 30 and 40 percent for adults and as high as 70 percent for juveniles, but can vary greatly from year to year. Coyotes are susceptible to a multitude of canine diseases, including distemper, parvo, mange, hepatitis and rabies, and outbreaks of disease can severely impact local populations. Just as with losses from human control, though, coyotes can usually rebound quickly from disease outbreaks by breeding younger and having larger litters.
Just because coyote numbers are self regulating, however, doesn't mean that coyotes can't have a negative impact in areas where deer densities are already low due to other factors - such as EHD outbreaks, illegal harvest, etc. It is in areas like these, that we must closely monitor coyote populations and their impacts on deer herds, and - when necessary - increase hunting and trapping pressure in order to protect the young fawns beyond that critical first month of life. Because if one thing is certain in all of these discussions on coyotes and deer, it is this: a hungry coyote will never pass on the opportunity to make a nice, warm meal out of a young whitetail deer.
Brian Grossman is a wildlife biologist, freelance writer and avid outdoorsman from Mt. Washington, Kentucky. You can visit his web site at www.PoorBoysOutdoors.com.