Eastern Coyotes: How Predators Affect Deer Herds
June 06, 2013
Are predators such as coyotes negatively affecting our deer herds? In an article in the February 1999 issue of a well-known hunting magazine, a wildlife biologist wrote, "The answer is generally no, but it all depends. The positive and negative impacts of coyotes on our deer herds in the East are poorly understood. More research is needed. The origin of the coyote's establishment in the East is still a matter of speculation."
Does this quote tell us anything? I don't think so. This guy should have been a politician. Why would I say that about someone? Because that quote was from me!
Deer in the West learned to live with coyotes for eons. Granted, there are always peaks and valleys in predator-prey relationships, but deer that possessed the instincts to avoid predators passed their survival traits onto their young. This is important because it increased fawn survival when populations were at a low point. In other words, the does that are better "hiders" of their fawns are the key to re-establishing a population.
But, what happens to the deer in the East that have never lived with coyotes? Dr. Michael Chamberlain, a wildlife professor at the University of Georgia, says, "It's important to understand that deer in most areas east of the Mississippi River have had to deal with coyotes only recently. Their expansion has been extremely rapid relative to range expansion in other mammals, particularly larger mammals.
As gray and red wolves disappeared from the Northeast and Southeast, coyotes began their eastward expansion, which drastically accelerated during the 1970s and 1980s. By the 1990s, coyotes had reached the East Coast and now are ubiquitous throughout the Eastern U.S."
Theories suggest that the present-day Eastern coyote is most likely a cross with gray wolves that dispersed across Canada into the Eastern U.S. and/or the red wolf that was found in the Southeast.
Hybridization between coyotes and wolves may also explain why coyotes are in every state east of the Mississippi River. This makes sense when you consider the extensive predator removal that occurred during the previous two centuries. With declining predator populations, breeding with each other may have been the only option. Nowadays, many of these hybrids have backcrossed with coyotes.
Recent genetic studies lean toward crossbreeding with wolves as the most likely reason coyotes are larger in the East than in the West. We also know coyotes in the East are completely different than their Western cousins. We also know coyotes will breed with dogs. Interestingly, research has proven that crosses between coyotes and dogs, or "coydogs," only survive a generation or two. Whatever the current day makeup of coyotes in the East, one thing is certain: Almost nothing we thought we knew about coyotes in the West pertains to those in the East.
By definition, recruitment rate is the number of fawns per adult doe. This important index can help you predict future declines or increases to your deer herd.
All hunters know most does will drop twin fawns. But the real question is how many of these fawns will survive to six months of age? This figure is what biologists call the herd's recruitment rate. Depending on where you live, a recruitment rate of 1.0 fawn per adult doe is a good average. When the recruitment rate drops significantly, this index is the key in deciding whether or not to reduce your antlerless harvest.
How do you measure recruitment rates? Hunters can estimate fawn-to-adult-doe ratios with simple observation data. This is when you record the number of bucks, adult does, and fawns you observe while hunting. Many state wildlife departments use butcher shops or check stations, but most use harvest data to determine recruitment rates.
For years, the recruitment rates within many deer herds had no significant change. Sure there were dips, but they would always balance out. Recruitment rate data was one of those indexes biologists collected but little attention was given to it because it was almost always consistent.
In 2008, Kip Adams, a certified wildlife biologist and director of education and outreach for the Quality Deer Management Association (QDMA), collected recruitment rate data from around the country. Within the QDMA's "Whitetail Report," Adams determined that many states, specifically those east of the Mississippi River, were almost all reporting significantly reduced recruitment rates. Why?
Are predators having a significant role in reducing recruitment rates? In some areas of the country with too many deer you can make the argument predators are actually helping the deer herd. But, Adams reports on recent research in Alabama, Georgia, and South Carolina that confirms bobcats and coyotes have significantly reduced fawn recruitment rates. Additional data from Pennsylvania showed black bears were just as efficient as coyotes when it came to fawn predation.
It wasn't too long ago when I (and other biologists) routinely said, "Once you think you've shot enough does that you have scared yourself to death, shoot some more!" Although this management goal worked in many parts of the country for years, it no longer applies to these areas with reduced recruitment rates.
Many times hunters question whether it's a good idea to harvest an adult doe versus a fawn? From a management point of view, if I have a very low recruitment rate, I'd recommend taking the fawn. The reason is because older adult does are generally better mothers and have a higher chance of dropping multiple fawns.
Bounties for coyotes in West Virginia and Utah are being considered. Other states are lengthening their coyote season to year-round. South Dakota just added $1 on certain licenses for predator control. No matter what we do, one thing is sure: We're not going to get rid of them!
Without a doubt, people in the East will see increased predation to farm animals, domestic dogs and cats, and deer because of coyotes. Urban deer problems will lead to urban coyote problems, and once a pet or child gets mauled or killed by a coyote, maybe the antis will wake up to the concept of predator control? Like them or not, coyotes are now a permanent fixture in the East.
In the East there's a new sheriff in town, and his name is Mr. Coyote. This critter's impact on our deer herds will have to be measured very closely on a yearly basis. When it comes to coyote control methods, we do know that very little works on a long-term basis.
Increasing recruitment rate data indicates improving herd health, and this translates to an increased harvest of bucks and does. Declining recruitment rates within proper habitat conditions indicates something is wrong. Whether increasing or declining, the recruitment parameter is something every biologist (and hunter) should be watching very closely.