Coyotes Vs. Deer: The Predation Effect

Do coyotes eat a lot of deer? If you could remove coyotes from an area, would deer numbers go up?
Coyotes Vs. Deer: The Predation Effect

Winter is here, and in the north country that can mean deep snow, very cold temperatures for extended periods, and a time when predators can more easily take down deer. In winter, deer are eaten by mountain lions and bobcats, but in recent years the two predators we hear the most about are wolves and coyotes. Why? Because both are increasing in numbers in parts of North America, and both are expanding their range. The question is, are they impacting deer herds?

Before answering that, let me mention some interesting relationships between these two predators. One new study that utilized fur-trapping data showed that there is a “wolf effect” where the presence of wolves affects the numbers of other predators. For example, where there are high numbers of wolves, coyote numbers drop and red fox numbers increase. Supposedly, wolves won’t tolerate coyotes and kill them or drive them out, while the smaller red fox can sneak around and survive even when there are lots of wolves around.

Those researchers noted that years ago, when wolves were eliminated in the southern United States, coyotes moved in. The same happened in the North. As wolves were eliminated, coyotes moved east, reaching Maine in the early 1970s. Another interesting relationship between these two predators is the question of hybridization. DNA research shows that as those northern coyotes moved east, they hybridized with wolves. So the coyotes we now have in the Northeast, south to Virginia, have a little wolf DNA. These hybrid coyotes are not only larger than their southern relatives, but also more aggressive. The suggestion is that these two qualities make them better predators for adult deer.

This does not mean that smaller coyotes won’t take bigger game elsewhere, where the wolf DNA is not present in the coyote, but just notes that our northeastern coyotes have traits that allow them to do so more easily than coyotes from other regions. In most circumstances it is not normal for coyotes to take down adult big game, but it’s possible and it does happen. Researchers in Yellowstone National Park observed nine attempts by coyotes to take down deer and elk during one winter. The alpha male led eight of those nine attacks, and five were successful. The researchers noted that coyotes had greater success during these attempts when snow depth was significantly deeper. They also noted that two adult coyotes could successfully kill calf and adult elk when there was deep snow cover and the prey was in poor nutritional condition.

A 2013 study in Ontario looked at coyote winter predation on moose. Coyotes were captured, blood was taken for DNA analysis, and global positioning collars were placed on released animals. A clever study indeed.

They found that four coyote packs that ranged in size from two to five animals killed moose. They were able to age two of the moose, with one being very old at 20 years and another a yearling. Predation on moose occurred most often on steep slopes with deep snow with hard crust. The good news was that researchers concluded that such predation was not common and only happened during certain weather situations. However, they did state that taking one moose was beneficial to the coyotes, because in one instance the coyote pack fed for 18 days on a moose kill. One kill and food for 18 days in cold winter is a plus for the coyote.

The big question then is, do coyotes seriously impact deer? We know that they scavenge dead deer, especially in winter and spring, and we know that they kill a limited amount of adult deer in winter. But the majority of predation is on fawns in late spring and early summer, and in the South and Southeast, such predation can be significant. More on that later.

It is commonly repeated that predators only kill the old, weak or poorly nourished (hence weak) animals. Well, that’s not always true. One 12-year Maine study showed that if snows are deep enough and the weather stays cold for extended periods, coyotes will take any deer. Young, old, healthy, bucks, does; does not matter to them. But those situations are uncommon. Another Maine study added that the impact of winter coyote predation is greater when deer numbers are low, below 5 deer per square mile. And a Nova Scotia study noted that the impact of winter coyote predation on deer is lower when snowshoe hare numbers are high. Makes sense. Hares are easier for the coyotes to catch, and when their numbers are up, coyotes have an easier meal.

It seems that when coyote numbers get high in a state, legislators respond to complaints and suggest a bounty. Coyote bounties were common in the West years ago, but we now hear the call for bounties in eastern states such as West Virginia and Pennsylvania. Such requests usually die, while some are used on a county basis, then die because the county predation fund runs out of money or people realize that the bounty isn’t working. But the bounty concept won’t go away. If coyote numbers jump in your area, you’ll hear about a bounty proposal. It’s just what we do.

The question of whether coyotes killing deer affects the overall deer population isn’t as simple as it seems. There have been a number of studies done where many coyotes were removed from a large area over a long period of time. In some of those studies, the response after one year showed a jump in deer numbers, but over time, deer numbers stabilized at original levels. The majority of studies looking at adult deer predation by coyotes show that coyotes simply don’t appreciably affect deer numbers.

However, when we move to fawning season, that changes a bit. In most parts of the country, coyotes get their share of fawns, but the overall impact isn’t big. If deer numbers drop, a change in hunter harvest quotas usually brings numbers back in short order. However, there apparently is one exception, and that is the Southeast. There, studies show that coyotes are seriously impacting fawn survival to the point that deer numbers cannot remain stable, unless hunting is seriously lowered.

When coyotes are abundant, deer hunters immediately suggest trapping coyotes, as if that is the answer to the problem. But will coyote removal increase deer numbers? Since the Southeast has the worst problem with coyotes killing fawns, several studies have been done there. One Georgia study removed coyotes on two wildlife management areas. One area had 55 deer per square mile, and the second had 22 deer per square mile. Professional trappers hit the area from March to June 2011, taking 15 coyotes from the high-deer-density area and nine from the lower-deer-density area. Sure enough, fawn recruitment nearly doubled on the high-deer-density area for that year. The question then becomes, will lowering coyote numbers for one year solve the problem long-term?

A South Carolina study looked at that. They monitored fawn survival for four years, then coyotes were hammered for three years on three different 8,000-acre areas. Hundreds of coyotes were removed. Then they looked at fawn survival. This was a very time-consuming effort indeed. As you might expect, fawn survival the first year after coyote control was way up, but by the third year, the benefit was modest to say the least. The conclusion was that an intensive, and probably expensive, coyote removal program probably wasn’t worth the effort for average landowners.

Researchers have been looking at this entire situation, hoping for answers. Why doesn’t coyote control work? There are probably several reasons, but North Carolina researchers might have found the best one. It turns out that around one-third of all coyotes there are transients. These coyotes move from one area to the next, sometimes covering a 100-mile circle over several months.

Let’s say you are trapping coyotes on your hunting lease. That’s costly and time-consuming, but let’s just say that your group of hunters is adamant about removing coyotes. The North Carolina study followed collared coyotes and found that transients moved to an area, stayed there a week or so, and if a resident coyotes died, they stepped in and filled that spot. If you are trapping coyotes in an area, because of transients, you need to keep at it all the time, month after month, year after year. Even then, you might end up with the same number of predators you had when you started.

Right now, there are biologists in the Southeast who believe that the only way to maintain deer numbers is to seriously restrict hunting or eliminate it. Ouch.

Nationwide, is the coyote a major winter predator on deer? The data shows that they do eat adult deer but don’t have major impacts on population levels. But come fawning season in the Southeast, things are different. Research is proceeding and might be as important as any deer research now taking place in the country. The stakes for hunters are high, and only research can give us some definitive answers — and hopefully some solutions.

Photo: Getty Images/iStockphoto


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