Deer as prey
As the deer gun season approaches, there's a tendency to ignore predators as a factor that limits deer populations. And after reviewing deer harvest numbers released by several state wildlife agencies, it's no wonder.
Last year, for example, Pennsylvania hunters killed an estimated 343,110 white-tailed deer. The harvest included 133,860 antlered deer and 209,250 antlerless deer. Ohio hunters killed 218,910 deer during the 2012-13 seasons.
In West Virginia the total harvest of 131,444 white-tailed deer included 56,658 bucks, 45,169 antlerless season deer, 24,571 bow-killed deer, and 5,046 deer killed during the muzzleloader season.
Michigan sold 700,101 deer-hunting licenses last year, and those hunters killed an estimated 418,000 deer. Male hunters purchased 90 percent of those licenses.
In addition to the toll taken by hunters, white-tailed deer must also deal with a variety of natural predators.
Predation is the most interesting mortality factor because it involves large familiar animals. Though rarely observed and difficult to quantify, predation helps keep deer populations under control.
Where deer and wolves and/or mountain lions coexist, deer are big predators' most important prey. Mountain lions are solitary animals, and they kill a deer every four or five days. Wolves live in social packs and require more food to feed the entire pack on a regular basis. A pack of 10 wolves kills far more deer than a pack of four.
In the northern Rocky Mountains, lynx and wolverines can be added to a list of deer predators. Elsewhere, however, others fill the vacant niche once occupied by cougars and wolves.
Coyotes are the top deer predator in the East. Some studies have shown that coyotes are responsible for up to 80 percent of fawn mortality, and small packs of coyotes chase and kill adult deer. About twice a month I hear coyotes chasing deer at night right here on the ridge.
Black bears (and grizzly bears out West) rarely fail to take fawns whenever they encounter them. It's not worth hunting fawns because they're small, so most bear-fawn encounters are a matter of chance. Fortunately the window of fawn vulnerability is brief, so bear predation is not significant.
In fact, most deer killed by predators are fawns, sickly or aged adults, or deer exhausted from slogging through deep snow. Only mountain lions and wolves routinely take healthy adult deer, and even they prefer the young, sick, or weak. A healthy adult deer may be no match for a cougar or pack of wolves, but they don't go down without a fight. The risk of injury, even to a big predator, is real, so predators almost always choose prey that is in some way disadvantaged.
The list of other predators that can take deer in the East is short. Domestic dogs sometimes chase deer to the point of exhaustion; one study from the 1970s estimated that dogs killed 500 to 1,000 deer annually in Pennsylvania. An exhausted deer is relatively easy for a group of dogs to kill.
Bobcats can take deer in deep snow, and they sometimes attack deer on beds at night, but their total impact is minor. Fishers probably take a few fawns, but as a recently reintroduced species in some states, fishers are too few to be an important factor. And foxes are too small to be a serious predator of anything except newborn fawns. I've also read accounts of great horned owls, eagles, and ravens taking fawns and small deer, but I suspect many of these reports are scavengers eating road-killed deer.
The white-tailed deer's reproductive potential is its saving grace. A polygamous species where a few males can service many females and females typically have multiple twin-bearing years, deer can sustain heavy losses from predators and hunters and still maintain a stable or even growing population.
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On a lighter note: If you enjoy watching birds at feeders, but don't have access to a feeding station, check out this live feeder cam in Manitouwadge, Ontario: http://www.livestream.com/feederwatchcam. You'll probably see some northern birds you won't recognize, so keep a field guide handy. Watch for evening grosbeaks, redpolls, siskins, and gray jays. And if you're lucky, you might see the suet-eating ruffed grouse on a platform feeder.Contact Dr. Shalaway via his web site (www.drshalaway.com), via e-mail at firstname.lastname@example.org or at 2222 Fish Ridge Road, Cameron, WV 26033.