Deer Watch

With white-tailed deer populations still growing and invading settled areas, all sorts of people are learning firsthand about the big mammals' behavior

10-01-1994 // Peter Nelson

At about 10:00 P.M. on an autumn night not long ago, a white-tailed deer wandered into Northampton, a city of 30,000 in western Massachusetts. The seven-point buck ambled down State Street, took a left on Gothic, sauntered between the courthouse and the bank and found himself on Main Street. Then maybe a car honked, or the gestalt of neon and street lamps frightened the animal-and he leapt through the window of an art supply store, possibly believing the reflected image to be an opening through which he could escape.

Once inside, true panic took over. For 10 awful minutes, the terrified animal charged forward, leaping into the walls, over shelves, up onto display tables, bouncing back, slipping, falling, spilling paints and pigments and leaving blood everywhere from the cuts he sustained breaking through the glass.

Passersby heard the clamor and called the police. Finally, by sheer trial and error, the deer found the way out, leaving behind a rainbow-hued mess and $10,000 worth of damage. He was last seen running into the woods at the edge of town.

According to recent estimates, there are perhaps 25 million white-tailed deer in the lower 48 states-nearly two times more than some estimates only a decade ago. Stories of modern deer encounters range from the garden variety (as in the chomping of prized plants) to a deer's mad dash one morning last fall through a crowded passenger terminal at Dulles Airport near Washington, D.C. Northampton alone has had deer in the art store, a college dining hall and a supermarket.

Along with the anecdotes has come curiosity: from researchers, motorists, gardeners, hikers. "Since we've started dealing with the deer population explosion, there's been a new focus of interest," says wildlife biologist Paul Lyons at central Massachusetts' huge Quabbin Reservoir, which is surrounded by deer-filled forest. "It's not surprising to see a rash of human-deer related problems," he adds. "Remember, our own population is growing and spreading too."

As humans have spread, they have actually created habitat for deer. "Urbanization provides a deer with everything it could ever want," points out Jay Kirkpatrick, director of science and conservation biology at Zoo Montana in Billings: "Nice ornamental shrubs, gardens and lawns to eat, half acres of woods here and there to bed down in-and nobody can shoot it. The only predators are cars." Whitetails survive in deserts, swamps and farmland as well as forests and are found from southern Canada to Panama. In some areas, hundreds may be found in a square mile, and their chomping can reduce understory vegetation to such an extent that bird populations and other species relying on brush and low branches are affected. Deer numbers altogether may be up as much as 5,000 percent since the turn of the century; meanwhile, natural predator populations have declined.

Part of the whitetail's success is due to its prodigious fecundity. Does breed as early as 6 months in some areas, and at 18 months in others, then bear young every year and frequently give birth to twins and triplets. Over the course of an average 10-year lifespan, a single doe and her offspring might produce 100 fawns.

Yet for all their ubiquity, the big mammals still intrigue scientists. "When I first started studying deer, I thought they were already pretty well understood," says John Ozoga, retired wildlife research biologist at Cusino Wildlife Research Station in Michigan's Upper Peninsula, who has observed deer social organization for the last 30 years. "The journals were full of articles. Since then I've learned how little we really know--about communication, stress, segregation of the sexes, dominance hierarchies."

One of his questions, for example, concerned how deer divvy up territory in summer or home ranges in northern climes. Ozoga found that the female offspring of dominant does usually claim birthing areas near their mothers, which in turn tend to claim the same birthing areas they claimed the year before. The mother and female-offspring territories overlap slightly; third-generation andother related females move farther out.

Scientists have long known that after fawns arrive in May and June (usually weighing around 5 pounds and able to walk soon after birth), the mothers become extremely territorial. But in 1986, Ozoga reported new discoveries about the mothers' vigilance. He found that does separate newborn twins (and the occasional triplets), making sure their bedding sites are at least 200 feet apart until the young are about 25 days old. "The separation," Ozoga explains, "is a predator-defense strategy. The fawns lie hidden, alone. The mother stays in the vicinity, vigilant, several hundred feet away." And if a predator takes one fawn, the other is still safe.

The doe also drives away her yearling offspring during her new fawns' first month. As the summer progresses, she becomes more sociable with her yearlings. Around this time of regrouping, male yearlings strike out on their own to find a place in groups of unrelated males. Why? Ozoga's work revealed the source of the yearlings' motivation to depart: Related females gang up, convincing a yearling male to leave, he says, by "beating the daylights out of him."

The young males develop their first antlers between April and September. The antlers are at first covered by a thin velvet, which brings blood and nutrients to the growing tissue until the velvet shrinks and sheds in September. The antlers drop off during the winter.

Antlers are essential to the social organization of the fraternal groups, and some biologists contend that determining social order is the main function of the antlers, not actual combat. Wherever the truth lies, deer seldom kill each other, though in rare instances, sparring bucks with similarly sized antlers can fatally lock their racks together.

"The yearlings seem driven to spar with other males," says Ozoga. "I've watched very large, impressive males lower their massive racks and allow younger bucks to stick their antlers in and rattle them around, even though a big one could annihilate a little one if he wanted to. They seem to do it simply to bond with one another."

During warm months, when white tails are not reproducing, sparring or socializing, they are busy eating, favoring broadleaf plants, new spring buds-and often garden plants. Some gardeners claim a mixture of raw eggs and water, painted on plants, can deter deer. Others say scents from predator scats, particularly bobcat feces (not exactly common at your local nursery), do the trick. But biologists agree on only one tried-and-true method: a good, high fence.

The deer become more active in the fall, as the season of their rut approaches and both sexes respond to waning daylight with hormonal changes. Females come into estrus, and males mark their territories by leaving scent on trees and on the ground. Dominant bucks rub more often against tree trunks, leaving behind a substance secreted by a gland in the forehead to express their high social rank and mark their breeding range. Males often also scrape clear patches on the ground in which they both urinate and leave another secretion produced in glands located between their toes.

Laurie Allman, a naturalist at the Carpenter St. Croix Valley Nature Center in Minnesota, northeast of the Twin Cities, was giving a lecture one summer day in the early 1980s to a group of Girl Scouts during a hike along the St. Croix River. "We had a young male deer which someone had brought in as a fawn," Allman says. "They found it all alone and assumed it was an orphan, since there was no adult around. It's unfortunately quite common for people to do this, even though the deer are seldom actual orphans. We were working on ways of feeding the fawns without imprinting them on humans, hut this time it didn't work."

The young male started following her group, Girl Scouts giggling, though Allman instructed them to ignore the animal. Her efforts to scare it off failed. "It began cutting around the edges and circling the girls, as if it were trying to group them. Then it went up on its hind legs, almost as if it were attempting to mount one of them. When I stepped in, it reared up again, lashing out with his front hooves at me until I had to grab him by the shins to hold him off. We ended up standing there on the trail, doing a little waltz. The Girl Scouts screamed with laughter; they thought I dance with deer every day."

Girl Scouts aside, the deer's behavior was what a biologist might expect from a whitetail, especially from a maturing male. Kicking, an activity sometimes mistaken for play, is an aggressive act common among deer. "You don't want to get inside a pen with an antlered buck during the fall," says Mike Nelson, research biologist at the National Biological Survey's Kawishiwi Research Lab in Ely, Minnesota.

But most people injured because of deer encounter the animals on roadways. Dan Harman, a biologist at the University of Maryland Center for Environmental and Estuarian Studies, and George Waring, a zoologist at Southern Illinois University in Carbondale, both have studied how deer behave around highways. They've also looked at the effectiveness of reflectors and bumper-mounted deer whistles; neither gadget has proved to be effective. Says Harman about the whistles, "No scientific results prove they work, though they haven't been fully tested under all circumstances."

Deer are attracted to highways partly because of the salt used in winter, which leaches into the surrounding soil, and partly because of the forage planted on the sides and in the center strip. "Usually when deer cross freeways, they're moving from an open feeding area to a protected bedding area," says Waring. "They'll do it in regular cycles, sometimes a couple of times a day."

The frustration for motorists is that deer react to cars in seemingly illogical ways, especially at night, often waiting until a car is quite close and then running out in front of the vehicle just in time to get hit. Explains Harman, deer freeze under bright lights as a standard response to an approaching threat. "They have extremely effective night vision," he says. "And they don't appreciate bright lights. They may not know it's a car coming, or they may think they're hidden and we can't see them." So they wait, probably until they feel they must make a move. "Then," Harman adds, "when it's time to escape, their biological reaction is to try to get out in front of whatever is pursuing them, get ahead of it-which, of course, they can't."

The worst time may be dusk, in autumn, just before a storm, when the barometric pressure is dropping. "They seem to try to feed before the weather turns bad, so they can get to shelter when it does," he says. The most dangerous situation is a doe trying to lead her fawns across the road. The fawns may hesitate, then panic and run to catch up.

Deer are less mobile in the North's winter, their most trying season. With thick insulating coats (deer don't even melt the snow they sleep on), they are rarely bothered by cold. But once snow reaches a foot or more, deer can't move around easily, and scarce food sources may be out of reach. Decreased mobility also makes deer more vulnerable to predators, so they collect in deer yards. So-called "yarding," or concentrating in areas where snow is shallower, in some regions is "in large part an anti-predator strategy," says the National Biological Survey's Nelson, who has been following deer dispersal patterns in Minnesota, working with data collected during the past 20 years.

Yards range in size from less than a square mile to 30 square miles. "The deer trample down the snow and leave escape trails," explains Nelson. "And there are more of them to warn each other, plusthe sheer number decreases the mathematical probability that any one individual will be selected by a predator. Where you don't have snow, you don't see yarding behavior."

In Nelson's Minnesota study region, predator avoidance is particularly relevant; this habitat is one of few remaining in the United States with a significant population of wolves, perhaps numbering as many as 1,800.

"I once watched a deer trying to swim across a lake," Nelson says. "A pack of wolves saw it and waited on shore. The wolves would move to where the deer was about to emerge, and it would turn around. Normally if deer flee to water, the wolves are reluctant to follow. But after about four or five hours of this, one wolf jumped into the water, swam out, strangled the deer by the throat and dragged it back to shore.

"I've also seen a case of three wolves circling a deer standing absolutely still. All three wolves approached, one at a time, within 5 meters, for 5 minutes, then simply walked away. My speculation is that the deer had been aggressive when first approached earlier by the wolves, which had then stepped back after perceiving that deer as a threat. A hoof kick can be serious; it was a large deer."

Few readers of this magazine are likely to see a wolf kill a deer. But you'll almost certainly encounter whitetails somewhere, soon-or read about them elsewhere. As the animals' numbers continue to multiply, so do the number of scientific studies conducted about them and their behavior. One massive study on the biology and management of white-tailed deer lists some 10,000 research projects in its bibliography. That's not counting the informal research conducted every day between deer and humans learning to live together in the nation's backyards, gardens, roadways and forest trails."

Northampton, Massachusetts, writer Peter Nelson last wrote about bat-eating boa constrictors for National Wildlife.

Join today and get a 1 year subscription to National Wildlife magazine
     Flickr Icon           Find NWF on Facebook.           Follow NWF on Twitter.           YouTube Icon    
Connecting...
Certify your yard today!