Credit: Paul Curtis/Cornell University

The vanload of coveralled men begins cruising the suburban neighborhood around the same time the deer do.

By 9 p.m., the biologists in the van will have conceded one round in humans' bout with way too many white-tailed deer (Odocoileus virginianus) in some American communities. They also will have learned a little more about why a once-threatened species came back beyond all expectations and to the consternation of their human neighbors.

"We used to think that deer populations of 150 to 300 per square mile were impossible – or unsustainable – but that's what we're seeing in some suburban neighborhoods," says New York State Department of Environmental Conservation (DEC) wildlife biologist Dave Riehlman, crouched uncomfortably in the back of the van.

At 5:15 p.m. Cornell University graduate students Rob Pooler and Bazartseren Boldgiv leave the van, just long enough to install black-powder charges in the rocket nets they hope will temporarily trap more deer for their population-and-behavior study. The study is conducted by Cornell biologists at the request of the Village of Cayuga Heights, an off-campus community in Cornell's hometown of Ithaca, N.Y., with about 3,500 people – and probably 100-200 landscape-munching deer in the streets of the woody, 1.8-square-mile municipality.

When deer approach the net, attracted by a smorgasbord of apples, corn and apple mash from the university's cider mill, Pooler will remotely trigger the rockets to fling the 40-by-60-foot net over the surprised animals. Then the biologists will administer a tranquilizer to calm each deer while they fasten identifying tags on both ears and a collar with clearly visible numbers around the neck. The numbered collars should show up in nighttime surveillance photos and will help village residents report the animals' whereabouts to the survey team.

"We're trying to determine abundance, male-to-female sex ratios, and deer movements and habits," explains Paul Curtis, an assistant professor and coordinator of the Wildlife Damage Program in Cornell's Department of Natural Resources. "This will be one of the most intensive collaring studies attempted on deer in suburban areas of New York State, and one of the more comprehensive in the U.S."

The university biologists will not make recommendations on how the village should cope with its "deer problem." Choosing among the options – such as birth control, sharp-shooting programs to reduce populations, trapping and transporting the deer, or doing nothing at all – is up to a citizens' committee, to the elected village officials and, ultimately, to the state DEC.

Village residents failed to reach a consensus about deer-control measures, first in an opinion survey by Cornell graduate student Lisa Chase and researcher William Siemer, and later in public meetings. Most of the non-lethal methods favored by the deer-besieged residents are impractical or extremely expensive. The survey also indicated that many residents dislike deer that devour their gardens or crash into their cars on village streets. But many residents -- including some who worry about the deer problem -- simply like to see the graceful animals around town.

Back in the van that serves as a blind, the biologists see their first deer around 6:15 p.m. At other trapping sites, they erect camouflaged blinds, but tonight's trapping site (a hillside meadow of grass and cedars next to the home of a cooperative village resident) lets them observe from the vehicle. As deer approach the net, the first question is: Do they already have collars? The biologists want to save the rocket net, which will make a frightening noise, for deer that they have not yet collared.

"How many so far?" asks DEC biologist Lance Clark, anxious to help the Cornell team add more to their tally. "We've collared 35 – no, make that 37," Pooler answers, straining to see the two or three deer as they approach the bait. Bolgiv readies a night-vision scope, hoping for a better view of the animals. The winter twilight is too dim for human vision but still too bright for the electronic kind, and the deer disappear without reaching the net.

A similar opinion survey, conducted by Cornell biologists for a Colorado town where too many elk –- rather than deer – are the perceived problem, raised parallel concerns about wildlife damage and also failed to achieve a consensus about solutions. One possible solution, contraception for deer, is being tested by Pooler and other Cornell researchers at a decommissioned U.S. Army base northwest of Ithaca.

The best-available contraceptives for deer now are costly to administer and don't last more than a year or two. Pooler knows that each adult female deer usually produces two fawns a year, and without natural controls, such as coyotes or a severe winter, many of the young deer will survive and reproduce.

In suburban areas, where hunting is not permitted and tender vegetation is everywhere, the animals have no incentive to do anything but graze and make more of themselves. In the Northeast, not even disease controls over-populations of deer, according to Curtis. The only certain forms of death for suburban deer are old age and car accidents.

A cellular phone on the dashboard rings, and Pooler responds: "Cayuga Heights deer project." The caller is a village police officer. At first Pooler chuckles, but the call is not good news. "Okay, thanks. We'll be by to take a look."

By now there's plenty of darkness for Boldgiv's night-vision scope. There's just no deer. The biologists speculate on why – at a known deer-gathering area baited with tasty treats – the animals are not approaching the trap. Previous trapping at the same site had been successful, and perhaps the word is out on the deer network. Deer are quick learners, especially about threats to their well-being, and older bucks are the smartest of all, the biologists say.

Curtis is about to start a new experiment, testing a novel fertility-control method for "resident" Canada geese – such as those that fill parks, golf courses and other green places with water – that refuse to migrate. Previous anti-goose strategies – including loud noises in the air, distasteful chemicals on the grass and herding dogs – all have drawbacks. He hopes the new procedure, to be tested at two sites in upstate New York, will be environmentally sensitive, humane and cost-effective. From his years of working with human-wildlife conflicts (gulls too close to airport runways, for example, or beaver whose dam-building projects flood roadways), he knows that animals and people are part of the equation, and so is money.

Outside the van, only joggers and dog-walkers are moving. Inside, the loudest sound is growling stomachs, and someone suggests a better use for the cell phone: Order pizza. Delivered. Pooler and Curtis discuss a new site for the rocket-net trapping.

Pooler says he will check out a couple of possibilities in the morning and Boldgiv makes a final night-vision sweep of the meadow. They're giving up for the night, but not before disarming the rockets in the net. It was the warmest night after the warmest day so far in winter, and the melting snow must have uncovered natural food. Perhaps the deer are grazing elsewhere tonight. Or perhaps they're waiting, warily watching, ready to gobble up the bait as soon as the van's taillights disappear around the corner.

One grim task awaits. The phone call was notification that a deer had been killed by a car, and the animal was wearing a numbered collar. The device will have to be retrieved and reused.

"When we started tonight, we had 37 animals collared. I guess this is one step backward," Curtis says as he steers toward the scene of the accident. He drives carefully. Very carefully.