March 19, 2003

Surgical sterilization snips away at deer overpopulation

ITHACA, N.Y. -- If deer have fetal memories from the womb, the fawn born to Doe 106 later this spring will have quite a story to tell about events the morning of March 8, 2003.

The unborn fawn's mother was the subject of "TNR," in the jargon of biologists who deal with animal overpopulation issues: She was trapped (unharmed, in a suburban neighborhood with too many white-tailed deer to suit some people), neutered (by tubal ligation in a procedure that spared the developing fetus) and returned (wearing numbered I.D. tags, radio collar and a slightly dazed expression).

The other 220 deer in Cayuga Heights, N.Y., a 1.8-square-mile village near the Cornell University campus, are too busy -- digesting landscape greenery, dodging automobiles and procreating -- to care about the fawn's story. But inquiring scientists, as well as 3,300 residents of the village and federal and state regulators, want to know: Will this experiment to reduce deer populations have a long-term effect, and should the Cayuga Heights model be copied nationwide?

The Doe 106 story actually began in 2000, before she was born, when a team of wildlife biologists led by Paul Curtis, an associate professor of natural resources at Cornell and an expert in what some call "problem animals," began a wildlife field study in suburbia. Using humane traps, surveillance cameras, radio collars and numbered I.D. tags, the team produced estimates of deer demographics by age, sex and movement patterns. Next, the biologists helped a citizens' committee analyze options for deer-population control: special-permit hunts by sharpshooters or archers (which met with widespread opposition), relocation (illegal and also unworkable because other deer would take their place), contraceptive birth control by dart guns (costly because "booster" shots are required annually and also illegal because of firearms laws) or TNR surgical sterilization.

Although costly, surgical sterilization became a more feasible option -- at least for a one-time experiment --- when a property owner stepped forward with a grant, and the New York state Department of Environmental Conservation offered in-kind and graduate-student support. A cold, snowy winter delayed the experiment. But the weather forecast for a relatively warm Saturday, March 8, encouraged the biologists to set their traps the night before. The first two traps, installed on private property with owners' permission and baited with corn, were empty. The third had a young, pregnant female deer with no I.D. tags, meaning she had not previously been trapped and was a likely candidate for sterilization.

Still pregnant but for the last time, Doe 106 is attended by, from left, anesthesiologist Lysa Posner,with an 'Ambu' bag to help its breathing; veterinary technician Samantha Koba; veterinary student Joe Churce; and natural resources technician Peter Mattison. Cornell News Service photoCopyright © Cornell University Click on the image for a high-resolution version (1132 x 912 pixels, 1024K)
At 7:50 a.m. Curtis and his assistant, technician Peter Mattison, collapsed the cage-like trap, which is made of flexible netting and folding braces, and subdued the struggling animal with an injection of muscle-relaxing sedative. They tied her feet and rolled her onto a stretcher. Mattison called ahead to alert the Cornell College of Veterinary Medicine's large-animal hospital where a team of six awaited -- a veterinary surgeon, a theriogenologist (reproduction specialist), an anesthesiologist, two veterinary technicians and a veterinary student. (The operation can be performed safely by only three people.)

Inside the clinic, where the more conventional patients are horses and cattle, the 120-pound deer was placed on her back on a tilting operating table so that gravity could move internal organs, including the uterus with its fetus, out of the way. Large-animal surgeon Brett Woodie shaved the deer's abdomen in order to make three, half-inch incisions for the laparoscopic procedure.

Because the yearling was pregnant, the veterinarians decided on a tubal ligation. An alternative procedure, an ovariectomy to remove the ovaries, would have reduced production of hormones needed to carry the fetus to term. The tubal ligation, cutting and searing closed the fallopian tubes with electrosurgical instruments, would prevent any more fertilized eggs from reaching the deer's uterus. The 20-month-old animal's first successful pregnancy would be her last.

It was all over in 25 minutes, and the biologists clipped I.D. tags numbered "106" to the animal's ears, fastened a leather radio collar around her neck and checked it with the antenna and receiver they would later use to track her movements. Back at the original trapping site, another injection reversed the effects of the tranquilizer. By 10:50 a.m. the doe was on her feet, running off to join the rest of the herd.

Curtis and his colleagues don't put much stock in the notion of fetal memory. They expect, however, that the fawn of Doe 106 will have plenty to tell them, just by being born, probably being trapped and tagged, and becoming another data point in the experiment. Meanwhile, a more theoretical study at Cornell is trying to predict whether such tactics have any long-term effect.

An unrelated TNR study, of feral cats roaming a Florida university campus, recently showed that systematic neutering can greatly reduce a "problem" population -- but only if many of the animals are adopted as pets.

"Yes, these deer are tame, and yes, some people think they're cute and set out food for them," says Curtis. "But they're still wild animals, and by law you'd can't adopt them." Then again, by providing deer with a more comfortable home than they ever had in the wild, "I guess we have adopted them."