University of Wisconsin-Madison researchers, working with an Illinois city and a Milwaukee County Zoo curator, hope to surgically scale down an urban deer herd that has outgrown its welcome. Sterilizing does should eventually, and non-lethally, pare deer numbers in the Highland Park herd, according to Nancy Mathews, a wildlife ecologist at the UW-Madison”s College of Agricultural and Life Sciences.

Where feasible, shooting remains the most cost-effective and reliable deer control method, Mathews says. However, many people object to firearm use in urban settings, and others frown on all lethal culling methods.

Trapping and relocation is no longer an option in most areas; nobody wants relocated deer, and many deer die soon after relocation. Concerns about chronic wasting disease will make relocation even less acceptable, Mathews says.

Contraceptive drugs have been used in the Northeast, with varying effectiveness. Every animal must be treated several times, and the treatments don”t always work.

Where rifles aren”t an option, scalpels might be the best alternative. Despite higher up-front costs, sterilization probably costs less over the long term than chemical contraception. Matthews is monitoring costs at Highland Park. She says first-year expenses will be hefty, but costs should decline over the life of the program.

The UW-Madison is the first in the nation to try surgical sterilization on a free-ranging urban deer population. Mathews has received inquiries from people across the country interested in similar programs for their communities.

“We hope to be able to show whether or not this is a viable non-lethal means of controlling deer populations in an urban environment,” she says. “I strongly believe that the strength of this project is in exploring, experimentally, one non-lethal control option so we can finally, as a profession, put some bounds on when and where non-lethal control is appropriate and practical.”

After surgery the does quickly recover and resume normal movement patterns, according to Mathews. The researchers haven”t seen any migratory movements to date, which is good because it means they”re treating resident animals and not visitors from another suburb.

Although they can”t get pregnant, the ovaries and uterus still function in sterilized does. The does will cycle several times; a breeding season that usually concludes in November after all the does are bred could extend into January. This may change typical deer behavior, as amorous bucks will pursue estrous does as long as they keep cycling.

Pregnant does that were sterilized this spring will soon give birth, so the results of this year”s work won”t show up until next year. The researchers plan to trap again in October, hoping to sterilize as many does as possible before the breeding season begins in late fall.

Whitetail does are highly philopatric – i.e., they”re homebodies. This trap-neuter-release program takes advantage of whitetail does” social behavior and homebody habits.

Mathews says a typical Highland Park doe probably spends its entire life within a home range of less than 15 acres, more or less centered around the spot it was born. Social groups of does – all related mothers, sisters, daughters and aunts – stay together throughout their lives. In agricultural country, such a group might occupy two to four square miles. “We don”t know what the collective group occupies in an urban setting, but it”s much, much smaller,” Mathews says. It”s also key to a successful sterilization program – the compact range makes it feasible to trap and sterilize nearly all the does in the group.

In 1990, Elizabeth Frank, curator of large mammals at the Milwaukee Zoo, began sterilizing whitetails that had infiltrated the zoo”s grounds. By 1993, the zoo herd dwindled from about a dozen deer to one animal, and has remained at one or two animals since then. Frank was pleased with the success of the pilot program, but wasn”t sure why it worked until she collaborated with Mathews on this project.

The two determined that the zoo population remained low because all of the does in one social group were sterilized. “Because does typically stay in their natal home range for life, no other does entered the zoo grounds,” Mathews explains. “The sterilized does eventually died and left behind no offspring to take their place at the zoo. Sterilizing most of the does in a single social group is essential for a local population to remain low. Capturing all of the females in a single social group can prove challenging, however.”

Preliminary population models say you must sterilize 80 percent of the unsterilized does every year to reduce the population. (Does are selected because a single buck can breed dozens of does in a season, and will travel miles to do it. It”s virtually impossible to trap and neuter every buck in an area, Mathews says.) Over the next three years, 60 to 80 does will be sterilized.

The team also checks treated deer for parasites and diseases, including Lyme disease, and has started collecting brain samples from road-killed deer to check for chronic wasting disease.

The Highland Park study is a joint project with the UW School of Veterinary Medicine and is co-directed with Joanne Paul-Murphy, head of the school”s Special Species Health Service. The study is funded by the city of Highland Park.

Deer in Highland Park are caught in net traps baited with apples and corn. Bucks and fawns are ear-tagged and released; does are promptly sedated and carried to the nearby operating room – a retired ambulance outfitted for field surgery, contributed by the Highland Park Police Department. There Bob MacLean, a veterinarian and post-doctoral researcher, anesthetizes the does, “ties their tubes” via tubal ligations, and takes blood and tissue samples. “In the long run, we hope to turn this project over to local veterinarians and the police department,” Mathews says.

On average the surgery takes less than an hour, with total handling time – trapping to release – of about two hours. Fast turnaround minimizes stress on the deer, Mathews notes. Every sterilized doe gets a radio tracking collar, and its movements will be monitored for the next three years. Undergraduate students from Lake Forest Community College and the UW-Madison are assisting with radio tracking.