In an attempt to reduce its on-campus deer population by sterilizing does, Cornell University scientists inadvertently created “buck magnets” that regularly drew in new male deer from miles away. Not only did messing with the reproductive cycle of the does backfire in a big way, but it was also far more costly than allowing hunters to cull the herd.

In 2009, the Ithaca, N.Y., campus held a population of about 100 deer, which were destroying habitat, eating gardens, and causing collisions with vehicles, The Washington Post reports. Recognizing the need to reduce the population, but also bowing to pressure from those opposed to lethal control measures, a team of biologists captured 77 does and gave them tubal ligations—the doe’s fallopian tubes were blocked to permanently sterilize them. The operations cost $1200 per deer, a figure that doesn’t include the value of help donated by Cornell’s College of Veterinary Medicine.

In the five years since, fawn numbers have declined, although three sterilized does were somehow still able to give birth. The doe population also declined slightly, yet the overall deer population remained the same. “There were about 100 deer on campus when we started, and there were still about 100 deer [five years later],” said Paul Curtis, an extension wildlife specialist at Cornell.

Curtis and his team of biologists realized that the sterilized does kept coming into estrous, attracting bucks from long distances and offsetting the declining birthrate. The Cornell administration ended the expensive program and instead hired trappers and allowed volunteers to bowhunt where it was feasible. From 2013 to 2014 shooting and hunting reduced the deer population from 105 to 58 animals.

“Because the bow hunters are volunteers, this program is essentially cost-neutral,” said Bernd Blossey, chair of the Cornell Deer Research and Management Committee, who added that he’d been skeptical that the tubal ligations would be successful. “Maybe it was worth doing it in a sophisticated way to say we tried in the best possible way and it didn’t make a difference.”

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