October 20, 2014

Cornell Faces Setbacks in Efforts to Sterilize Local Deer Population

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The University’s efforts to control the local deer population since 2009 have brought about unintended and unforeseen consequences, garnering some national news coverage over the past few weeks.

The white-tailed deer population present in the community had left fields excessively grazed and the wild habitat of certain songbird species altered prior to intervention by the University, The Washington Post reported on Sept. 29.

Collisions with cars and the destruction of agricultural plots used for research were also consequences of the skyrocketing deer population at the time, according to an August 2009 University press release.

By 2009, Cornell “needed to find a solution” to control the deer population that would satisfy everyone, The Post said.

That summer, a group of Cornell researchers began a five-year pilot program that aimed to reduce “deer abundance and associated impacts” by 75 percent on central campus and by half in less-developed areas outside campus, according to the University. The program, which combined doe sterilization with controlled hunting, used different methods to control deer populations in a range of environments.

The researchers chose to surgically sterilize dozens of does on the University’s central campus, where hunting is “not feasible or legal,” according to the release. Additionally, a majority of these does were equipped with radio collars that would monitor factors such as movement patterns and fawning rates.

In addition, controlled hunting was allowed in peripheral areas of campus as a means of preventing outside deer from entering the main campus.

However, the sterilization method employed by the University — tubal ligation, “in which a doe’s fallopian tubes are either blocked or severed” — would lead to an unexpected result, according to The Post. Though the birth rate decreased, the overall number of deer remained steady over five years.

Prof. Paul Curtis, natural resources, attributed this unusual observation to an increasing number of bucks, despite a reduction in fawn and doe numbers.

“There were about 100 deer on campus when we started, and there were still about 100 deer [five years later],” Curtis, who is also an extension wildlife specialist in the department of natural resources, told the The Post.

It turned out the does were in heat more often. Since the ligated deer were unable to become pregnant, they “continued to produce chemical signals of readiness to reproduce,” which attracted the bucks, according to The Post.

The lack of success the University faced in controlling the deer population led administrators to reevaluate its approach, turning to a nuisance deer removal program which used a combination of volunteer bowhunters and a “trap and bolt” method to kill deer, according to an August article by The Syracuse Post-Standard. These herd culling efforts began the previous year in the summer.

These methods elicited criticism from members in the local organization Cayuga Deer, who have called the practices “inhumane,” The Sun previously reported. According to Curtis, this particular method has been effective in reducing the deer population on campus.

“In winter 2013, our camera survey indicated there were 100 to 105 deer on campus. After the nuisance deer removal in 2014, the camera estimate was about 58 deer remaining on campus,” Curtis told The Washington Post.

Though Curtis and his team have begun new experiments involving ovary removal to control the deer population, they are still facing issues sterilizing deer: out of three deer that were given ovariectomies, one became pregnant again.