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Doing the Math

May 29, 2014

An undergraduate investigates a solution to growing feral cat populations. Photo by Ken Clare

By Angie Vicars

Cats, cats, and more cats! But we’re not talking about the fluffy darlings of the Internet. We are referring to feral cats like the ones you might find eating from a dumpster behind a local restaurant.

Feral cats are descendants of domestic cats, but they’re wild and not used to human contact. They live in colonies and tend to roam freely. Some consider the presence of feral cats a nuisance, claiming they can lead to declines in wildlife populations and spread infectious diseases to people and other animals. Others devote significant time and resources to the welfare of these untamed felines.

Many communities, including Knox County, Tennessee, are struggling to find better ways to control growing populations of feral cats. One controversial program being implemented by some municipalities is known as Trap-Neuter-Return (TNR). Sometimes described as humane care, TNR is an alternative to cats being trapped, taken to animal shelters, and euthanized. Instead, the cats are neutered and returned to their colony.

There are still many questions surrounding the effectiveness of TNR programs, but a recent collaborative UT research project may help provide some answers. The study represents the combined efforts of the National Institute for Mathematical and Biological Synthesis (NIMBioS), the College of Veterinary Medicine, and Young-Williams Animal Center, the public animal shelter for Knox County.

Lindsay Lee

Lindsay Lee

In the summer of 2011, NIMBioS assigned an interdisciplinary team of undergraduate and graduate students to investigate. One of those undergraduates was Haslam Scholar Lindsay Lee, who was named a Rhodes Scholar in 2013 thanks in part to the mathematical modeling research she conducted during the project.

Lee and her fellow team members developed a method to predict the results of using a TNR model to stabilize or reduce selected feral cat populations in Knox County. The five-year study focuses on colonies with a human overseer who makes sure the cats are fed and neutered.

“I remember when we got our first results being so surprised that they were congruent with results in the [comparable research] literature,” Lee says. “The papers we found said a 60 to 70 percent spay rate would be needed to create a population decrease, which is around what we got from our model.”

The team’s research indicated that neutering cats seasonally would help reduce the total number of operations needed and stabilize population growth. The findings also suggested that using TNR for adult female cats in December and January—the time before mating season—might further decrease the feral cat population in highly populated colony areas.

Knowledge gained from this ongoing study could impact the efforts of Young-Williams, which currently performs spaying and neutering operations on site and with a mobile shuttle.

The researchers will continue data collection on Knox County’s feral cat populations and are working on a paper to submit for publication. Whether the findings will compel Knox County to sanction a TNR program remains to be seen.