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Feature October 2013 Issue

Tufts Researchers on Ways to Help Feral Cat Population

Spay and neuter: not ideal?

As many people realize, colonies of feral cats can grow at a rapid pace, leaving them to combat miserable conditions and causing the death of millions of birds, small mammals and reptiles. In urban areas, wild-born cat colonies can also create health hazards to humans and other species, and create quality of life issues like foul odors, loud fighting and flea infestations. In the U.S., experts believe that the population of wild-born cats exceeds that of cats living with humans.

According to a new study published in the Journal of the American Veterinary Medical Association, sterilizing feral cats without removing their sexual organs would do more to control their population than spaying and neutering.

Traditional methods used to control feral cat populations involve trapping them and removing the ovaries, uterus and fallopian tubes of females, and removing the testes of the males. The method also impacts hormone production — reducing behaviors such as territorial fighting and spraying.

But veterinarians from Tufts University’s Cummings School of Veterinary Medicine propose that performing vasectomies and hysterectomies instead would preserve hormone-driven behavior that can actually help to reduce a colony’s reproduction rates.

Sex drive and social status would remain intact, allowing males to protect turf from other feral males, ward off new strays and compete for females. Females likewise continue to compete with sexually functional females. The researchers conclude that this will result in fewer successful matings.

Using data on cat populations and behavior, the Tufts researchers created a program that tracked a virtual feral cat population under different population-control regimes and with many variables that allow for such factors as age, reproductive cycle and ovulation probabilities. The academic farm game showed that the less destructive surgical technique was 10 to 90 percent more effective, depending on variables.

According to the researchers, spay-neutering methods would have to be applied to at least 57 percent of the population each year in order to have any long-term effect on feral cat colonies. For the vasectomy-hysterectomy method, however, the threshold was lower: 35 percent. And if the less destructive method had a capture rate of more than 57 percent, it would eliminate the population entirely in roughly a decade, according to the study. Neither method would work if less than 19 percent of the feral population was altered per year, however.

“The next step is to gather evidence on how it actually works in the field,” explained Tufts University veterinarian Robert J. McCarthy, DVM, MS, DACVS, lead author of the study.

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