Trap-Neuter-Release Isn’t The Most Effective For Controlling Feral Cats

By Debra Kelly on Friday, September 25, 2015
White Cat in Urban Setting
“The Naming of cats is a difficult matter; / It isn’t just one of your holiday games. / You may think at first, I’m as mad as a hatter / When I tell you a cat must have three different names.” —T.S. Eliot, “Old Possum’s Book of Practical Cats”

In A Nutshell

According to Tufts University, the popular trap-neuter-release program for controlling feral cats isn’t the most efficient. Replacing neuter surgeries with vasectomies and hysterectomies will keep established colonies more stable, and with a male cat still producing hormones but unable to make kittens, he’ll be more capable of protecting his female cats from unaltered males. The cats won’t have the extended lifespan that neutered cats do, and simulations show that a policy of TVHR has the potential to humanely eliminate entire colonies of feral cats over a handful of years.

The Whole Bushel

Feral cats are a huge issue all over the world. A 2013 study by the US Fish and Wildlife Service took a look at how much of an impact the millions of feral cats in America have had on the environment, and the results were pretty staggering. They estimated that ferals were responsible for killing as many as 3.7 billion birds and 20.7 billion small mammals like mice, rats, squirrels, and rabbits every year.

Those are huge numbers, and the numbers of feral cats living in the US alone are just as surprising. The population fluctuates a lot and is impossible to count, but in 2004 experts were tossing around numbers like 70 million when it came to estimating the feral cat population of the US alone. That’s more cats than the environment can realistically support, and animal rights advocates have been struggling against the seemingly insurmountable wave of feral cats all over the world.

For many groups, the humane solution is a trap-neuter-release program. Cats are caught, surgeries performed, vaccines given, and they’re returned to their colony. In most cases, their ears are tipped so people can tell at a glance they’ve been sterilized. The idea is that over time, the colonies will die out and the population will be reduced humanely, but a study by Tufts University suggests that this movement—which is gaining worldwide popularity—isn’t the best idea.

Researchers took a look at the dynamics of feral cat colonies. When a male cat is neutered, it changes his behavior. That’s why most people who keep male cats in the house have the surgery performed. An intact male cat is more likely to fight and to defend his turf, and in a feral cat colony, that usually means there’s one man who’s the boss and who’s protecting his territory. Neuter the cat and his behavior becomes much less focused on being at the top of the colony’s hierarchy. While he won’t be fighting or breeding afterward, he’ll simply be replaced by the next most dominant male.

Tufts is suggesting that rather than neutering male and female cats (or spaying the females, if you’re using the American terms), a more efficient solution is to perform vasectomies and hysterectomies on the feral cats. By leaving most of their reproductive system intact, there are a couple of benefits. The cats are still producing hormones, which means males will still retain their desire to fight and keep other males off their territory and away from their ladies. He won’t be producing any kittens, but he’ll be fighting off others that are trying to.

Female cats who mate with a male who’s had a vasectomy rather than been neutered often show signs of a pseudo-pregnancy, meaning that even if they haven’t been trapped yet, their reproductive cycle changes without producing more kittens.

Neutering also extends a cat’s natural life span, meaning it takes longer and longer for a colony to age and die. A vasectomy and hysterectomy doesn’t change that part of a cat’s life, either, and there’s a huge difference in the numbers Tufts sees in their simulations.

How successful a TNR program is, no one seems to know for sure. Even when an entire colony is removed, there are still more and more cats that come in to take their place. Many feral colonies are descended from discarded housecats and former pets that are no longer wanted, meaning human behavior is responsible for a large part of the problem. There haven’t been any concrete, satisfactory studies that look at just what the impact of TNR is on a colony, but simulations suggests TVHR could be more successful.

By keeping the dynamic of a colony stable while it ages, the entire colony could go entirely extinct within 11 years by altering only 35 percent of the cats in the colony each year. That’s compared to TNR, where 82 percent of the cats would need to be caught and altered every year.

Certainly, there’s no easy answer when it comes to humanely controlling a feral cat problem that we largely help create in the first place, but Tufts’ solution is certainly an intriguing one.

Show Me The Proof

Tufts Now: Study shows feral cat control could benefit from different approach
National Geographic: U.S. Faces Growing Feral Cat Problem
Smithsonian: Feral Cats Kill Billions of Small Critters Each Year