A study on the effectiveness of street cat population control has just confirmed what we’ve known all along – cats really do have nine lives. Or rather, it’s awfully hard to reduce their numbers.

Stray cats can pose health risks for humans and suffer from poor health themselves, leading to efforts to curb their increasing numbers.

The most popular cat population-control method is called TNR (trap-neuter-release), and returnd stray cats to their original location. But a 12-year-long study by researchers from the Hebrew University of Jerusalem recently published in the PNAS journal showed that it is only partially successful, and that ultimate results are achieved when 70 percent of cats are neutered.

The study focused on the central Israeli city of Rishon LeZion. In the first four-year period of the study, there was no population intervention; in the second period, researchers organized an intensive neutering program in half of the city; and in the third four-year period TNR was applied, as much as possible, to the entire cat population.

A stray cat in Jaffa. Photo by Anna Wachspress

Neutering in only half of the city’s zones did not reduce the cat population, which researchers attribute to the immigration of unneutered cats into the area. Trying to neuter the entire cat population led to a 7 percent reduction of the population, but a rebound increase in the number of kittens was noticed – probably due to an increase in their survival due to lack of competition with the neutered, less aggressive cats.

The ideal solution, researchers note, would be to ensure that 70% of the street cat population is continuously neutered. To negate the rebound effect, they suggest controlling food resources during the TNR campaigns, for example by establishing feeding stations and prohibiting feeding in other public areas. This way, the cats would be properly fed, and it would be easier to catch them for neutering.