The Vacuum Effect

vacuum effect in cats

image from AlleyCat Allies

Catching and killing feral cats is animal control’s traditional approach for feral cats.

Catch and kill attempts may temporarily reduce the number of feral cats in a given area, but two things then happen:

  1. intact survivors continue to breed
  2. other cats move in to the now-available territory

This phenomenon is known as the vacuum effect, and it is documented worldwide.

With TNR there are no more kittens and the population stabilizes. The returned neutered cats’ lives are improved.

Plus with TNR, behaviors and stresses associated with pregnancy and mating, such as yowling or fighting come to a stop.