TNR and the Vacuum Effect

cat 03Removing cats from an area by killing or relocating them is cruel and pointless. Scientific evidence indicates that removing a feral cat population just opens up the area to an influx of new cats. Each time cats are removed, the population will rebound through a phenomenon called the “Vacuum Effect”, which just creates an endless cycle of trapping and killing.

The Vacuum Effect is what happens when an animal population is removed from its home range. The empty habitat attracts other members of the same species from surrounding areas, who move in to take advantage of the same resources that attracted the original group (food, shelter). Killing or removing the original population does not eliminate the resources. It only creates a “vacuum” that inevitably draws in other animals living nearby.

A habitat will support a population of a certain size. If resources remain, the population eventually recovers. Any remaining cats will produce more kittens and at a higher survival rate, filling the habitat to capacity.


  • Stabilizes feral cat colonies
  • Improves cats’ lives
  • Answers the needs of the community
  • Protects cats’ lives
  • TNR works-other methods don’t

Who Does TNR?

TNR is successfully practiced in hundreds of communities around the country by various organizations. Some of the top locations and organization that practice TNR are listed below.

  • Baltimore, MD
  • Washington, DC
  • Austin, TX
  • Jacksonville, FL
  • Topeka, KS
  • San Francisco, CA
  • Los Angeles, CA
  • Cook County, IL
  • Humane Society of the United States (HSUS)
  • American Society for the Prevention of Cruelty to Animals (ASPCA)
  • American Animal Hospital Association (AAHA)
  • Stanford University
  • Texas A & M
  • NC State University
  • University of FL
  • Disneyland
  • 260+ nonprofit organizations throughout the US