In 2020 HSHV conducted a phone survey of past clients that were involved with our TNR program. This was done to give a sense of how well HSHV’s TNR program is doing, as well as to help benchmark the effectiveness of TNR overall.  

TNR Survey

HSHV conducted a phone survey to help determine the effectiveness of our TNR program for clients who leveraged our program between 2014 and 2017. Questions were designed to help us understand the size and condition of the colony in 2020 as compared to when TNR began at the location.

Out of the 136 individuals contacted, 24 people were available and willing to participate (just under 20% of those contacted, including one person who manages 2 colonies). Besides data, the only other criterion for being in our interview pool was having worked with HSHV to TNR a colony.

Through the 24 people contacted we were able to track 318 community cats both before and after TNR took place.  


Survey Results

Our results showed  that when a colony is able to reach 100% sterilization, we see a consistent decrease in population over time. Also, while performing TNR, we are able to further decrease populations  by adopting out unsocialized kittens before they become too old to be socialized;  this accounted for ⅓ of the total decrease in the populations, and our efforts helped many kittens find happy, safe homes to live in. 

It is difficult to put an exact number on how many unsocial cats were prevented from being born due to TNR, but reasonable estimates put the number into the hundreds, many of whom would have died as kittens.

Overall, there were initially 318 cats spread out in the 25 colonies we surveyed. A quick rundown of the numbers shows:

  • 72 kittens or friendly cats were adopted out through the TNR program in these colonies
    • This led to an immediate 22% reduction of the total population
  • Of the 318 initial cats, only 16 were never TNR’d; these 16 cats came from just 5 of the 25 colonies. 
    • For perspective, this means that means that we were able to reach 100% sterilization rates for 20 out of 25 colonies – put another way, 80% of colonies were completely sterilized
  • Before TNR, the average colony size was 12.72 cats, while 7 colonies had 5 or less cats. 
  • After TNR the average colony size was 5.24 cats. 10 colonies had 5 or less cats, and 3 had no cats left. 
  • The overall population in 2020 was at 131 cats, down 187 cats from the start population
    • This represents an overall population reduction of nearly 60%, and the colonies are expected to continue diminishing.



The findings of our survey support that TNR does work if it is done correctly. The most important things that lead to successful TNR include:

  • Sterilizing all cats in a colony, which often means setting up multiple trappings, 
  • Having the caretaker work closely with a trapper or trap themselves regularly
  • Having an attentive caretaker with the colony to help when the primary caretaker is unavailable

What we see consistently is that colonies not only stop growing when TNR’d correctly, they start shrinking. The fact that the colony doesn’t reduce too quickly has some big advantages as well, particularly when it comes to the “vacuum effect,” which you can read about in this Alley Cat Allies article.

Though the survey was not able to confirm or disprove that the average mortality rate for kittens in unsterilized colonies is 75%(Nutter2004), anecdotally we found that larger colonies had higher mortality rates, while in low density colonies it seemed that more kittens survived

Our findings are consistent with other studies on the topic, including this article published by the Humane Society of the United States: