Does trap-neuter-return (TNR) work?

TNR image

Does trap-neuter-return (TNR) work? This is the big question and a difficult one to respond to accurately. My understanding is that there have not been enough studies to evaluate accurately and properly whether TNR works over a large area. However, having run this website for a long time, I can confirm that I have read many news stories on the subject of TNR and there are many councils across America which have discussed TNR and the general consensus in my view is that TNR does work.

However, in my view it does depend on the extent and commitment to TNR programs and the objectives. Theoretically TNR must work in stabilising and even reducing feral cat numbers. It is the practicalities – funding and politics – which are the stumbling blocks to national success.

Note: clearly as a cat lover I am for TNR because it deals with feral cats humanely. But I accept the views of others and am willing to listen. So far I have not been convinced that any alternative is better.

Who Said That Trap-Neuter-Return Did Not Work?

Bird Lovers

From the standpoint of bird lovers and ornithologists (and those who dislike cats) TNR is a massive failure even if it works to keep down the number of feral cats. This because it places the cats back where they came from having been vaccinated and neutered. This allows continued predation on birds and native mammals. This is why many scientists involved in conservation and ornithologists detest TNR.

Barn cat wth bird in mouth
Barn cat with bird in mouth – 1916.

Ornithologists through their organisations and associations consistently seek to undermine TNR. In my opinion, they fail to realise that TNR benefits birds because as it is successful over time there are less cats and therefore less predation on birds. The trouble is people like to see instant results and ornithologists do not have the patience to wait.

Local Authorities


My reading of the situation in America is that among local authorities (at city and county level) TNR is being actively considered as the best compromised way forward to manage feral cat colonies. In truth these jurisdictions have their hands tied. There is no viable alternative because you can’t cull feral cats with poisons etc. because these methods are indescriminate and domestic cats, someone’s pet, will be caught up and killed. That would amount to state sponsored crime on a mass scale.


In Australia there is greater resistance to TNR and a leaning towards culling feral cats. This is born out of desperation and a realisation that the feral cat population in the interior of Australia is unmanageable by TNR. The problem here is about geography. The interior of the Australian continent is vast and good territory for a resourceful feral cat because of a plentiful supply of prey animals.

There are many city councils in the US which have successfully introduced TNR. Unfortunately, my understanding of the situation is that TNR is not conducted uniformly across the country and there needs to be more local government input because as I understand it many if not most TNR programs are operated by local volunteers who are dedicated to the welfare of feral cats and controlling numbers humanely.

New data proves that TNR is successful and growing in popularity and professionalism

Studies on TNR

Fortunately, there have been some studies on TNR which I will write about below. Beginning in 2002, in America, the efficacy of TNR began to be described in scientific literature.


One TNR program took place on campus in Texas. The first two years of the programme was recorded and the data presented by the scientists Hughes and Slater in 2002. During the period 158 cats were trapped, 101 were returned and 32 kittens and tame adults were adopted. The number of kittens trapped decreased significantly between the first and second year. In addition the number of complaints to the University pest control service decreased significantly.

During the following three years the number of trapped cats continued to decrease. The totals for the five years of the programme were: 226 cat trapped, 105 returned to campus. Of the cats returned 15 were eventually adopted and seven killed or died. No kittens were born on campus after the second year and fewer than 20 cats were trapped in each of the last two years of the programme, with almost half being tame cats or kittens. I have more or less quoted verbatim to ensure that the information is accurate. My reading of this study is that the TNR program was successful.


Another campus program in Florida documented the effect of TNR with an adoption program during an 11 year period. In the study a total of 155 cats were recorded over the period. After the first five years, 68 cats were present on campus and six years later 23 were present. The final disposition of all cats was: 47% were adopted (including more than 50% of cats that were initially considered feral), 50% remained on campus, 15% disappeared, 11% were euthanised, 6% died and 6% moved to nearby woods. No kittens were found after the first five years of the programme. Once again I would judge this TNR program a success.

The third study concerning 132 colonies in Florida found that the total population of cats decreased from 922 to 678 after TNR. The study was carried out by scientists Centonze and Levy in 2002. The median colony size was initially four cats and was reduced to 3 following TNR.


A fourth study which took place in 1995 in Florida concerned an animal control agency serving a large county which initiated the TNR program in collaboration with a local feral cat organisation. Six years of data before and after the implementation of TNR for feral cats showed that there was no increase in complaints or impoundments by the animal control agency notwithstanding that during the study period the human population increased by a third, which should have led to one third more cats, cat-related complaints, impounds and euthanasias. Euthanasia rates and complaints decreased during the last five years. Numbers of sterilisations increased dramatically in the six years after TNR and low cost sterilization programs were instituted for feral and owned cats. The relationship between the agency and the public improved, as did the morale of the animal control officers. In addition, TNR provided concerned citizens with the option to take action and make a difference to the numbers and the well-being of feral cats in the neighbourhoods.

Source of Study Information

I have been a bit naughty in quoting large tracts of these reported TNR programs from the book The Welfare of Cats, Section The Welfare of Feral Cats by MR Slater (an excellent and strongly recommended book). I’ve done this in order to ensure that what I’ve written is accurate.

My reading of the studies is that the TNR programs demonstrate a considerable level of success. Therefore if we are to enquire as to whether TNR works, the response is that it does work. It just needs more backing and commitment by local authorities in my view and less interference by the ornithologists!

P.S. TNR stands for trap-neuter-release (or return). Its purpose is to reduce feral cat numbers humanely.

P.P.S. Trolls, cat haters and critics can comment but please comply at all times with comment rules and make your comments concise and dispassionate.

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