Below is the abstract to the article ‘Evaluation of the effect of a long-term trap-neuter-return and adoption program on a free-roaming cat population,’ written by Julie K. Levy, David W. Gale and Leslie A. Gale. The full article can be found here:

OBJECTIVE: To evaluate the effect of a long-term trap-neuter-return program, with adoption whenever possible, on the dynamics of a free-roaming cat population.

DESIGN: Observational epidemiologic study.

ANIMALS: 155 unowned free-roaming cats.

PROCEDURES: Free-roaming cats residing on a university campus were trapped, neutered, and returned to the environment or adopted over an 11-year period.

RESULTS: During the observation period (January 1991 to April 2002), 75% of the cats were feral, and 25% were socialized. Kittens comprised 56% of the original population. Male cats were slightly more numerous (55%) than females. At the conclusion of the observation period, 47% of the cats had been removed for adoption, 15% remained on site, 15% had disappeared, 11% were euthanatized, 6% had died, and 6% had moved to the surrounding wooded environment. Trapping began in 1991; however, a complete census of cats was not completed until 1996, at which time 68 cats resided on site. At completion of the study in 2002, the population had decreased by 66%, from 68 to 23 cats (of which 22 were feral). No kittens were observed on site after 1995, but additional stray or abandoned cats continued to become resident. New arrivals were neutered or adopted before they could reproduce.

CONCLUSIONS AND CLINICAL RELEVANCE: A comprehensive long-term program of neutering followed by adoption or return to the resident colony can result in reduction of free-roaming cat populations in urban areas.