August 2, 2016
Categories: Research, Animal Behavior, Adoption

Does your shelter or rescue group counsel adopters on how to carefully and gradually introduce a new cat into the family? If so, many of your adopters may well be ignoring your advice — and things work out anyway.

A couple of weeks ago, Million Cat Challenge co-founder Dr. Kate Hurley of the UC Davis Koret Shelter Medicine Program opened a study, forwarded to her by Maddie’s Fund® Director of Research Dr. Sheila D’Arpino, on aggression that might arise between cats in a family when a new cat is adopted. Dr. Hurley reached out to the Million Cat discussion group with her thoughts on the findings, and agreed to share them with us here as well.

First, some background. The study was based on a 62-question survey sent to 375 people who had adopted a cat from an animal shelter in New York State. A total of 252 households responded, of which only 128 had multiple cats. Around half of those households reported fighting between the cats when the new cat was introduced, and half also reported they had simply put the cats together without any introduction period.

Here are Dr. Hurley’s comments:

Perhaps surprisingly, the method of introduction (gradual versus waiting a few days versus immediate introduction) did not correlate with the likelihood that the cats would fight. The author is skeptical about this finding, suggesting that the “gradual” introductions reported may not have been sufficiently gradual or performed correctly. However, the fact remains that there was no effect reported from this sampling, which may well reflect what adopters are capable of/likely to do in real life, despite our best counseling efforts.

Another key finding was that half the adopters introduced the cats to one another immediately, suggesting this practice is common even in those cases where the adopter may have been advised otherwise. To be totally honest, I’ve been guilty of this myself, feeling sorry for my latest foster cat hanging out alone in my guest room and letting him out to join the family the very same evening I brought him home.

Another notable finding is that fighting between cats was common, occurring about half the time. The good news was that over half the cats had accepted one another within a month, and over 90 percent had accepted each other within a year.

Although not mentioned, perhaps a hopeful finding is that all these cats were still in their adoptive homes, even though conflict with the resident cat(s) was so common.

Dr. Hurley’s “takeaways” included:

  • Setting realistic expectations may be the most important component of a successful adoption of an adult cat into a multi-cat home – letting people know that cats that don’t get along initially are still very likely to accept each other reasonably well over time.
  • Maintaining open lines of communication with adopters so that if fighting occurs they will reach out for help is likely to be more helpful than hanging our hopes on preventing intercat conflict through sufficiently gradual introductions.
  • Recognizing that in a few cases, cats simply won’t get along with another cat at least under circumstances that can be realistically provided by an average adopter. In those cases, a return can be seen not as a failure, but simply as a lesson learned about two cats and what they prefer.

The study abstract can be read, and the complete study purchased, at the link below.

Levine, E. et al., Intercat aggression in households following the introduction of a new cat. Applied Animal Behaviour Science, March 2005, Volume 90, Issue 3, 325 – 336. DOI: