Do Moon Phases Affect Cats?

Many people have made an anecdotal connection between chaotic human behavior and the full moon. According to this Washington Post article, it just isn't true, but what about animals? Are they more affected by the phases of the moon than humans are? Barbara B. writes:

My cat Benjamin is the most wonderful animal in the world approximately 20 out of 30 days a month. I truly believe he is a “lunatic” since I have noticed that his personality changes occur around the time of the full moon, when he becomes moody and aggressive. Do you believe my observation and if so what do you suggest?

Thank you for your question! While much of what we typically think of as "full moon behavior" in humans has little basis in fact, there has been a study that seems to confirm that cats may be affected by the phases of the moon. In it, veterinarians and their assistants noted a 23% increase in cat visits to emergency rooms on nights when the moon was more full. There are several ways to look at this study, including the possibility that outdoor cats could become more active due to the increase of nighttime light from the moon. Whatever the reason, some cats certainly can vary their behavior in a cyclical way. 

For some cats, these aggressive spells are indicative of the fact that they aren't getting enough of a daily play workout. Over time, this lack of "hunting" activity can manifest as nervous energy and frustration that builds and builds until it just has to come out. Scheduling playtime at least twice a day will certainly help to get some of that energy out before it becomes a problem.

A cat can also become agitated because of smells. Laundering bedding that Benjamin has his scent on could even be enough to set him off. Also, if an interloper cat outside is spraying, you might not notice the scent but Benjamin certainly would. We have a good post on removing this annoyance here:

One other thing that could be creating problems for Benjamin is pain. If you trim his nails every few weeks, one could be pressing into his toe pad and causing some pain until you trim them the next time. This sort of thing takes some detective work to sort out, but it's worth considering. Handle him (gently) all over and see if he shows a reaction. You didn't mention his age, but he could have arthritis. That can tend to become more or less painful depending on the barometric pressure and temperature.

Pay close attention to his litter box habits and the food and treats he consumes as well. Is there something you feed him from the table every now and then? If there's a recurring physical malady, it may take a little time to be noticed. Yes, it's a long shot, but the more attention you pay the Benjamin's habits, the easier the cause of his crazy spells will be to discern.

We wish you and Benjamin the were-cat all the best!