Cats are divisive pets: the feline companions are loyal companions to some, and mischievous murderers to others. There’s evidence suggesting that cats in general see us more as a mix between landlords who let them stay in a human hotel, servants that feed them, and odd-looking kittens who can’t hunt properly. More specifically, certain cats seem more chilled out in their day-to-day lives, whereas others seem to be fairly tetchy and aggressive, and some new evidence may be able to shed some light on this. A statistical survey, published in the Journal of Applied Animal Welfare Science, has appeared to make a connection between a cat’s fur color and its inherent aggressiveness towards humans.
For the study, the team of veterinary experts from the University of California Davis collected survey answers from an online questionnaire. From 1,274 cat owners, a range of data was requested, including fur color, their opinion on their cat's aggressiveness towards humans and other domestic cats, how they displayed any combative features when dealing with humans and cats, and how their cats behaved at the veterinary clinic. The aggressiveness was ranked on a numerical scale.
As the survey reveals, female “orange” cats (tortoiseshells, calicos, and torbies), female black-and-white cats, and female gray-and-white cats all tend to be more aggressive towards humans during everyday interactions, handling, and veterinary visits. The calmest cats were those with gray, black, white or tabby fur.
As the adage goes: correlation does not imply causation, and just because there is a correlation between fur color and aggressiveness in cats, it does not necessarily mean that innate aggressiveness causes that particular skin color to emerge, or vice versa. However, perhaps there is a link here: this could be a phenomenon known as a “spandrel.”
In evolutionary biology, a spandrel is a physical feature that appears as a byproduct of the evolution of another characteristic. So it is perhaps possible that the fur color changes are a spandrel: an evolutionary byproduct, an indirect effect of any inherent genetic disposition towards being more aggressive.
The silver fox breeding experiment that took place in the Soviet Union from 1959 bred specific foxes with each other in an ultimately successful attempt to make them tamer and calmer around humans. Surprisingly, this increased tameness was accompanied by physical alterations, with their coat color, tail and ear shapes all changing to appear somewhat more appeasing to the human eye: essentially, they looked cuter. This was perhaps due to a reduction in their adrenaline production as they were artificially selected and bred to produce tamer offspring.
Spandrels are the result of an effect known as pleiotropy, and it is likely that the seemingly disparate link between fur color and aggressiveness in cats is an example of this in action, with certain colors being produced as a byproduct of their genetically-controlled innate hostile behavior.