27/10/2015 8:49 AM AEDT | Updated 27/10/2015 8:57 AM AEDT

Some Cat Colors Linked To Aggression, But Don't Base Your Pet Choice On It

The individual cat is what matters.

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Researchers thought calico cats would be more likely to display aggression.

A new study suggests a possible link between feline aggression and certain coat colors and patterns, but the lead researcher warns that people looking to adopt a cat shouldn't be basing their decision on how the animal looks.

"It's not that your average white cat is an angel and your average calico is a devil," Dr. Liz Stelow of the University of California-Davis told The Huffington Post. "We're looking at a continuum here."

Stelow and her team looked at data from 1,274 anonymous cat caretakers who answered an online survey about their pets’ behavior for a study published on Oct. 14 in the Journal of Applied Animal Welfare Science. The survey included questions about how often the cats engaged in various aggressive behaviors -- like hissing, biting or scratching -- as well as questions about the likelihood that the cats would display aggression while being handled or at the vet.

Owners of female cats with "sex-linked" color patterns -- meaning tortoiseshell, “torbie” and calico cats -- reported a higher frequency of aggression than owners of female cats of other colors.

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A tortoiseshell cat. Researchers found cats with this type of coloring were reported as being more aggressive, but the survey participants may have been influenced by the cats' reputation.

"Sex-linked" means that these specific color patterns are linked to genes on the X chromosome. Only male cats with an extra X chromosome can exhibit such patterns, making them extremely rare.

The survey's findings seem to back up these cats' reputation for being more difficult than other felines. Some people even refer to the alleged feistiness of tortoiseshells as “tortitude.”

The data also suggested that cats with gray and white coats, as well as cats with black and white coats, may have increased aggression -- a result Stelow said the researchers did not expect to find.

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A cat with gray and white coloring. Researchers were surprised to find that survey participants reported these cats as having higher aggression levels as well.

But a caveat to the study is that it's based on aggression as reported by the cats' caretakers -- researchers did not independently observe any cats themselves.

While the results may indicate that stereotypes about tortoiseshell behavior are based in reality, the opposite also could be true, said Mikel Delgado, a certified cat behavior consultant and Ph.D. candidate in psychology at the University of California-Berkeley.

If people have the preconception that cats of certain colors possess certain traits, they may be more likely to notice and report those traits in their own cats.

“There could be biases if people hear words like ‘tortitude’ -- or if they show me a photo [of their tortoiseshell cat] and I say, ‘Oh, she must be feisty,” then you might think, ‘Oh, she is feisty!’” explained Delgado, who led a 2012 study exploring how cats' coloring influences how people see their behavior.

And while at least one headline has dramatically proclaimed that the study says cats with certain coat colors “make better pets,” Stelow said she absolutely does not think anyone should be using the study as a guide to pet adoption. 

"Many factors need to go into what pet is right for you," she said. "I wouldn’t want anyone to rely on this information exclusively."

Stelow noted that even though some groups of cats had higher aggression scores, the reported aggression for all groups was relatively low. 

A cat's overall score for aggression towards humans was based on caretakers answering four questions about how often their pet exhibited particular aggressive behaviors, like hissing or biting. Each of the four questions asked about a different behavior, researcher Philip H. Kass explained in an email. 

Caretakers used a 0-5 point scale to express how often their cat engaged in each aggressive behavior. A score of  "0" meant  “never”; 1 meant “less than once every 6 months”; 2 meant "more than once every 6 months”; 3 meant “more than once per month”; 4 meant “more than once per week”; and 5 meant “more than once per day.”

Since there were four sub-categories, each cat could end up with a maximum score of 20.

But the median score for the majority of color categories was 0 -- meaning the cat owner rated his or her pet as never expressing aggression at all. Even the tortoiseshell/calico/torbie group only had a median score of 1 (out of 20 possible points for aggression).

“[The statistically significant differences] may also be due to the relatively low levels of aggression in cats overall, as evidenced by the low median scores, so that any difference, however small, comes out as significant,” the researchers wrote. They also noted the differences are small enough that they could have been due to variations in how different cat owners interpreted the questions.

Stelow said the main purpose of the study was to serve as a preliminary measure to determine whether more research in the area is a good idea. 

"We’d like to have some of the geneticists take over and take a closer look at ...  inheritance of coat colors," she said. 

Both Delgado and Stelow said they hope that sensationalistic news stories about the study don't cause potential cat adopters to make the wrong decisions. Anyone seeking a pet should pay attention to the behavior of each individual cat they meet, rather than making broad judgements based solely on coat colors.

After all, Stelow has a beloved calico cat herself.

"She’s not the least bit aggressive, but she is a nut," she said.

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