Why do cats have bald spots in front of their ears?

Cats are known for their fastidious grooming; their soft, thick coats seem to require their constant attention. But around the ears, their fur is much sparser.

So why don't some cats have much fur there? And is it normal for cats to be a little bald around the ears?

According to experts, this isn't just normal, but possibly even essential for how cats have evolved.

Related: Is it safe for cats to drink milk?

Before investigating cats' slightly bald patches, it's important to understand that cats' fur plays a number of important roles. "It protects their skin from brush scratches," Judith Stella, an animal welfare scientist at Purdue University, told Live Science. "It's also for warmth … and social cues … and there's probably some defensive mechanism for it as well. However, it's not the same all over their body."

Most of cats' fur is formed of two layers: a finer fur undercoat, which provides warmth and thins during the summer, and a rougher covering of guard hairs, which offers the bulk of the protection. This double coat covers almost the entire body, with a few key exceptions.

"There's no hair on their paw pads — hair between their toes would gather dirt and moisture, so it wouldn't be in their best interests," Stella said. "It's a little thinner around the perianal region too, and that helps keep them cleaner."

The area around the ears is another special case. According to Stella, sparser fur on a cat's face is entirely normal. But scientists are a little less clear on why that might be. "There must be some evolutionary, adaptive reason why they are that way," Stella said. "And my theory would be that it has to do with sound."

This quirk of appearance is not limited to domestic cats (Felis catus); it's common across small cat species, such as African wildcats (Felis lybica), ocelots (Leopardus pardalis) and lynxes (genus Lynx), all of which belong to the Felinae subfamily. Big cats like tigers (Panthera tigris), lions (Panthera leo) and jaguars (Panthera onca), part of the Pantherinae subfamily, haven't evolved this same bald patch.

For Jonathan Losos, an evolutionary biologist at Washington University in Saint Louis and author of "The Cat's Meow: How Cats Evolved From The Savanna To Your Sofa" (Viking, 2023), this is a classic question in evolutionary biology. "How do we explain the distribution of traits among species? The presence of bald spots in small cats suggests that this may be the result of natural selection, that bald spots are advantageous for small cats, but not for larger ones," he told Live Science in an email. 

Stella has hypothesized that the advantage could lie in the way these different cat species hunt. "Cats can hear ultrasonic sounds, and rodents vocalize in that auditory range," she said. "Perhaps that lack of fur helps focus the sound waves into the ear or orient to where that sound is coming from."

While the small cat species are known to hunt all sorts of prey, ranging from birds to snakes, studies have shown that the majority of their diet comes from rodents, making any adaptations to detect these Animals a valuable advantage. For big cats that hunt larger Animals such as antelope or wild boar, detecting ultrasonic frequencies is less crucial for survival — which might be why they haven't evolved this same distinct fur pattern.

"The problem with studying such hypotheses of evolutionary adaptation is that it's easy to come up with a plausible explanation, but much harder to actually test this hypothesis," Losos said. "How would we test this hypothesis? Perhaps by detailed acoustic analysis of cat hearing. Or finding cats with different extents of bald patches [to] compare their ability to detect rodents or their hunting success. Or find some way to eliminate the bald patch to see if it affects hunting success. [I'm] not sure how you'd do this [and] I am not aware of anyone who has studied these bald patches."

At the moment this is just a theory, but the presence of this trait across the whole Felinae subfamily strongly suggests this fur pattern provides a specific adaptive advantage. However, Losos cautioned against jumping to conclusions without more concrete evidence.

"It's always possible that a trait will evolve for one reason and only incidentally be beneficial for another," he said. "Perhaps bald spots are favored in mate selection in small species for whatever reason, but then once they evolved by sexual selection, they turned out to be useful for hunting."