Some cats have very dark fur due to an increased amount of melanin, a trait called melanism. Wild cats with melanism may have advantages, such as better camouflage while hunting at night, warmth in cold climates, and protection from viral infections, but they miss out on being able to communicate important visual signals to other cats, according to a study published in PLOS ONE yesterday (December 18).
What has driven the evolution of melanism is not fully understood. To look into it, researchers led by Maurício Eduardo Graipel, an ecologist at the Federal University of Santa Catalina in Brazil, examined a dataset of the appearance and behavior traits of all 40 Felidae species and combined it with a molecular phylogeny analysis.
The team found that although all cats are nocturnal to some degree, none of the feline species that show melanism are exclusively active at night. The researchers posit in the new study that this is related to white markings found on the ears of many cats, which they use to communicate. When a cat is on the lookout for a perceived threat, it raises its head high, showing off its white ears, which signals to other cats to be vigilant as well. But melanistic cats tend to have very dim ear markings, or none at all. The same dark pigmentation that makes them superior hunters at night also makes it hard for them to communicate in low light, since they can’t be seen by other cats. As a result, they can only easily communicate with other members of their species during daylight hours, when all cats, light or dark, are easier to spot. Due to this limitation, melanism appears to only have evolved in cats that aren’t completely nocturnal.
M.E. Graipel et al., “Melanism evolution in the cat family is influenced by intraspecific communication under low visibility,” PLOS ONE, doi:10.1371/journal.pone.0226136, 2019.
Emily Makowski is an intern at The Scientist. Email her at firstname.lastname@example.org.