Black cats may be traditionally considered an unlucky sign, but the very genes that produce their colour could help researchers fight disease.
Black cats: Lucky for some?
In theory, animals with unusual colourings would be more likely to go extinct over time, unless the genes which gave them those colourings also conferred some sort of survival advantage.
In the case of black cats, or more particularly jaguars, researchers at the National Cancer Institute and University of Maryland in the US believe that a gene that makes their fur turn black may also give them the edge against infections.
They believe that, as humans have a similar gene, it might be possible to boost human resistance to disease.
Researcher Dr Stephen O'Brien said: "In understanding how wild species like cats evolve genetic resistance to disease, we might discover new natural genetic resistance that might help in human disease."
The black fur gene in jaguars is called MC1R. If the human version of the gene is mutated, it gives some people red hair.
The primary function of the gene, part of a family called 7-transmembrane receptors, is to regulate what is allowed through the cell membrane.
So a mutated transmembrane receptor might in theory be better able to prevent certain viruses or bacteria from getting in.
No black lions
Dr O'Brien said: "HIV enters cells through a 7-transmembrane receptor called CCR5.
"So perhaps the selective pressure that allowed these mutations to survive in cats may not be to camouflage.
"Perhaps the mutations cause resistance of the cats to bugs."
A domestic cat appears to have approximately 10 genes which influence coat colour and appearance, producing 40 or so distinct breeds.
However, not all wild species of cat - for example lions and tigers - have a black mutation.
The research is published in the journal Current Biology.