When you think of panthers, those black, mysterious—not to mention dangerous—leopards of the wild, your imagination may wander to obscure jungles in India or Africa, where few humans set foot. And your imagination would not be far off, for such animals are among the rarest large cats in the world.
“Black panthers are uncommon,” Nicholas Pilfold, biologist with the San Diego Institute, wrote on Instagram after a 2019 sighting of black leopards in Kenya. “Only about 11 percent of leopards globally are black. But black panthers in Africa are extremely rare.”
The sighting he referenced was reportedly the first panther sighting in Africa in 100 years.
The black leopard, or Panthera pardus, is often referred to as a “panther.” Native mainly to the tropics of southeast Asia, and preferring to stick to the shadows of the jungle while avoiding areas of large human settlements, these wild cats are sighted occasionally, but infrequently.
Their dark coats are caused by a condition known as “melanism,” increased levels of pigment in the skin or fur.
Though panthers are widely believed to be stark black, they often have coats in varying shades of dark brown.
Melanism is believed to be the result of a recessive gene, though a variation of this trait known as “pseudomelanism” is actually what causes a regular leopard to have spots.
“Melanism is hypothesized to be an adaptation to environments in which a dark coloration provides camouflage from predators or prey,” Dr. Pilfold wrote in a paper published in African Journal of Ecology.
In the case of panthers, the quantity of the pigment melanin is simply much greater than that of a regular leopard.
If you look closely, you can often see the faint outline of spots on a panther’s dark coat.
Scientists do not know the exact evolutionary reason for a panther’s dark coat, nor what causes it to be so rare.
Some hypothesize that its rarity may have to do with the inability of a spotted leopard to communicate with a panther.
In a 2019 study, zoologist Maurício Graipel and his colleagues with the Federal University of Santa Catarina in Brazil hypothesized that a leopard’s spots are critical to communication. However, the dark coat of a panther obscures its spots, rendering communication ineffective between the two types of felines.
“The black coat color acts as camouflage at almost any time, but therein lies the problem,” Graipel explained. “When a black cat runs into a spotted cat, it may not be easy for them to understand each other.”
Most notably, panthers lack the white markings on the tips of their ears and tail, which scientists say are vital to feline communication.
“Since white is the most light-reflecting color, we considered that these white marks might play a role in visual communication during the night,” Graipel wrote.
“The absence of white marks in a melanistic individual tends to be a limiting condition for intraspecific visual communication at night, resulting in an evolutionary dilemma for these species, that is, to be almost invisible at night, but not to communicate visually.”
The study estimates that the disruption in communication could make it harder for melanistic cats to survive in the wild; if a non-melanistic leopard gives birth to a panther, it could be difficult for the baby panther to follow its mother’s cues and vice versa. This could lead to an increased death rate in infant panthers, making the trait even rarer.
There is also a possibility that the panther’s dark coat is caused by genetic drift, a variation in the frequency of different genotypes in a given population due to certain traits disappearing when their carriers fail to reproduce.
Dr. Greg Barsh, with the HudsonAlpha Institute for Biotechnology, delved into this concept with Smithsonian Magazine.
He explained that while Graipel and his colleagues fielded some interesting inferences, their hypotheses are difficult to test due to the panther’s elusive nature.
Still, he agreed that some of their theories are supported by compelling evidence.
“I think the strongest and most interesting observation is that species in which melanism is found also tend to be species that have white marks on their ears,” he said—a fact that has experts intrigued and warrants further study.