This could eventually lead to new subspecies of plains zebra. In other words, zebras are becoming genetically closer within their populations, but these populations are growing more distant genetically-mirroring their physical separation. “We found that there are populations that are possibly diverging more than they would under normal circumstances, because of human population pressure,” says Larison, whose work is supported by the National Geographic Society.

( See pictures of a white giraffe and other unusually pale animals.)

For their analysis, Larison and her colleagues used advanced genetic sequencing techniques to closely study differences between not only inbred zebras, but also the zebra populations in distinct locations.

The more immediate concern, she says, is the plains zebra’s genetic health. Within their family groups, however, zebras don’t much seem to mind who’s striped and who’s spotted, notes Larison, whose latest research suggests zebra stripes help the animals avoid biting flies. It’s possible odd stripes could make the zebras more obvious to predators for instance, most recorded instances of polka-dotted zebras are as foals, not adults. “Even though plains zebras aren’t highly threatened, these genetic issues often show up before really problematic things start happening,” she says.Ī foal with pseudomelanism, a rare genetic mutation in which animals display some sort of abnormality in their stripe pattern, drinks from a water hole in Namibia's Etosha National Park in November 2011. While the study only looked at seven animals with odd patterns, the results could be a visual warning about the plains zebra’s future, says Larison. But the study also revealed these isolated groups were more likely to produce abnormally striped zebras, suggesting these genetic mutations are caused by their poor genetic diversity. Their study, published recently in the journal Molecular Ecology, found that smaller, more isolated populations of zebras had lower genetic diversity-not a surprise. To find out, Larison and colleagues ran genetic analyses on 140 individual plains zebras-including seven animals with unusual coat patterns-from nine locations in Africa, including Nambia’s Etosha National Park and South Africa’s Kruger National Park. ( Read more about Larison’s research in her own words.) “The observation led me to wonder: Is part of the reason that I’m seeing so many is because this population is inbred?” says Larison, who studies the evolution of zebra stripes at the University of California, Los Angeles. A lack of gene flow can lead to inbreeding and ultimately infertility, disease, and other genetic defects. Migrating infuses populations with new genes, making it key to a species’ long-term survival. Habitat fragmentation caused by fences, roads, and human development have squeezed zebra populations, like the one in Lake Mburu, into small pockets of land, preventing some of the animals from migrating between herds. Though plains zebras are the least threatened of the three species, their numbers have dropped by 25 percent since 2002, with around 500,000 animals ranging from Ethiopia to South Africa. So biologist Brenda Larison found it striking that an unusually high number-an estimated 5 percent-of plains zebra living near Uganda’s Lake Mburo were abnormally striped. Such aberrations-often caused by genetic mutations that alter the production of melanin, a natural pigment-are generally rare among mammals. In 2019 in Kenya’s Masai Mara National Reserve, scientists recorded a polka-dotted foal, with white spots covering its dark-brown body.

But in some cases, these African equines sport unusual color patterns, such as large, black splotches or golden coats with light-colored stripes. Anyone can tell you that zebras have distinctive black and white stripes.

Spotted zebra butterfly