There are a few things that we know for certain about the animal kingdom. For instance, bulls always have two horns (except this three-horned cow), puppy tails are found on the animals' rear (except for this "unicorn" puppy), fish can only survive in water (except for this "snakehead" species), and tarantulas absolutely cannot swim (except for the ones that can).
OK, so maybe the animal kingdom still has a few surprises up its sleeves. But at least we can take solace in the certainty that zebras will always have stripes, right?
Enter a photograph supposedly showing a zebra that was born with "polka dots" instead of stripes:
This is a genuine photograph of a zebra born at the Masai Mara National Reserve in Kenya in 2019.
The zebra was named Tira after Antony Tira, a tour guide and photographer at the reserve who first spotted the rare animal.
Tira told the Kenyan outlet Daily Nation, "At first I thought it was a zebra that had been captured and painted or marked for purposes of migration. I was confused when I first saw it."
Ren Larison, a biologist studying the evolution of zebra stripes at the University of California, Los Angeles, told National Geographic that Tira has a condition called pseudomelanism. This genetic mutation can cause abnormal stripe patterns:
Specialized cells called melanocytes produce melanin, the red, yellow, brown, or black pigment that determines hair and skin cell color in mammals.
“There are a variety of mutations that can disturb the process of melanin synthesis, and in all of those disorders, the melanocytes are believed to be normally distributed, but the melanin they make is abnormal,” Greg Barsh, a geneticist at the HudsonAlpha Institute for Biotechnology, says by email.
In zebras, melanocytes are uniformly distributed throughout their skin, so that a shaved zebra would be completely black. In the case of Tira and other pseudomelanistic zebras, Barsh believes the melanocytes are all there, but the melanin itself, for some reason, does not manifest correctly as stripes.
National Geographic photographer Frank Liu posted a few additional photographs of this polka-dotted zebra to his Instagram page along with this video:
Tira is not the only zebra with this rare condition. In 2014, for instance, a similarly spotted zebra was photographed in Botswana.
In September 2019, shortly after the photographs of Tira went viral, Dr. Cliff Bull, the owner of the Craig View Veterinary Clinic, shared a set of images to Facebook which showed him with a different spotted zebra in South Africa:
The Craig View Veterinary Clinic wrote:
Dr Cliff Bull was recently asked to dart and work with a Zebra Colt with the same mutation called Pseudo Melanism which is when an animal with a patterned coat has more pattern than usual. This often occurs a in big cats but you can read more about it on @anatomika.science great post about it!
A couple fun facts about Zebra:
1- Zebra are in fact black with white, recent research through embryological evidence shows that the zebra’s underlying colour is actually black and that the white stripes are added on top.
2- Their stripes have evolved to keep the biting insects away- the monochrome pattern seems to throw off the visual systems of flies.
3- A zebra’s stripy coat prevents the animal from overheating in the African sun. This is because air moves at different speeds over light-absorbing black stripes and light-reflecting white stripes, so the zebra creates its own cooling air currents.
This Colt pictured below with Dr Bull and his family group were successfully relocated!
IFL Science writes that zebras with this condition may be at some disadvantages in the wild. For instance, a zebra's stripes are believed to help protect it from horsefly bites. Tira's unique look may also make it easier to spot by predators:
While the polka dot pattern is certainly peculiar, melanistic zebras are not unusual. Zoologist Professor Jonathan Bard first described such a case in 1977, where an individual also had a spotted pattern. The extent of melanism is a spectrum, and in zebras, it can present as peculiar patterns. At least they look that way to us. To zebras, all patterns look different.
Zebras recognize each other by their markings, which are unique for each animal, like human fingerprints. In fact, there are actually three species of zebra, each with their own distinct markings ranging from stripe patterns to which part of the body is covered. The stripes are believed to be not for camouflage but instead a way to ward off horsefly bites, which are both dangerous and annoying.
Without stripes, Tira may have to worry about more than horseflies though. Melanistic zebras tend to stand out more clearly from the herds, and especially when they're young, it may make them easier targets for lions and hyenas living in the savannah.