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| © Photograph by Frank Liu Tira, the spotted zebra foal, may be more suspectible to biting flies without the zebra's trademark stripes. |
Talk about a horse of another color—a zebra foal with a dark coat and white polka dots has been spotted in Kenya’s Masai Mara National Reserve.
Photographer Frank Liu was on the search for rhinos recently when he noticed the eye-catching plains zebra,
likely about a week old. “At first glance he looked like a different
species altogether,” Liu says. Antony Tira, a Maasai guide who first
spotted the foal, named him Tira.
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| © Photograph by Frank Liu Tira walks through Kenya's Masai Mara National Reserve with her mother in a recent photograph. |
Zebra stripes are as unique as fingerprints, but Tira’s odd coloration
could be the first recorded observation in the Masai Mara, according to
Liu. Similar foals have been seen in Botswana’s Okavango Delta.
Tira and these other foals have a condition called pseudomelanism, a
rare genetic mutation in which animals display some sort of abnormality
in their stripe pattern, says Ren Larison, a biologist studying the evolution of zebra stripes at the University of California, Los Angeles.
Zebras also experience other unusual color variations, such as partial albinism, which was seen in an extremely rare "blond" zebra photographed earlier this year in Tanzania’s Serengeti National Park.
Keeping track of such equine aberrations is useful to science as part
of a broader goal to monitor changes in species and how they’re managed
by local communities.
Showing their stripes
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. (Learn more about why animals are black and white.)
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.
Tira’s future is likely uncertain—most
zebras with such unusual coloration probably don’t survive long, Larison
notes. “Research on other species has shown that, while it is harder
for a predator to target an individual in a group, it is easier if an
individual is different,” she says. (Read about a rare white giraffe and other unusually pale animals.)
“I
have seen several photos of foals with this specific pattern over the
years, but only one photo—from the ‘50s—in which the individual was
either a juvenile or adult.”
Hurdles to survival
Unfortunately for Tira, recent research by Larison and others has suggested that zebra stripes evolved to deter against biting flies—one
of five theories that have been posed over the years, along with
camouflage and temperature regulation. Experiments in the field, for
instance, have shown that biting flies don't like landing on striped
surfaces.
If that’s the case, Tira won’t be as successful at
repelling these flies—which can carry diseases like equine influenza—as a
normally striped zebra, notes Tim Caro, a biologist at the University of California, Davis. (See a photograph of a rare black leopard photographed in Africa.)
However, if Tira can survive these many hurdles and make it to adulthood, there’s no reason to think he can’t fit into the herd.
Research conducted in South Africa has found that in two cases of plains zebras with aberrant coloring, at least, the animals formed normal relationships with other zebras—including mating.
