The surprising reason zebras have stripes - Cella Wright
When an English aristocrat rode
through London in a zebra-drawn carriage,
he embodied a dream decades in the making,
borne from European efforts to dominate
the African continent.
But 19th century European colonists
faced big problems
as they tried to control the sprawling
African territories they’d claimed,
one of which was biting flies.
These pests could extract half a liter
of horse blood daily
while transmitting fatal diseases
that devastated domestic horses,
leaving colonial powers reliant
on thousands of humans to transport goods.
Zebras, however, appeared immune
to the same pitfalls as horses.
The German Empire deemed them “predestined
for the use of military needs,”
and undertook the task
of domesticating them.
Around 1900, former German colonial army
officer Fritz Bronsart von Schellendorff
placed himself at the mission’s helm.
But he severely underestimated
the project.
And soon enough,
the question of why domesticating zebras
was proving so difficult
joined another longstanding mystery:
namely, why zebras had such
conspicuously striped coats—
a matter that perplexed
prominent scientists—
and went on to fuel decades of debate.
To understand zebras’ more
distinctive qualities,
we should start with the big picture.
Zebras belong to the same family
as horses and donkeys.
After their lineage entered Africa,
they evolved into the three zebra
species that exist today,
living in social herds in eastern
and southern Africa,
grazing on grasses
and evading fierce predators.
Scientists have speculated extensively
about zebra striping,
but not all theories have held up.
For example,
the hypothesis that striping has a social
function seems unlikely because,
while every zebra does
have unique patterning,
other equids have no trouble identifying
individuals in their herd without it.
Some have theorized that the pattern helps
zebras stay cool in direct sunlight,
with the heat differential
between their black and white stripes
generating cooling air currents.
But when scientists tracked the air
movements around sunlit zebra hides,
they saw no such effect.
Many have also wondered if the patterning
works as camouflage
or somehow confuses or dazzles predators—
perhaps evoking a tangle of tree trunks
or creating uncertainty around where
the zebra’s body starts and ends.
But hyenas and lions probably see zebras
as gray until they're in close range,
where they can also hear and smell them.
Lions can likely also identify their
outlines just as easily as they can
other, less flamboyantly patterned prey.
And given how frequently
lions capture zebras,
it doesn't seem like they're
all that confused.
One hypothesis that does
pack a lot of promise
concerns those biting flies
that horses couldn’t handle.
Zebras have shorter hair than other
grazers in their regions,
possibly making them more vulnerable
to the flies’ probing proboscises.
So, perhaps striping somehow
acts protectively.
Testing this hypothesis,
one experiment found that a certain kind
of biting fly
avoided horses covered in striped
and checked rugs,
compared to those in solid grey.
Another documented biting flies
circling horses, zebras,
and horses clad in zebra print equally—
but landing on zebra-y areas
only about a quarter as much.
Biting flies also generally approached
zebras at higher speeds
and didn't decelerate as usual,
causing clumsy overshoots
and crash landings.
It seems that zebra stripes—
and other graphic patterns—
interfere with how biting flies
process visual information
to position themselves when landing,
limiting their blood-sucking
and disease-transmitting opportunities.
But zebras aren't just good at keeping
biting flies off their backs.
Around 1900, Bronsart founded an
experimental ranch near Mount Kilimanjaro
to capture and cross-breed zebras
with other equids.
Things didn’t go as planned—
in part because zebras have a robust set
of defensive fight and flight adaptations.
Most are capable of running
within an hour of birth,
and they’re equipped with fierce bites
and kicks strong enough to kill a lion.
Bronsart’s operation was also unprepared
to meet zebras’ needs.
Those Bronsart did gather, which he
paid Indigenous people to wrangle,
couldn’t produce enough milk
for their calves.
Within a single year, Bronsart had burned
through a five year budget
and dozens of the zebras he held
in captivity were dead.
Attempts at zebra domestication
had failed miserably,
leaving those rare instances of zebra
taming largely to black-and-white history.
