Horse of a different stripe

Press, 13 June 1984, Page 19

Horse of a different stripe

They are black and white; have large, rounded ears; can weigh up to 360 kilograms; and are sometimes hard to find, even in daylight. But they are also a fastdisappearing species in any light, known as Grevy's zebra and now living only in pockets of Kenya and Ethiopia.

Unlike common zebras, which gather in great herds on the east African plains, Grevy’s zebras spread out over their arid habitat. And when a small group does form in the shade of a tree, it blends in like a soldier wearing camouflage. “The Grevy's zebra has very fine stripes,” says Dr Joshua Ginsberg, aged 25, of Princeton University, who is studying the animals. “It’s like looking through a window screen, especially in heat haze. The stripes really move.” After 1200 hours of "reading between the lines” — peering at the animals through binoculars and tracking them through two of Kenya’s game reserves — Ginsberg knows a Grevy's zebra at a glance. He is accustomed to what he calls their Mickey Mouse ears, and he is beginning to appreciate the complex social organisation of this little-studied species. Half again as big as the common, or plains, zebra, the Grevy’s variety also has a much more intricate stripe pattern, which makes it irresistible to poachers with visions of zebra-skin coats and purses.

The stripes also serve as a ready-made identification system for the scientist, whose work is supported by the National Geographic Society. Like the uniqueness of a human thumbprint, each individual zebra has its own stripe pattern, most easily distinguished on the Grevy’s rump. So Dr Ginsberg observes many of his subjects from behind.

Using these dashes, crosses, Vs, and Ys, he has identified 520 individuals. He had to turn to a baby book to find enough names. He ’ also borrows from friends; Nancy and Alison, a mare and her foal, were named for his supervisor’s wife and daughter.

One of the world’s three zebra species, Grevy’s zebra (Equus grevyi) got its name from Jules Grevy, a president of France who received one of the animals in 1882 as a gift from Ethiopia. Once widely distributed over northern Kenya, Ethiopia, and Somalia, the

zebra has been hunted to extinction in Somalia and is losing ground elsewhere. Only 8000 to 10.000 are thought to exist, and habitat destruction threatens them. The zebra was placed on the endangered species list four years ago. Dr Ginsberg's months in the field have provided glimpses of zebra behaviour not apparent to the tourists who zip through in vans. Besides grazing and sleeping (which they do standing up. knees locked and eyes often open), the animals hit the ground to "dust bathe.” They gather at the baths once or twice a day. flopping down and rolling, to cool off and rid themselves of parasites.

One encounter made all the sacrifices of living out of a Landrover worthwhile for Ginsberg. He and his assistant had been following a zebra group around the jagged remains of a lava flow when they spotted a lone female Grevy's zebra. It was Christine, a mare known to be pregnant. When the zebra saw the humans, she went on the defensive. Her ears shot forward, a sign of alarm, and she stared fiercely ahead, stomped her foot, and snorted, a departure from the usual hee-haw.

Ginsberg, climbing on top of the vehicle for a better view, then saw the reason for the fuss: a tiny, minutes-old zebra lay in the dusty grass. Deciding the people were no threat, Christine began to lick her foal.

Within an hour, the foal had put its shaky legs to the test, finally with success. Then, two hours into the foal’s life, the mother suddenly took off, possibly in search of water, contradicting data showing that zebra mares never leave their newborn. The foal spent the rest of the day sleeping alone, the high grass shielding it from predators’ view. The next day Christine and her foal were sighted in the “kindergarten,” a group of offspring under the care of a mare or stallion.

What most interests Dr Ginsberg is the Grevy’s zebra's social system, known to be different from that of the common zebra. Like horses, common zebras form harems with a male, several females, and their foals in a permanent bond. But male Grevy’s

zebras use a system of territories instead.

The territory — at 2 square miles, the largest of all — is held by a stallion that asserts rights to breed with any sexually receptive female that ” wanders through. Other males can graze freely in a territory, as long as they do not attempt mating. Within a territory

are foals and their mothers, which mate with the stallion about a week after giving birth. The other major study of Grevy’s zebras showed them to form only temporary groups, the only permanent bond being between a mare and a foal. But Dr Ginsberg has observed groups of mares and foals that stay together as long as four months within a male’s territory. This variation may be a response to this group’s own peculiar habitat.

“Horses change their social organisation in different habitats; why not zebras?” Dr Ginsberg asks. “Why do they form these groups?” he wonders. “Do the foals then associate as yearlings? Do they return to the same area when it’s time for them to breed?”

He will be pursuing the answers, from close behind, in this year’s field season.

By

BARBARA MOFFET,

National Geographic

News Service