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Wild zebra, asses and horses are being killed for meat, medicine and money. Combined with vanishing habitats and naturally slow reproduction, such predation threatens remaining populations
AFRICAN WILD ASSES pause on a rocky slope in Eritrea. These young males display the unique pattern of leg stripes that allows researchers to identify individuals.
FROM THE TIME OUR ANCESTORS FIRST PAINTED ON CAVE WALLS, the beauty and speed of horses have captured our imagination. During this period, some 20,000 to 25,000 years ago, equids were among the most abundant and ecologically important herbivores on the grasslands of Africa, Asia and the Americas. Today only seven species of wild equids remain—three asses, three zebra and one wild horse—
and IUCN-The World Conservation Union now lists most of close to one another or to form consistent groups. Each adult these as endangered [see box on opposite page].
Wildlife biologists, including the Equid Specialist Group of the IUCN, which I chair, study the dwindling populations to learn as much as possible about these historically important animals while they still roam free. We also search for ways to stem their disappearance and have recently developed a plan that prioritizes the actions that should be taken.
Two Styles of Life our work, which builds on that of an early researcher, Hans Klingel of the University of Braunschweig in Germany, distinguishes two distinct patterns of social organization in wild equids. All the animals live in open lands, but their habitats can range from arid desert to grassy plains favored by moderate rainfall. It is the ease of obtaining food and water that determines how these potentially gregarious animals organize themselves for foraging and for mating and rearing their foals.
In the grasslands, such as the Serengeti Plain of Tanzania, abundant forage and water allow females to feed together and thus to form stable groups. A male that can block other males from access to this group gains exclusive mating rights with all the females, and thus this system is referred to as a "harem" or "family." In dry environments, such as the Danakil Desert of Ethiopia and Eritrea, the scattered supply of food and limited water usually do not permit females to forage
Overview/Equid Conservation is on its own to find nourishment, and a male will establish a territory near a critical source of water or food; he then controls mating rights with all females that come onto the territory to drink or feed.
In the harem type of organization, groups usually consist of one adult male and one or more females and their offspring. Other males live in "bachelor" groups. The adult females often remain together throughout their lives, but the harem stallion may be displaced by another male, depending on his age and fighting ability and the number of competitors he has to contend with. Foals born into a group stay with it for two to three years before they disperse. Young females usually leave during their first estrus and join other families. Young males tend to stay on for several more years before they depart to find bachelor groups.
The harem strategy, generally followed by plains and mountain zebra as well as by feral horses, often provides a relatively safe environment in which mothers and their foals can thrive. The presence of the dominant stallion markedly reduces harassment from bachelor males, which might otherwise chase and attempt to copulate with the females. Such harassment can be deadly: it hinders the females' ability to feed and can end in abortion or even infanticide. Stable groups and the presence of the stallion also help to fend off predators such as wolves, lions and hyenas.
By contrast, in dry environments, the only long-term assemblages are a female and her offspring, sometimes just a foal, sometimes a foal and a yearling. No permanent bonds persist between adults, although they sometimes form temporary groups. African wild and feral asses, Grevy's zebra and Asiatic wild asses organize themselves in this more socially ephemeral way, with a dominant male controlling a territory near a critical resource. The territorial stallion can dominate his area for years. He tolerates both males and females on his land, but he alone can mate with any female that ventures into his realm.
Controlling access to water is critical. Lactating females need to drink at least once a day, and so they will stay as close to a pond or stream as possible. A female comes into estrus a week or two after giving birth and, if she is not fertilized then, again about a month later. Thus, the territorial male has several
■ Wild horses, asses and zebra were once one of the most abundant herbivores in Africa and Asia. Now only seven species remain, and most of these are endangered.
■ Human populations, themselves struggling to survive, can be their greatest threat, killing them outright and encroaching on their habitat.
■ Extinction is a real possibility for these endangered animals because wild equids reproduce slowly.
■ Researchers are stepping up efforts to learn about the animals' way of life and are seeking ways to conserve them in their natural habitats.
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