Stars in Stripes
The sound of thundering hooves heralds a herd of zebras. Galloping along at up to 35 miles per hour, these striped steeds can cover plenty of savanna in a short time. At first glance they may all look alike, but each zebra has a unique stripe pattern—no two are the same.
There are three species of zebra: plains, mountain, and Grevy’s. Plains zebras and mountain zebras are considered threatened and near vulnerable, respectively. Weighing up to 1,000 pounds, the Grevy’s zebra is the largest and considered an endangered species.
Survival Isn’t Black and White
Recent estimates put the remaining wild Grevy’s zebra numbers at fewer than 2,500 individuals, and today they can only be found in the arid grasslands of southern Ethiopia and northern Kenya. They once inhabited much of East Africa, including Somalia, Ethiopia, Eritrea, Djibouti, and Kenya, but in the last 30 years their population has decreased by more than 50%.
For many years, all zebra species were heavily poached for their beautiful striped skins, but more recently they have been affected by severe, rapid habitat loss. Zebras graze on wild grasses and plants, but as more land is developed for livestock and crops, and natural water sources are re-routed for irrigation, zebras are dying more frequently of starvation and thirst. However, the most serious threat to wild zebra populations is actually disease.
Zebras are vulnerable to tick-borne illnesses transmitted by livestock animals with whom they share land. While livestock are vaccinated against many diseases, wild animals aren’t. The most deadly sickness for zebras is an anthrax infection, outbreaks of which have decimated their populations.
Anthrax is a naturally-occurring bacteria. In some parts of Africa, it’s so common that it’s considered part of the natural ecosystem. Unfortunately, once an animal has been exposed to the bacteria, it dies within a few days. Anthrax prevents blood from clotting and thins it so much that it seeps out of the infected animal.
The anthrax bacteria is hardy, withstanding freezing and boiling temperatures, and can survive in the soil and on vegetation for decades. Zebras ingest the bacteria when grazing on grasses and plants. After it enters an animal, anthrax begins its maturation, thinning the animal’s blood. When the host animal dies, the bacteria returns to the soil during decomposition. Growing plants benefit from the nutrients deposited into the ground by the decaying animal. These lusher, greener grasses are more appealing to herbivores than other vegetation, which serves as a lure to continue the deadly cycle.
Holding the Line for Zebras
San Diego Zoo Global supports the Grevy’s Zebra Trust, an organization in Kenya dedicated to the survival of Grevy’s zebras in the wild. Our scientists also work with other conservation groups to help preserve zebra populations and monitor their numbers, and we partner with communities in Kenya to vaccinate zebras against anthrax.
Here in San Diego, we have welcomed nearly 300 zebra foals, representing all three species, into our herds at the San Diego Zoo and San Diego Zoo Safari Park. These charismatic animals bring conservation to life for guests and inspire them to care about these stunning striped steeds of the savanna.