At the Zoo: The Snorting Gazelle
by Debra Solomon
John
Hanning Speke (1827-1864) was a British explorer most famous—and
infamous—for his lifelong quest to find the source of the
Nile. In 1858, Speke declared East Africa's Lake Victoria
the Nile's source and returned to England a hero—only to
find that his colleague and fellow explorer Sir Richard Burton
challenged his claim. On the day Speke and Burton were to
debate the issue in public, however, Speke died while hunting,
apparently killed by his own gun.
In spite of the cloud surrounding Speke's claim, his discovery was quickly confirmed after his death. But finding the source of the Nile wasn't the only legacy Speke left. He also left his mark on the names of several East African animals he was first to describe to the West, including Speke's weaver, a small bird, and Speke's gundi, a rodent.
One of Speke's most graceful "finds" was Speke's gazelle, four of which recently arrived at the National Zoo, where they now live at the Cheetah Conservation Station. Small and delicate, Speke's gazelles are brown, dog-sized antelope with white patches around the bases of their tails and on the backs of their thighs. They are found in the wild on the dry open plains of Somalia and Ethiopia. Adapted to a desert climate, they feed in the morning and evening, when leaves hold the most moisture, and lie around during the hottest times of the day, conserving precious water.
Speke's gazelles have an odd but distinctive trait: When they get scared or nervous, they inflate the skin on the tops of their muzzles, amplifying the already loud snorts they use to alert one another of danger.
In Africa, poaching and hunting, as well as agricultural development and over-grazing by domestic animals, threaten Speke's gazelles. The political situation in Ethiopia and Somalia in the 1980s prevented accurate population counts and led Westerners to believe that Speke's gazelles were virtually extinct, although in reality they were only threatened in the wild, with perhaps as many as 1,000 remaining. Under the impression that extinction loomed, zoos in the West developed plans to increase their Speke's gazelle numbers, ultimately to produce animals that could breed with the few wild Speke's gazelles left in East Africa.
At that time, the St. Louis Zoological Park had the only breeding population of Speke's gazelles in North America, one male and two females imported in 1969, and a female bought in 1972 from the Lincoln Park Zoo in Chicago. By 1983, other zoos, including the Gladys Porter Zoo in Brownsville, Texas, and the San Diego Wild Animal Park, had several Speke's gazelles, all offspring of the four animals in St. Louis.
Keepers at the St. Louis Zoo in the 1980s saw a familiar pattern among the Speke's gazelle population: low birth weights and steadily decreasing levels of fertility and viability that are typical of inbred populations. Inbreeding depression used to be a common problem in zoos, especially in small populations of rare or endangered animals.
To avoid inbreeding depression and to develop a healthy zoo population, the American Zoo Association (AZA) instituted a series of Species Survival Plans (SSPs) to monitor and manage threatened species in zoos. Zoos across the country work together to increase the size and diversity of the founding populations and interbreed the animals in order to maintain high levels of genetic diversity.
The small number of Speke's gazelles in North America and the lack of available wild animals made the gazelle's case particularly difficult. With such a small founding population, zoos found themselves unable to avoid inbreeding.
Some studies had shown, however, that small founder populations could adapt quickly to inbreeding. So the St. Louis Zoo undertook an intensive program to adapt their Speke's gazelles to inbreeding. They bred the animals quickly, increasing numbers as rapidly as possible in an attempt to eliminate—through death—the deleterious genes from the population. The program, a risky attempt at genetic management, was a success. In a few years the zoo population of Speke's gazelles nearly doubled, while all signs of inbreeding depression disappeared in two to three generations.
By 1991, the Speke's gazelle population in zoos reached an all-time high of 40, but shortly thereafter the population began to suffer again, dipping to 24 individuals by 1994. The St. Louis Zoo imported two females from Qatar to diversify the gene pool, a strategy that seems to have worked. As of December 1996, five institutions in North America house a total of 35 Speke's gazelles.
With the acquisition of the Speke's gazelles, the Zoo joins its 39th Species Survival Program. The four Speke's gazelles now at the National Zoo are graceful—albeit snorting—examples of the Zoo's strong commitment to the conservation of threatened species.
(ZooGoer 26(1) 1997. Copyright 1997 Debra Solomon. All rights reserved.)
