By Maymie Higgins
The cheetah’s shoulders arched upward like a ready arrow in a fully drawn bow. With head low and eyes forward, he hoped the thick morning fog over the savanna would work in his favor. His last meal was a mere rodent and days ago. He studied the grazing herd, waiting for an individual to linger as the rest of the herd moved away. He and his brother’s coordination with one another would be crucial. Today, it was this cheetah’s turn to subdue the prey as his brother isolated it from the herd. Suddenly, his brother bolted and startled an isolated doe and her fawn. The fawn darted into the herd, reflexively lifting its tail, revealing a flash of white fur and releasing a scent that signaled the herd to flee swiftly and en masse. The doe darted too, keeping pace with the herd, albeit 50 yards behind as the cheetahs flanked her, accelerating to 60 mph to remain parallel. They drew in closer and the attacking cheetah leapt, his claws grazing the doe’s haunches, but failing to apply full weight and subdue her. Neither cheetah could again accelerate to the speed at which the doe ran. These hungry cheetahs were not African Cheetahs (Acinonyx) on the Serengeti but rather the now extinct American Cheetah (Miracinonyx) in the Pleistocene Great Basin. Their extinction may be due to losing participation in an evolutionary arms race for speed. The winner? The pronghorn (Antilocapra americana), who, in modern times, is the only extant member of the family Antilidocapridae; a family that originally had 12-13 members.
The pronghorn story is a success story, with caveats. Fossil records for pronghorn go back to the Miocene. In the 1800s, there were 35 million pronghorn in North America. By 1924, they were near extinction with only an estimated 20,000 remaining due to expansion of the nation and its effects from events such as overhunting and erection of fencing (pronghorn actually don’t jump very well) for domestic livestock that interrupted migration patterns. Human development and drought continue to pose threats in their current range. Pronghorn occupy tall and short grass prairies and deserts.
Pronghorn are of ecological importance because they eat noxious weeds and invasive plants which help to protect the cattle, bison, sheep and horses with which they share range. They also fill a niche in the ecosystem between deer and sheep and promote growth of native vegetation by grazing on plants such as Adam’s tree (Fouquieria diguetti), brittlebush (Encelia spp.), elephant tree (Pachycormus discolor), spurge (Euphorbia leucophylla), cliff spurge (E. misera), desert hollyhock (Sphaeralcea ambigua), thorn bush (Lycium spp.), saltbush (Atriplex spp.), Aristida aristidoides, and Phaseolusfiliformis.
Besides the importance of pronghorn to the ecosystem, their mere existence is thrilling. It is exciting that there remains an ungulate in North America that is not only one of a kind, but who also has physical adaptations to outrun predators that have not existed for thousands of years! They are capable of incredible speed because of an oversized windpipe, large lungs and a large heart. Pronghorns run with their mouths open to foster intake of oxygen, of which they require three times more than other similarly sized animals. They have more mitochondria in their muscle cells for power and padded hooves to withstand terrain at high speeds. There are tales (perhaps of the tall variety) of pronghorn racing horses and trains for sport, with one report citing in excess of 80 mph. They are the fastest land mammal in the Western Hemisphere. They are the second fastest land mammal in the world behind……you guessed it…..the African cheetah.
There are now an estimated 700,000 pronghorn in the wild, with recovery achieved from establishment of hunting restrictions and habitat protection. But there are two subspecies of pronghorn, the sonoran pronghorn (Antilocapra americana sonoriensis) and the peninsular pronghorn (Antilocapra americana peninsularis), that have required cooperative recovery efforts to prevent extinction. Both of these subspecies have the assistance of U.S. zoos in propagation and technical assistance with herd management.
The sonoran pronghorn is now estimated to have a wild population of 200-800 between U.S. and Mexico, but their population had dwindled down to a mere 21 in 2002 following a severe drought. Mexican populations have been listed on the Endangered Species List since 1967, and are also listed on the IUCN CITES Appendix 1. In 2003, the U.S. Fish and Wildlife Service partnered with biologists in several zoos, including the Los Angeles Zoo and San Diego Zoo, and with the Mexican government to begin a captive breeding program. Seven sonoran pronghorn were captured for a captive-breeding program and a square mile of desert was set aside at Cabeza Prieta National Wildlife Refuge, just north of the Mexican border, to hold the captive animals. Water guzzlers and supplemental food was provided within the enclosure and the pronghorn were protected from predators such as coyotes and mountain lions. These pronghorn successfully reproduced and the captive population grew. In 2006, the refuge began releasing some of the young males. The captive-reared sonoran pronghorn were able to integrate well with the wild population. So far, 91 sonoran pronghorn have been released into the wild and as of December, 2012, the overall wild population of sonoran pronghorn is estimated to be at 160 animals and growing. Also since 2006, captive-bred sonoran pronghorn, some from U.S. zoo propagation programs, have been released into the wild across several different sites in the U.S. and Mexico, including Barry M. Goldwater National Wildlife Refuge, Organ Pipe Cactus National Monument and Kofa National Wildlife Refuge.
The peninsular pronghorn is one of the most endangered large mammals in Mexico today, with a wild population lingering around 200, and is listed as critically endangered by the IUCN. The Mexican government, the Los Angeles Zoo and a sponsorship by the Ford Motor Company have implemented an in situ recovery program within El Vizcaino Biosphere Reserve (VBR) on the Baja California Sur peninsula. In 1997, the estimated population of peninsular pronghorn was 170. From 1998 to 2003, a total of sixteen wild fawns, which were hand-reared, and nine wild adults were captured to form a founding captive herd. This herd is protected within an elaborate fenced area with outer measurements of 1,400 x 1,850 meters and inner features such as moveable fences. There were challenges but by 2003, there were 85 births and only 20 deaths in the captive herd. Today, there are 250 adults and 40 young pronghorn in the captive population. The captive peninsular pronghorn are used to supplement the wild peninsular pronghorn population and maintain wild population genetic diversity.
The pronghorn story is just one of many examples of how biologists, veterinarians, keepers and aquarists at zoos and aquariums throughout the world are collaborating with governmental organizations, non-governmental organizations and even corporations to conserve and preserve the natural world.
All photos are of sonoran pronghorn and obtained from the United States Fish and Wildlife Service website http://www.fws.gov/faq/imagefaq.html)