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Pronghorn Antelope The Antelope That's Not Really an Antelope... Article by ryan o’shaughnessy, research scientist Photos by james weaver, tpwd

Male pronghorns in typical southwest desert habitat.

ronghorns have accrued a variety of the old world. in other words, they resem- pronghorn are similar to those of a true an- of diff erent names over the years, ble the antelope species of africa, and they telope. each horn has a core of bone that is including prong buck, cabri (Native tend to occupy similar ecological niches. in covered by a keratinous sheath. despite the american),P speed goat or simply antelope. fact, the closest living relatives of pronghorns structural similarity in the horns of a prong- although it is commonly claimed that prong- are giraff es. Key attributes in the biology and horn and true antelope, the annual cycle of horns are the only North american species of the behavior of the pronghorn make this spe- horn production in pronghorns is analogous antelope, the name antelope is somewhat of a cies unique, not just to the plains of North to deer. each year, pronghorns will shed and misnomer. Pronghorns are, in fact, not true america, but also in the context of diversity regrow the keratinous shed of the horn. Th is antelope; but, then again, they’re not deer of all free roaming ungulates worldwide. cycle is likely to be an evolutionary adaptation either. But if they’re diff erent from antelope, one of the fundamental defi ning attributes to the temperate climates of North america. why do we call them antelope? well, prong- of pronghorn is its horns. Pronghorns share like deer, that shed their antlers each year, horn are oft en mistakenly designated as ante- characteristics of horn development with pronghorns likely shed the horn sheath each lope, because they resemble the true antelope both true antelope and deer. Th e horns of a winter in an eff ort to conserve energy by re-

22 TEXAS WILDLIFE JUlY 2014 borderlands news ducing the weight of the head. But, unlike deer and similar to antelope, the cen- tral bone core of the horn is retained throughout the year. Conversely, prong- horn horns are branched, resembling simple deer antlers, whereas horns of true antelope are always unbranched. Both male and female pronghorns can car- ry horns, although they are typically larger and more developed in the males. Similar to many spe- cies of antelope and deer, pronghorns are ruminants, which means they chew their own partially digested food. By doing this, they Mixed herd foraging on grassy plains. are able to break apart food particles into smaller and smaller pieces thereby maximizing the nu- ning. Pronghorns are said to be the fastest reproductive differences. The average female trition gained from the vegetation on which land mammal in North America. Unlike deer pronghorn will gestate for approximately six they feed. Pronghorns will commonly feed or antelope, which are able to run quite fast weeks longer than the average white-tailed on forbs, shrubs, grasses and even cacti. over short distances, pronghorns are able to deer. The seven to eight month gestation Pronghorns eat a wide variety of plant foods, maintain high rates of speed over long dis- period in pronghorns is longer than what is including species that are toxic and unpalat- tances. Since the speed of pronghorns far out- typical for most North American ungulates, able to other animals. The kidneys in prong- paces any predator in North America, it is be- and it is longer than most similarly sized an- horns are quite large compared to deer and lieved that the pronghorn evolved its running telope. The longer gestation period likely ac- antelope, and this adaptation is likely to help ability to escape extinct predators such as the counts for the high prevalence of twin fawns remove toxins in many plant species that are American cheetah. Compared to deer and in pronghorns. Twinning occurs in over 94 poisonous to livestock and other ruminants. antelope, pronghorns have certain physio- percent of pronghorn births. The enlarged kidneys may also play a role in logical traits which allow them to run at great Many people may claim that the bison is reducing the need for water in pronghorns. speeds over great distances. Some of the more the iconic species of the American West, but Since they extract most of their water from obvious adaptations include enlarged lungs, the pronghorn has every right to stake its own the vegetation on which they feed, prong- heart, and windpipe which allow pronghorns claim to that title. The unique taxonomy, cha- horns are less dependent on water com- to take in large quantities of oxygen to power risma, reproduction and sheer speed of this pared to white-tailed deer and mule deer. An muscles while running. Another adaptation animal set it apart from all others. To incor- anatomical difference in digestion between for speed is the somewhat smaller stomach rectly classify the pronghorn as an antelope or pronghorns and deer is the presence of a gall- compared to other species. Less obvious ad- deer detracts from its charm and its contribu- bladder. While pronghorns and antelope have aptations include hollow hair fibers and a tion to North American species diversity. Re- a gallbladder, deer do not. light bone structure which allows maximum alizing the distinctiveness of this animal may Apart from the digestive adaptations, speed while running. ensure its conservation for years to come. pronghorns are built for speed. Pronghorns The social herding behavior of pronghorns Maybe it’s time to start thinking about chang- can run exceptionally fast, and they are built is similar to many deer and antelope spe- ing its name. Speed goat is my favorite… for maximal predator evasion through run- cies; however, there are some fundamental

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