Antilocapra americana, Ord, 1815

Don E. Wilson & Russell A. Mittermeier, 2011, Antilocapridae, Handbook of the Mammals of the World – Volume 2 Hoofed Mammals, Barcelona: Lynx Edicions, pp. 780-787 : 787

Pronghorn

Antilocapra americana

French: Pronghorn / German: Gabelbock / Spanish: Berrendo

Other common names: Prongbuck, Antelope; Sonoran Pronghorn (sonoriensis)

Taxonomy. Antilope americanus Ord, 1815 ,

plains and highlands of the Missouri River, USA.

Three subspecies recognized.

Subspecies and Distribution.

A.a.americanaOrd,1815—fromSCanada(SAlberta&SSaskatchewan)toN&CMexico.

A.a.peninsularisNelson,1912—Mexico(NBajaCalifornia).

A. a. sononensis Goldman, 1945 — USA (S

Arizona) and Mexico (N Sonora).

It was introduced on Lanai Island (Hawaii) in 1959; however, it never became well established there and seems headed for extinction.

Descriptive notes. Head-body 130-140 cm, tail 9.7-10. 5 cm, shoulder height 8687-5 cm, length of pinna 14-2 cm; weight 30-80 kg. Sexual size dimorphism approximately 10%. Reddish-brown dorsally, white ventrally, complex brown, black, and white patterning on face. Two horizontal white bars on ventral neck. White rump patch with erectile hairs. Long tapering muzzle with relatively narrow dental arcade. Cheek teeth hypsodont and selenodont. Large eyes set high and far back in the skull. Long slender limbs with no trace of lateral digits on the metapodials. Females have four mammae.

Habitat. Grassland and deserts of North America from near sea level to 3350 m. Prefer habitat with high forb content and diversity. Avoid closed habitats with limited lines of sight.

Food and Feeding. Highly selective browsers that consume principally forbs. Small amounts of grass are consumed in early spring. In autumn and winter, individuals shift more to browsing on shrubs.

Breeding. Females typically enter estrus for the first time in their second year, at about 16 months of age. Rarely, females have the first estrus at four months of age. Each female enters estrus each year until death, and bears large twin fawns the following spring. Fawns are weaned in late August and estrus occurs in midto late September. Males have mature sperm in the testes at four months of age, but usually do not compete successfully for matings until the third year. There is substantial skew in male mating success; this skew is created primarily by female choice. Each female makes an independent evaluation of males each year. Females tend to converge in their choices on a small population subset of males. These males, which sire about 60% of all fawns each year, have superior breeding value for offspring performance.

Activity patterns. Pronghorns maintain cycles of foraging and reclining/ruminating throughout each 24hour period. Individuals rarely appear to sleep. For females, time reclined varies from 25% to 35%, the minimum occurring during rut and the maximum occurring in spring. For males, time reclined varies from 15% to 35%, with the same seasonal minima and maxima. Both sexes devote the most time (56%) to forag-Ing in winter.

Movements, Home range and Social organization. Pronghorns are almost always found in groups. Group size and composition vary seasonally. The small spring and summer groups are composed either of females and fawns or of oneto three-year-old males. The large winter groups contain approximately equal numbers of each sex. Individuals are usually site-faithful to a circumscribed summer range. Migration to warmer, more snow-free winter range occurs in many populations, but in some of them not all individuals migrate. When undisturbed and not migrating, Pronghorns move about 6 km per day in the course of foraging movements and movements to shift from one group to another. Social groups are temporary aggregations of individuals. There are no social bonds that define groups or create group substructure.

Status and Conservation. The population of Mexico CITES Appendix I, the rest not listed. Classified as Least Concern on The IUCN Red List. There are approximately one million Pronghorns in North America, however, numbers do fluctuate depending on the severity of droughts and winters. About one-half of these occur in Wyoming. Many local populations are small and isolated. The degree of inbreeding depression is currently unknown, but is under study. Sonoran Pronghorn sonoriensis was listed as federally endangered by the USA in 1970, and numbers in the USA have been as low as 21. Nowadays,it is estimated that there are fewer than 300 individuals of the Sonoran Pronghorn in the USA and 200-500 individuals in Mexico. Race peninsularis was on The IUCN Red List at one time. Approximately 200 individualslive in and near breeding enclosures in Baja California.

Bibliography. Barbour & Schultz (1934), Barrett & Miller (1984), Bayless (1969), Beale & Smith (1970), Beintema et al. (2003), Birney & Baird (1985), Blair (1982), Boccadori et al. (2008), Bright & Hervert (2005), Bruns (1977), Bullock (1982), Byers (1997), Byers & Byers (1983), Byers & Hogg (1995), Byers & Moodie (1990), Byers & Waits (2006), Byers, Byers & Dunn (2006), Byers, Moodie & Hall (1994), Byers, Wiseman et al. (2005), Cancino, Ortega-Rubio & Rodriguez (1998), Cancino, Ortega-Rubio & Sanchez-Pacheco (1996), Carlton & Mckean (1977), Clemente et al. (1995), Colbert & Chaffee (1939), Cook & Irwin (1985), Cook et al. (1949), Courtney (1989), Deblinger & Alldredge (1991), Dhindsa et al. (1974), Dirschl (1963), Easterla (1965), Fichter (1987), Fox etal. (2000), Frick (1937), Gilbert (1973), Goldsmith (1990), Hesse (1935), Hildebrand & Hurley (1985), Hoffman et al. (2008), Hoskinson & Tester (1980), Jorge & Ortega-Rubio (1994), Kessler et al. (1981), Kraus & Miyamoto (1991), Krausman et al. (2005), Krueger (1986), Lee et al. (1994), Lindstedt et al. (1991), Maher (1991, 1997), Martin & Parker (1997), Mckean & Walker (1974), Mitchell (1967), Mitchell & Smoliak, (1971), Moodie & Byers (1989), Moy (1970, 1971), O'Gara (1969, 1978), O'Gara et al. (1971), Paradiso & Nowak (1971), Quinn (1930), Reynolds (1984), Reynolds & Laundre (1990), Ryder & Irwin (1987), Schwartz & Nagy (1976), Schwartz et al. (1977), Smith & Shandruk (1979), Solounias (1988), Waring (1969), Webb (1973), White et al. (2007), Wild et al. (1994), Wiseman et al. (2006).

Figures

Pronghorn

Subspecies and Distribution. A.a.americanaOrd,1815—fromSCanada(SAlberta&SSaskatchewan)toN&CMexico. A.a.peninsularisNelson,1912—Mexico(NBajaCalifornia). A. a. sononensis Goldman, 1945 — USA (S Arizona) and Mexico (N Sonora). It was introduced on Lanai Island (Hawaii) in 1959; however, it never became well established there and seems headed for extinction.