Odocoileus hemionus (Rafinesque, 1817)

Don E. Wilson & Russell A. Mittermeier, 2011, Cervidae, Handbook of the Mammals of the World – Volume 2 Hoofed Mammals, Barcelona: Lynx Edicions, pp. 350-443 : 436

37.

Mule Deer

Odocoileus hemionus

French: Cerf mulet / German: Maultierhirsch / Spanish: Ciervo mulo

Other common names: Black-tailed Deer (columbianus and sitkensis)

Taxonomy. Cervus hemionus Rafinesque, 1817 ,

Big Sioux River, South Dakota ( USA).

A study on mtDNA has confirmed that there are two distinct groups, a northern coastal one (“Black-tailed Deer”) and an eastern and south-western one (true Mule Deer). The large divergence between these two lineages seems to provide evidence for separate ice-free refugia during the last glacial maximum, about 18,000 years ago. Mule Deer persisted south of the ice sheet in multiple refugial populations. Black-tailed Deer probably survived in a single refugium in the Pacific Northwest, with a slow post-glacial recolonization, resulting in a loss of genetic diversity. Here eight subspecies are recognized.

Subspecies and Distribution.

O.h.hemionusRafinesque,1817—RockyMtsfromYukontoTexasandNewMexico.

O.h.californicusCaton,1876—CCalifornia.

O.h.cerrosensisMerriam,1898—NWMexico(CedrosI,BajaCalifornia).

O.h.columbianusRichardson,1829—coastalregionfromPortSimpsoninBritishColumbia(WCanada)toCCalifornia(WUSA).

O.h.eremicusMearns,1897—SWUSA(Arizona,NMexico).

O.h.fulbiginatusCowan,1933—SWUSA(SCalifornia)andNWMexico(NBajaCalifornia).

O.h.peninsulaeLydekker,1898—NWMexico(SBajaCalifornia).

O. h. sitkensis Merriam, 1898 — coastal S Alaska.

Descriptive notes. Head-body 150-180 cm for males (adult bucks) and 135-155 cm for females (does), tail 15-23 cm, shoulder height 85-105 cm (bucks) and 75-95 cm (does); weight 50-110 kg (adult bucks) and 35-65 kg (adult does). The heaviest animals occur in the northern Rocky Mountains, with records of 210-230 kg for exceptional bucks. Adult bucks average 50-70% heavier than does. Generally a mediumsized deer similar to the White-tailed Deer ( O. virginianus ), but with a relatively shorter and narrower tail that is white to black above, or tipped with black. The ears are very large, around two thirds the length of the face. Males have antlers, with a main beam that grows upward and then bifurcates in equal-length forked tines (“dichotomous branching”); the subbasal snag is short. The lacrimal fossa is deep. The coat is reddishbrown in summer, grayish-yellow, gray, or dark brown in winter. The rostrum is pale and the forehead has a dark patch. Molts in May and September. Newborn fawns are spotted. Nasal, preorbital, metatarsal, tarsal, and front and rear interdigital and caudal glands are generally present. The metatarsal gland is large. There are two main phenotypes, the Black-tailed Deer of the north-west coast, which has a tail thatis black above and a moderately large metatarsal gland, and the true Mule Deer of the south-west coast and inland, which has a conspicuous white rump patch, a white tail with a black tip, and a very large metatarsal gland. Permanent dentition of 32 teeth. Molars erupt at 6-18 months of age. Males sprout antler pedicles at three months of age. The first antler set, small buttons, develops at 8-9 months of age. The second set, in yearling bucks, generally consists of spikes. Adult antlers are usually 45-65 cm in length but can be longer, up to 75 cm. Antler casting occurs from to late January to March. Regrowth begins in April-May, from two weeks to two months after antler casting. Velvet shedding occurs in September.

Habitat. It is an ecotone deer, preferring open forest and scrubland associated with steep and broken terrain. It also lives in coastal coniferous rain forests and on prairies and in semi-desert shrub habitats. Snow depth of 30 cm may impede movements, and depth more than 50 cm prevents the use of an area.

Food and Feeding. It is an opportunistic intermediate feeder, with a tendency to be selective on various types of browse.

Breeding. Puberty is generally reached by females at about 18 months of age, rarely at 6-7 months. Males attain physiological sexual maturity at 18 months, but their opportunities to mate are low up to 2-3 years of age. Rutting season peaks between November and January. Dominant bucks court and mate estrous does. The courtship is initiated by a low-stretch approach of the buck, followed by a slow pursuit in small circles. Females are seasonally polyestrous, with an estrous cycle of 23-28 days and a receptive period of 24-36 hours. Mean pregnancy length is 203 days, with a birth peak between June and July. Primiparous does give birth to a single fawn; adults tend to produce twins. The spotted newborns weighs 2.7-4 kg and remain hidden for the first week. At three months of age they lose the spots, and at three or four months are weaned. Full weight is attained at 2-3 years of age by females, at 7-8 years by males. Maximum longevity is 19-20 years, but very few animals survive beyond 8-10 years. Main predators are Pumas (Puma concolor), Coyotes (Canis latrans), and Bobcats (Lynx rufus).

Activity patterns. Mule Deer are mainly active at dusk and dawn.

Movements, Home range and Social organization. It is a saltatorial runner with a specialized flight gait, the fourfooted bound known as “stotting.” For short durations it can reach 40 km /h. Generally home ranges are relatively small, 2-5-5 km?, larger in males. In northern latitudes and in montane areas, decreasing temperatures and snow fall prompt 15-30 km seasonal movements from higher to lower elevations. It is a moderately social deer. Females form matrilinear groups. Males are solitary orlive in small bands of unrelated individuals. Large temporary feeding aggregations in open ground are common in winter and early spring.

Status and Conservation. Classified as Least Concern on The [UCNRed List. Persecution and habitat destruction were responsible for the dramatic decline in the 19" century. Predator control, law enforcement, and habitat diversification caused by human activities (logging, burning, livestock ranching) all improved the living conditions for Mule Deer, which increased in abundance and distribution to a peak population of 7-5 million in late 1950s. From 1980 on, the total population has seemed substantially stable at about five million animals. Annual harvest in late 1990s was 535,000 individuals.

Bibliography. Anderson et al. (1974), Anderson & Wallmo (1984), Crete & Daigle (1999), Geist (1998), Kie & Czech (2000), Mackie et al. (2003), Martinez-Munoz et al. (2003), Wallmo (1981).

Figures

36. White-tailed Deer (Odocoileus virginianus), 37. Mule Deer (Odocoileus hemionus), 38. Marsh Deer (Blastocerus dichotomus), 39. Pampas Deer (Ozotoceros bezoarticus), 41. South Andean Huemul (Hippocamelus bisulcus), 42. Northern Pudu (Pudu mephistophiles), 43. Southern Pudu (Pudu puda)

Subspecies and Distribution. O.h.hemionusRafinesque,1817—RockyMtsfromYukontoTexasandNewMexico. O.h.californicusCaton,1876—CCalifornia. O.h.cerrosensisMerriam,1898—NWMexico(CedrosI,BajaCalifornia). O.h.columbianusRichardson,1829—coastalregionfromPortSimpsoninBritishColumbia(WCanada)toCCalifornia(WUSA). O.h.eremicusMearns,1897—SWUSA(Arizona,NMexico). O.h.fulbiginatusCowan,1933—SWUSA(SCalifornia)andNWMexico(NBajaCalifornia). O.h.peninsulaeLydekker,1898—NWMexico(SBajaCalifornia). O. h. sitkensis Merriam, 1898 — coastal S Alaska.