Pronghorn - Antilocapra americana
Pronghorn In Bunchgrass - Pronghorn, also know as Antelope, standing in Bunchgrass. Antilocapra americana
Global Rank:
G5
State Rank:
S5
Agency Status
USFWS:
none
USFS:
none
BLM:
none
CFWCS Tier:
3
General Description
Coat rich russet-tan with white underside; large white rump patch; two white bands across throat; black markings on head; eyes large, dark; dew claws absent; horns of adult bucks 13-16 inches long with prongs and curved tips; horn sheaths shed annually; about 70% of adult does have horns (averaging 1 1/2 inches long); adult bucks weigh 125 lbs., does 110 lbs. Adult bucks territorial from march through September; does and fawns in small herds drift on and off buck's territories in spring and summer; herds of bachelor bucks excluded from territories; all ages and both sexes congregate in winter herds; during severe winters, herds drift for long distances seeking food; barriers to such movements limit populations; excited animals emit explosive snorts, erect white rump patches, and emit musky odor from glands in rump patches (FWP). Upperparts are reddish brown to tan; underparts, lower sides, rump, and two bands on the neck are white; neck has a short black mane; male has a black band along each side of the snout, a black patch on each cheek, and sometimes black bands on the neck; males and most females have horns (larger and usually forked in males; sheaths are shed annually); two toes on each hoofed foot; head and body length 100-150 cm, tail 8-18 cm, mass 36-70 kg (Nowak 1991).
Diagnostic Characteristics
Shape of the horns and annual shedding of horn sheaths are unique among north american ungulates. differs from the bighorn sheep in having white bands on the neck and slightly curved horns rather than strongly curved horns. differs from deer in having white lower sides rather than lower sides the same basic color as the upper sides; also, deer lack conspicuous white bands on the neck.
Distribution
Montana Range
Migration
May migrate in response to severe weather or habitat condi- tions. Migration stops when conditions moderate.
Habitat
Open, rolling sagebrush/grasslands (FWP). Winter habitats less diverse than sum. Sagebrush-grassland preferred (Bayless 1967). Summers: mixed shrub, perennial grass- lands, silversage & annual forb types (Armstrup 1978). Also crop- lands (Wentland 1968). Pref. corroborate w/ seasonal food habits.
Food Habits
Forbs in spring and summer; browse, especially sagebrush, in winter; small amounts of young grasses in spring and after fall rains (FWP). Presence of browse, particularly big sagebrush, is important limiting factor on N ranges. Forbs im- portant in summer, grasses usually minor all year (Wentland 1968, Bayless 1967).
Ecology
Populations extremely dynamic. Move S during severe win. weather. Fences can be a major obstacle.May be incompatible w/ sheep, compat. w/ cattle. Extensive cultivation over-simplifies, reduces habitat .
Reproductive Characteristics
Breed in late September; two grayish-brown fawns; bucks fight viciously and sometimes fatally; territorial bucks hold harems to breed; bucks shed horn sheaths in November; females usually breed when 1 1/'2 years old, but may breed as fawns (FWP). Females 1st breed as yearlings. Prod. young at 2 yrs. occas. breed as fawns. Males 1st breed as yearlings. Freq. about 1.9-1.95 viable conceptus/doe. Parturition mid-late May.
Citations & Sources