North American Bovids arrived during Pleistocene via Bering land bridge. Because of the cold climate, those not adapted to cold could not make it. Thus we have fewer species.
Almost no free ranging populations left. Wood Bison NP in NW Terr. Canada, and Yellowstone National Park have populations free ranging and soewhat self regulated.
Bison are the largest terrestrial mammal in NA- bulls up to 2000 lbs. Taxonomy is unclear. Woods bison have some distinguishing physical characteristics, such as a more steeply contoured shoulder hump. However, the bison in Yellowstone, which are supposed to be plains bison, also exhibit this (perhaps an adaptation to deep snow? Bison as a group can survive in deeper snow than any other ungulate, and Yellowstone offers the harshest winters in that regard.)
Bison are social herd animals, the largest groups historically being the plains bison migration herds. Small groups/herds are generally dominated by mature bulls in a hierarchy of dominance. Bull do not gather harems, but become protective of 1 cow at a time. A small % of cows can breed as yearlings, most at 2, some not till 3. Usually bear 2 calves in a 3 year period. In National Parks culling is no longer practiced thus mortality is natural. The most significant cause in the absence of wolves is starvation due to limited forage (the carcasses provide significant food for grizzlys in spring). Bison are subject to wolf predation in winter in Wood Buffalo NP, Canada, and recently in Yellowstone. Diseases have also caused significant mortality- Anthrax, Tuberculosis and Brucellosis. The latter causes abortions, and can be transmitted to and from cattle. Bison are more resistant than cattle, and ranchers worry about bison as alternate host. Neither Wyoming or Montana encourage free ranging bison. Bison that wander out of Yellowstone into Montana are culled.
Bison are predominantly grazers. Grazing of large herds of bison was probably the predominant factor in maintaining the shortgrass plains (cattle have replaced the bison in that role). Prefer grasses and sedges, even in winter. Can subsist on lower quality forage than a domestic cow- similar mechanism as in Caribou- nitrogen recycling to maintain more active rumen bacteria and increase protein synthesis. During blizzards, BMR apparantly slows down- bison huddle together and just stand there, getting covered up with snow to keep warm. Big enough to break out of the drifts later.
Found at highest elevations in mountains- cliffs, ledges, talus slopes and alpine tundra. Found from S. Alaska through BC, Pac. NW and Rockies. They will winter as high as snow free areas exist. In severe winters will migrate down as do other ungulates. Mt. goats are "nip feeders"- selecting portions of grasses, sedges, forbs and browse, mosses and lichens.
Hunting is closely regulated. Biggest natural mortality factor is accidents- falling off cliffs or snow cornices. Predation by Mountain lion is a mortality factor where ranges overlap. Predation of new-born kids by golden eagles is significant in some areas for a short period.
Both sexes may be hunted (except nanny with kids). breed at 2.5 yrs, 25% twins. Horn glands: larger in males. mark bushes by rubbing (supra-orbital gland).
Mountain goats have been introduced into the Olympic National Park where they have caused vegetation damage.
Thinhorn, or Dall & Stone sheep found in Alaska to British Columbia. Bighorns found from BC to Mexico.
Rocky Mt. bighorns found in the Rockies from northern New Mexico to British Columbia.
The California bighorn is found in the Cascades of B.C and Pac. NW, mountains of Great Basin and Sierras okf California.
The desert Bighorn found in mountains of the desert SW from Arizona to New Mexico.
Both sexes are horned, but those of ram are massive, forming a full curl in older (5+yrs.) animals (in most states, a 3/4 curl is minimum for harvesting).
Ewes on a high nutritional plane may breed at 1.5 years, but more commonly at 2.5. One lamb is most common.
During most of the year, ewes and lambs form nursery bands while rams form ther own. They are together during rut when dominant rams do MOST of the breeding (but not all). Dominance is determined by fighting (Head ramming and pushing). Must be careful not to reduce ram/ewe ratio to below 25/100. Young rams learn about their home range and social role from older rams. Older rams protect ewes from constant harassment by young rams which would result in loss of condition & productivity. Younger rams hang out on periphery of rutting groups ("sattelites" or "coursers" ) and sneak in for a quick "connection" with a female.
Must maintain a healthy population of dominant rams for successful breeding and reproduction.
Predators such as wolves, mt. lions and eagles have been known to kill bighorns, however, predator control is not considered a necessary factor in Management throughout MOST of its range. In W. Texas however, predation by Mt. lions has been a major factor in failure of reintroductions.
CONTROL OF COMPETITIOM IS IMPORTANT. Bighorns prefer grasses and sedges, but will also consume forbs and browse. Competition may come from deer, elk or mainly domestic livestock. Livestock grazing must be closely controlled or prohibited on key bighorn ranges. (feral burrows a major competitor in SW with desert bighorn). Another MAJOR competitor is the introduced Audad sheep.
This species was introduced in E. NM and Texas. It is a serious competitor with deer, elk, bighorns and cattle. It breeds year-round, ewes may have 2 young per year, and productivity is phenomenal. Very large herds in W. Texas, but so far have been somewhat controlled in Bighorn ranges.
Bighorns are susceptible to lungworm, which causes pneumonia (life-cycle via snail). May be carried by domestic sheep, which must be excluded from bighorn ranges. Habitat varies from Alpine tundra-rocky peaks to sagebrush and pine foothills; desert mt. peaks to desert grassland. Migrates up in summer, down in winter.
FAMILY LEPORIDAE- rabbits (genus Sylvilagus)and hares(genus Lepus). Rabbits bear altricial young (relatively undeveloped- hairless), hares bear precocial young- more developed. Hares are larger than rabbits and have longer hind legs. Rabbits tend to burrow, hares do not.
Field guide lists 8 species of cottontail rabbit (Sylvilagus) in US, 2 in New England- the Eastern cottontail and the New England cottontail (rare, being replaced by Eastern). Cottontails breed in witner, spring and summer. May have 4-7 litters per year, 3-5 young per litter.
Field guide also lists 6 native species of hares or jack rabbits - The snowshoe hare N. US & Canada), Arctic (N. Canada) and tundra hares (Alaska). These may have 2-7 litters per year, 2-3 per litter.
3 jackrabbits- Whitetail, blacktail and antelope (western US and Mexico). These may have 3 litters per year, 3 per litter. Jackrabbits generally plains or desert inhabitants. Consume large amounts of grasses and forbs for their size, and large populations can pose competition with livestock for forage. Mostly nocturnal. Come out to feed along roads at night during droughts. I counted 500+ early one morning on a 25 mi stretch of road in W. Texas. Road kills provide lots of buzzard food. LONG EARS---COOLING