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Species
Rangifer tarandus (Linnaeus, 1758)
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Caribou, and their domestic counterparts - reindeer, have been very important in the cultures of native peoples througout the arctic. Several Siberian, Scandinavian, and American native cultures are built around herding caribou.
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Rights holder/Author | ©1995-2012, The Regents of the University of Michigan and its licensors |
Source | http://www.biokids.umich.edu/critters/Rangifer_tarandus/ |
Caribou, or Reindeer, is the only deer species in which both males and females have candelabra-like antlers. They live in large, migratory herds along the tree line of northern forests, eating mostly grass-like plants and shrubs in summer, and lichen, which carpets the snow-covered forests, in the winter. Getting at winter feed by digging through the snow can lead to intense competition, which may explain why females also carry antlers. During the breeding season, males compete with one another for access to females, using their antlers in jousting matches. They become completely devoted to the rituals of mating, failing even to eat, and losing their built up energy reserves in the process. Females give birth at traditional calving grounds on the open tundra during the spring, after a gestation of seven months. Then they pour all of their energy reserves into nursing their calves for a month. There are more than 2,000,000 Caribou in North America, but they are less successful in the southern parts of their range where they must cope with humans and other predators.
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Mammal Species of the World
More images, video and sound of the Peary caribou, a subspecies
Chile Central
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Rights holder/Author | Pablo Gutierrez, IABIN |
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Caribou are mainly grazing herbivores. Their diet varies depending on the season. In summer they eat the leaves of willows and birches, mushrooms, cotton grass, sedges, and other ground dwelling kinds of vegetation. In the winter lichens are an important food source, although they continue to eat whatever vegetation is available.
Plant Foods: leaves; roots and tubers; wood, bark, or stems; bryophytes; lichens
Other Foods: fungus
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Rights holder/Author | ©1995-2012, The Regents of the University of Michigan and its licensors |
Source | http://www.biokids.umich.edu/critters/Rangifer_tarandus/ |
Breeds mostly in October. Gestation lasts about 227-230 days. Cows bear usually 1, sometimes 2, young in May and June (early June in northern British Columbia). Calves precocious. Adult females sometimes skip reproduction for a year, in response to nutritional stress (Cameron, 1994, J. Mamm. 75:10-13). In northeastern Alaska and adjacent Canada, 80% of adult females (age 3 years or older) gave birth each year (Fancy et al. 1994).
Global Short Term Trend: Decline of 50-70%
Comments: Vors and Boyce (2009) gathered population data for 58 major caribou and reindeer herds throughout the global range and found that 34 were reported as declining, eight were increasing, and 16 had no data. The authors gathered 40 time series of population estimates for smaller herds within the major herd ranges. The time series spanned an average of 21.6 years and population estimates were available for an average of 9.9 years. Of these herds, 11 were in decline for fewer than 10 years, eight were in decline for 10-19 years, and six were in decline for more than 20 years. Mean percentage decline from known population maxima for these herds was 57 percent.
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The various subspecies of caribou display a wide range of size. Generally speaking, the subspecies inhabiting the more southerly latitudes are larger than their northern cousins. Caribou can have shoulder heights of up to 120 cm and total length ranges from 150 to 230 cm. They have short tails. There is marked sexual dimorphism, with males of some subspecies being twice as large as females. The coat of the caribou is an excellent, lightweight insulation against the extreme cold temperatures they face. The hairs are hollow and taper sharply which helps trap heat close to the body and also makes them more buoyant. Color varies by subspecies, region, sex, and season from the very dark browns of woodland caribou bulls in summer to nearly white in Greenland (R. t. groenlandicus) and high Arctic caribou. White areas are often present on the belly, neck, and above the hooves. The hooves are large and concave, which support them in snow and soft tundra, conditions that they often face. The broad hooves are also useful when swimming. Caribou make an audible clicking noise while walking, which is produced from tendons rubbing across a bone in the foot. Rangifer tarandus is the only species of deer in which both sexes have antlers. Mature bulls can carry enormous and complex antlers, whereas cows and young animals generally have smaller and simpler ones. Mature bulls usually shed their antlers shortly after the rut whereas cows can keep theirs until spring.
Range mass: 55 to 318 kg.
Range length: 150 to 230 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger; ornamentation
Average basal metabolic rate: 119.66 W.
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Rights holder/Author | ©1995-2013, The Regents of the University of Michigan and its licensors |
Source | http://animaldiversity.ummz.umich.edu/accounts/Rangifer_tarandus/ |
More info for the terms: bog, cover, lichen, lichens, selection, shrubs, tree, wildfire
Food availability influences food selection. Caribou prefer vascular plants and mushrooms but exploit other food sources when these are not available [12]. The vascular plant species most commonly eaten by caribou throughout the United States and Canada include the young buds, catkins, leaves, and/or sprouts of water sedge, water horsetail (E. fluviatile), mountain cranberry, velvetleaf blueberry, bog blueberry, arctic willow (S. arctica), sheathed cottonsedge (Eriophorum vaginatum), bog Labrador tea, northern Labrador tea (Ledum decumbens), bog birch, and leatherleaf (Chamaedaphne calyculata) [2,14,26,66,79,80,96,98,99,103,109]. Other locally important foods include arctic dryad, saxifrage (Saxifraga spp.), bog rosemary (Andromeda spp.), black crowberry (Empetrum nigrum), sheep-laurel (Kalmia angustifolia), bog-laurel (K. polifolia), spruce, jack pine, tamarack, sedges (Cyperaceae), blueberries (Vaccinium spp.), willows (Salix spp.), birches (Betula spp.), grasses, and mosses [12,14,27,66,80,96,98,103,109]. Fungi, especially Boletus spp., Coprinus spp., Lycoperdon spp., and Morchella spp., are readily eaten in late summer and fall [12,80,103]. After fall frost, caribou consume terrestrial lichens and evergreen leaves [12]. In addition to milk, calves as young as 2 weeks old ingest leaves of willows, bog Labrador tea, leaves and stems of sedges and black crowberry, and fruticose lichens, including cup lichens (Cladonia spp.) [103]. For more complete lists of caribou diets, see Bergerud [12,14], Cringan [27], Miller [80], and Skoog [103] .
Lichens are prominent in the caribou diet throughout the year, but reach greatest importance in winter [27,80,96,101]. Lichens commonly eaten are reindeer lichen, star reindeer lichen, spineless reindeer lichen, tree reindeer lichen (Cladonia arbuscula), other reindeer lichens (Cladonia spp.), cup lichens (C. amaurocraea and C. uncialis), cetraria lichen (Flavocetraria nivalis), Iceland-moss (Cetraria islandica), felt lichen (Peltigera canina), and snow lichens (Stereocaulon spp.) [2,12,14,26,80,99,101,108]. Other lichens, including witch's hair lichens (Alectoria jubata, A. sarmentosa, and A. ochroleuca) and brittle lichens (Cornicularia spp.) are locally important food sources when available [2,26]. In British Columbia, horsehair lichens (Bryoria spp.), which are highly valued as forage in the area, are more abundant on subalpine fir and Engelmann spruce than on whitebark pine (Pinus albicaulis), lodgepole pine, or alpine larch (Larix lyallii) [60].
Lichens are the primary foods of caribou in winter [27,80,96,101]. However, lichens are generally low in nutrients, and caribou often lose weight with a winter diet heavy in lichens [12,33,80]. Caribou may persist on a diet that limits or excludes lichens, since caribou are able to exploit vascular plant resources when available [14,33]. In winter, snow accumulation influences caribou diet [12,92]. By mid-April in Saskatchewan, snow hardening made it difficult for the caribou to forage beneath the snow, so arboreal lichens were the primary available food source followed by terrestrial lichens, bog Labrador tea, and other deciduous shrubs and trees [79,80]. When caribou population densities were high on the Slate Islands in Lake Superior, caribou lightly browsed mountain maple (Acer spicatum), American mountain-ash (Sorbus americana), willows, red-osier dogwood (Cornus sericea), and downy arrowwood (Viburnum rafinesquianum) in winter [27]. Woodland caribou in British Columbia forage on arboreal lichens, subalpine fir, Engelmann spruce, and western hemlock in early winter when show accumulation is rapid. Oregon boxwood (Paxistima myrsinites) and other vascular plants were eaten in early winter when snow accumulation was slow [92]. When the snow forms a hard crust in open habitats, caribou move to forests to feed on arboreal lichens [12]. During periods when snow cover was ≤20 inches (51 cm) deep, woodland caribou in British Columbia fed on grouse whortleberry (Vaccinium scoparium), cup lichens, and horsehair lichens. When snow was ≥24 inches (62 cm) deep, they almost exclusively ate horsehair lichens and possibly small amounts of witch's hair lichen [60]. Overgrazing by caribou has reduced the amount of available forage and habitat on Alaskan islands, while wildfire has reduced lichen availability on the Alaskan mainland [106].
During northward migration in Saskatchewan in mid-February, barren ground caribou fed in early morning and early evening [80]. Caribou tend to move almost continuously, even when foraging, which reduces the possibility of overgrazing a feeding area [103]. Snow softens by late winter or early spring, making it possible for the caribou to feed on terrestrial lichens and ericaceous plants under the melting snow [80]. Caribou dig craters in the snow to forage for lichens and other vegetation [12,17]. Caribou prefer to crater in soft, shallow snow [96]. Only one caribou feeds in a crater at a time, and they compete for the most preferred craters [80].
Males compete for access to females during the fall breeding season, or rut. This occurs in October and early November. During this time males may engage in battles that leave them injured and exhausted. Dominant males restrict access to small groups of 5 to 15 females. Males stop feeding during this time and may lose weight rapidly.
Mating System: polygynous
In late August and September, prime bulls shed the velvet that surrounds their antlers. Fighting among males (sparring) begins shortly after that, with the rut (breeding season) usually occurring in October. Females can breed as early as 16 months of age but usually begin to breed at 28 months. With good nutrition females give birth to calves each year, but may skip years in areas with low quality forage. A single calf, weighing 3 to 12 kg, is born after about 228 days, in May or June. Twins have been reported, but are rare. Calves are weaned during the first week of July, but also begin to graze on grasses soon after birth. Calves rely mainly on grazing for nutrition after 45 days old.
Breeding interval: Caribou breed once yearly.
Breeding season: Breeding typically occurs in October.
Range number of offspring: 2 (high) .
Average number of offspring: 1.
Average gestation period: 7.6 months.
Average weaning age: 1.5 months.
Range age at sexual or reproductive maturity (female): 16 (low) months.
Average age at sexual or reproductive maturity (female): 28 months.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous
Average birth mass: 6500 g.
Average gestation period: 228 days.
Average number of offspring: 1.
Average age at sexual or reproductive maturity (male)
Sex: male: 680 days.
Newborn calves are precocial, being able to suckle minutes after birth, follow their mother after an hour and are capable of outrunning a human at one day of age. Calves nurse exclusively for their first month, after which they begin to graze. They will continue to nurse occasionally through early fall, when they become independent.
Parental Investment: no parental involvement; precocial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)
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Rights holder/Author | ©1995-2012, The Regents of the University of Michigan and its licensors |
Source | http://www.biokids.umich.edu/critters/Rangifer_tarandus/ |
Major Threats
Poaching is a major threat in the Russian Federation (A. Tikhonov pers. comm. 2006). The causes of decline of the Novaya Zemlya subspecies pearsoni are not known (A. Tikhonov pers. comm. 2006). Loss of habitat in Finland (through logging) may pose problems, and there is increased disturbance to the species in some areas due to winter sporting activities. Hybridisation with semi domesticated reindeer is a potential problem for some subspecies and subpopulations (H. Henttonen pers. comm. 2006, Ruusila and Kojola in press).
White-tailed deer carry and disperse into the environment meningeal worms that usually are fatal to moose and caribou but are clinically benign in deer; hence, white-tailed deer, through worm-mediated impacts, commonly are believed to exclude moose and caribou from areas where deer occur (see Schmitz and Nudds 1994). Predation by an expanding coyote population threatened a remnant caribou herd in southeastern Quebec (Crete and Desrosiers 1995). Long-term steady decline in the taiga-dwelling population in Ontario has been associated with the expansion of forest harvesting (Schaefer 2003).
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Rights holder/Author | © International Union for Conservation of Nature and Natural Resources |
Source | http://www.iucnredlist.org/apps/redlist/details/29742 |