Ovis dalli (Nelson, 1884)
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publication ID |
https://doi.org/ 10.5281/zenodo.6512484 |
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DOI |
https://doi.org/10.5281/zenodo.6581183 |
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persistent identifier |
https://treatment.plazi.org/id/03F50713-9937-FF8C-0374-FA6CF6C8F59E |
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treatment provided by |
Conny |
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scientific name |
Ovis dalli |
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207. View On
Dall’s Sheep
French: Mouflon de Dall / German: Dall-Schaf / Spanish: Carnero de Dall
Other common names: Alaskan White Sheep (dall), Stone's Sheep (stone)
Taxonomy. Ovis montana dalli Nelson, 1884 View in CoL ,
Yukon, Alaska.
Microsatellite data provide some support for recognizing two subspecies.
Subspecies and Distribution.
O.d. stonei]A. Allen, 1897 — Canada (Yukon Territory, N British Columbia). View Figure
Descriptive notes. Hentbods 130-178 cm (males) and 132-162 cm (females), tail, 8-13 cm (males) and 8-10 cm (females), shoulder height 91:6-109 cm (males) and 78.7-88. 9 cm (females), hindfoot 38-46 cm (males) and 28-41 cm (females); weight, males average 81-7 kg (up to 136 kg) and females 56-8 kg. Dall’s Sheep are either entirely off-white, occasionally with a black tail (dalli), or highly variable (stonei), from pale brown to grayish or blackish-brown in body color, with white underparts, white face, grizzled neck, and distinct rump patch or with darker hairs on cheeks, throat, and neck. In the palest individuals, dark hairs are restricted to a saddle-patch down each side and the outer sides of the foreand hindlegs. The subspecies intergrade and color variations occur within the same population. Diploid chromosome number is 54.
Habitat. Dall’s Sheep habitats consist of steep, rugged terrain adjacent to alpine, subalpine, and at lower elevations even forested areas that in winter have light snowfall and wind-blown sites cleared of snow that allow access to forage. Cold winter temperatures well below 0°C and windy conditions prevail. Gray Wolves (Canis lupus) and Coyotes (C. latrans) are the principal predators, but predation is not normally a major mortality factor.
Food and Feeding. They are principally grazers; in one study, annual diets consisted of 81-5% grasses and sedges. In other studies, winter diets consisted of 87-6% graminoids, 3% forbs, and 8:5% shrubs and summer diets consisted of 57% graminoids. Willows can be an important component of winter diets. Mineral licks are intensively used in some areas.
Breeding. The mating season is from mid-November to mid-December. Larger, dominant rams guard single, estrous ewes from subdominant and younger rams, who attempt to separate the ewe from the guarding ram. Most of the mating is done by dominant rams. Ewes are in estrus one to three days and will recycle if they do not conceive during the first estrous cycle. In healthy populations, ewes first mate as yearlings and give birth at two years of age; all older ewes can be pregnant. In some populations, reproduction can be delayed until ewes are older. Ewes 13-16 years old can continue to lamb. Prior to lambing, ewes leave herds and give birth in isolation. Shrubs may provide newborn lambs with concealment cover and shelter from the wind. Ewes join ewe-lamb groups after one or two days. Ewes give birth to one lamb, which weighs 3-2—4-1 kg, in May to mid-June, after a gestation period of 170-180 days. Twins are rare. Ewes join ewe-lamb groups one or two days after parturition but remain separated from barren ewe and yearling herds for several weeks. Lamb mortality during the first two weeks is approximately 28%, but lamb—ewe ratios vary from 8:100 to 81:100 with an average of 37:100.
Activity patterns. Dall’s Sheep are most active during daylight hours. During the shortened winter days in northern latitudes, they forage for only five hours daily when daylight is shortest but for progressively longer periods as daylight hours lengthen. Lactating females forage for longer periods than rams; adult rams foraged 9-1 hours daily, whereas lactating ewes foraged 11-9 hours and non-lactating ewes foraged 10-9 hours daily. The most active feeding period is usually at dusk. Nights are spent close to escape terrain. In the Arctic, where the sun does not rise in mid-winter, sheep feed in darkness.
Movements, Home range and Social organization. Winter ranges are smaller in area than summer ranges. Although in some regions ewes and rams use the same winter range, they segregate into separate ewe herds and ram herds. They exhibit a high degree of fidelity to seasonal ranges. Long-distance movements between winter and summer ranges can occur, some of which can involve movements through forested areas. In most instances, movements are between lower elevations to feed on spring vegetation and higher slopes later in the season to feed on the emerging vegetation following the receding snow line. Rams can also move to lower-elevation mountains to feed in brush-covered areas. Occasionally, small groups, especially young rams, move to areas as much as 40-50 km from the nearest known population; these movements are important in establishing new home ranges or reoccupying formerly used areas. Ewes associate with each other in ewe-lamb groups or ewe-lamb-yearling groups. Yearlings often begin to associate with ram groups during the lambing period and can join ram groups during the summer. Within ram groups, social interactions center on establishing and maintaining dominance rank.
Status and Conservation. Classified as Least Concern on The [UCN Red List. Most populations occur in undisturbed habitats. There are over 100,000 Dall’s (dall) and 14,500 Stone’s (stoner) Sheep. Die-offs from disease outbreaks have not been recorded, probably because of their isolation from domestic sheep. Mineral, oil, and gas exploration and extraction could have detrimental effects on habitats and populations over widespread areas in the future. Tourist disturbance, including vehicular traffic, has the potential to impede movements and cause sheep to move away from preferred foragingsites.
Bibliography. Bowyer & Leslie (1992), Bowyer et al. (2000), Bunch, Hoffmann & Nadler (1999), Bunnell (1982), Cowan (1940), Geist (1971, 1999), Groves & Grubb (2011), Grubb (2005), Hall (1981), Hoefs & Cowan (1980), Krausman & Bowyer (2003), Nichols (1978a, 1978b), Nichols & Bunnell (1999), Phillips et al. (2010), Rachlow & Bowyer (1998), Shackleton et al. (1997), Sheldon (1911), Worley et al. (2004).
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