In winter, less time is spent feeding and more in resting.  It is at this time that the availability of food becomes crucial.  The accumulation of snow and wind-packing may severely restrict areas where vegetation can be reached.  Furthermore, wet snows or repeated thawing and freezing, result in a hard crust that prevents snow removal by wind and is difficult for the sheep to dig through.  Under these conditions, sheep must rely heavily on stored fat until spring.

Minerals from mineral licks are an essential component of the diet of Dall's sheep.  Well-established trails lead to the licks, which are used most frequently in the spring and early summer.  Ewes with lambs are the most frequent visitors, and they may linger for days in the vicinity of a lick.

Predators

Dall's sheep in the NWT have a number of predators including wolves, black bears and grizzly bears, wolverine, lynx, coyotes, and golden eagles. The amount of predation on Dall's sheep in the Northwest Territories is unknown. The rugged terrain preferred by sheep, and their usual proximity to precipitous escape areas affords them considerable protection from most predators.  Each year, however, some lambs and adults are taken by predators, especially by the more agile species, such as wolves.

Parasites

Dall’s sheep in the NWT are generally healthy, but they are hosts for a variety of parasites.

• Dall’s sheep are infected by a variety of gastro-intestinal parasites, none of which can be transmitted to humans, including the roundworms Marshallagia spp., Nematodirus spp., Trichuris schumakovitschi, Skrjabinema ovis, and the protozoa Eimeria. These parasites don’t appear to cause death in sheep, however, heavy infections with the abomasal worm Marshallagia spp. are associated with poorer body condition and lower pregnancy rates in ewes.
   

• Parelaphostrongylus odocoilei is a roundworm found in the muscles of almost 100% of Dall’s sheep in the Mackenzie Mountains, but not the Richardson Mountains. Eggs of P. odocoilei are deposited in the blood vessels and carried to the lungs. In the lungs they hatch to larvae and cause considerable inflammation.  Death due to respiratory failure has occurred in at least one heavily infected yearling. The role of this parasite in the health of the population is under investigation. It is not transmittable to humans. 
   

• Protostrongylus stilesi, or sheep lungworm, is present in almost 100% of Dall’s sheep in the Mackenzie and Richardson Mountains. Lungworm has been linked to pneumonia outbreaks and die-offs of bighorn sheep in the south, but other disease agents (bacteria and sometimes viruses) and a stress trigger are considered more important in causing this complex disease. Pneumonia cases have been sporadically reported in Dall’s sheep of the Mackenzie Mountains, but no die-offs have been detected and populations are stable.
   

• Contagious ecthyma can be found in Dall's sheep in the NWT, and can occasionally infect other ungulates including caribou and muskox. This virus causes scabby lesions most commonly found on the lips, mouth and skin of the face, around the edge of the hooves, and on the udder, vulva or pizzle. If mouth lesions are severe enough, animals will not feed, and lameness may occur due to foot lesions. In both cases, animals will lose condition and in sever cases may even die of starvation. The disease is self limiting, and animals will generally recover completely. The orf virus can infect people, so care should be taken in handling obviously infected animals.