Newborn northern fur seals (Callorhinus ursinus)--do they suffer from cold?
Several hundred thousand northern fur seals (C. ursinus) are born each summer during July at St. Paul Island in the Bering Sea. The weather in the area is usually cold, wet, and windy during the breeding season. At birth the pups are small (5--6 kg) and insulated only by a partly wettable pelt and a 2- to 4-mm layer of blubber. In air, the pups' lower critical temperature appears to be below the 6 degrees C 50-yr record low July temperature for the islands. During rainy weather much of the insulative value of the pelt is lost, and the pups, which already have a high resting metabolic rate of 3.5 W.kg-1, must increase heat production by shivering and/or nonshivering thermogenesis to maintain deep body temperature. The high level of metabolism (up to 18 W.kg-1) is supported by a very rich milk. The pups will, nevertheless, become hypothermic if their insulation is not improved through peripheral vasoconstriction and shedding of water from the pelt by periodic shudder. Even with these protections the newborn and very young pups are brought close to their limit of tolerance during rainy and windy days. Unfit pups are likely to succumb under such circumstances.
D000273:Adipose Tissue / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001833:Body Temperature Regulation; D010872:Caniformia / Q000502:physiology*; D003080:Cold Temperature; D046069:Fur Seals / Q000502:physiology*; D006197:Hair; D011891:Rain; D014919:Wind