The Influence of Climate on Metabolic and Thermal Responses of Infant Caribou

Abstract

Metabolic and thermal responses of infant caribou to climate were measured during the June calving period on the barrens in the area of Mosquito Lake and Beverly Lake, N.W.T. It was found that temperature regulation was well established at birth and that the calves were very sensitive metabolically to cold, wind, and precipitation. The metabolic rate was doubled by a lowering of temperature to about 0 °C, but cold combined with wind and precipitation elevated the metabolic rate to over five times the resting value. Calves which were exposed without protection to such conditions eventually became hypothermic and died. Weather conditions during storms on the barrens are sufficiently severe to produce some mortality in animals exposed without protection. The possibilities for prediction of mortality from wind chill values and estimated fur heat loss are discussed.

Rain more important than windchill for insulation loss in Svalbard reindeer fur

“…Wet Svalbard reindeer calf fur appears more resistant to heat loss than other reindeer calf fur, and Svalbard reindeer are sedentary in behaviour (Tyler, 1987). Barren-ground caribou calves may move long distances in adverse weather (Hart et al, 1961), which results in metabolic costs for both movement and thermoregulation given the maximized surface area to volume ratio. In contrast, Svalbard reindeer calves remain on the calving sites, and whenever necessary may utilize the lying position, which reduces the surface area to volume ratio and hence exposure to wind, rain or temperature.…”

“…Hart et al (1961), studying infant caribou calves (Rangifer tarandus groenlandicus), observed that a combination of cold ambient temperatures, wind and wet fur increased the resting meta-7 Rain more important than windchill for insulation loss in Svalbard reindeer fur…”

Rangifer 1981 Vol. 1 (1): 1-56

“…However, of course, wetting of the pelt and wind may create a situation which is barely tolerated by infants (see e.g. Hart et al 1961). According to our data it is likely that shivering plays only a minor role in the heat production of a newly born calf.…”

“…The effects of air velocity, direction and wetness of the skin on heat loss were examined as well. Hart et al (1961) studied the metabolic and thermal responses of infant caribou. The metabolic rate was doubled by a lowering of temperature to 0°C, but cold combined with wind and precipitation was observed to elevate the metabolic rate to over 5 times the resting value at 20°C.…”

A comparison of temperature regulation in neonatal and adult hispid cotton rats, Sigmodon hispidus texianus, from southern Texas and northern Kansas

“…The degree of thermoregulatory ability in neonates is dependent upon such factors as body size, thermal insulation, degree of neuro logical control and thermogenic capability at birth (Hull, 1973)-Large neonates, such as newborn lambs, have thermorsgu'iatory abiiiiies quite simi'iar to adults (Âlaxander, 1361, 1362aAlaxandsr and Williams, 1962), and are able to maintain homeocherrriy when subjected to ambient temperatures as low as -10 C. Newborn caribou, due to tneir large size and weii-deveioped thermal insulation, thermoregusate with no apparent difficulty and are In thermal danger in the arctic only under wet, windy conditions (Lentz and Hart, 1960;Hart et al, 1961).…”