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

Abstract

Heat transfer through dry and wet Svalbard reindeer (Rangifer tarandus platyrhynchus) summer and winter midback fur samples was studied in a wind tunnel. A light wetting water spray simulated heavy fog, mist or light rain, while heavy soaking simulated heavy rain. Wind velocities ranged from 0 to 10 m . s -1 . Calf fur samples were from June, August and March. Adult fur samples were females from August and March. There was no evidence for increased heat loss from lightly wet fur relative to dry fur. Calm air conductance decreased for calf fur (P's < 0.05). Adult fur also decreased, however, the difference was not significant (P > 0.05). Further, wind coefficients and regressions for lightly wet fur were similar or below those for dry fur. A thin water film forming on the fur surface may have caused this. It is unlikely that a light rain, fog or mist would cause increased heat loss for Svalbard reindeer, and no increase of metabolic heat production would be needed to maintain thermoregulation. Only the simulated heavy rain dramatically raised heat loss from the fur samples examined regardless of age or season, e.g., heavy soaking increased calm air conductance for all furs (P's < 0.05). This was likely due to the addition of evaporative heat loss from the fur surface and a reduction in the amount of trapped air within the fur. Windchill was of minor importance, since wind coefficients were generally close to zero, meaning increasing wind velocity only marginally raised heat loss even with the added effect of evaporative heat loss. Rain would cause greater insulation loss than increasing wind velocity in Svalbard reindeer of all ages, with the exception of calves under one month old, which could experience dramatic insulation loss from a combination of heavy rain and windchill. Dry or wet, Svalbard reindeer fur appears to provide better insulation than fur of others of their species.

Dynamics of an introduced population of mouflon Ovis aries on the sub‐Antarctic archipelago of Kerguelen

“…In the Kerguelen archipelago, snow depth never exceeded 20 cm during our study which limits its negative effect on mouflon (Telfer and Kelsall 1984). That PI, a proxy of the number of days mouflons faced with wet conditions, decreased population growth rate supports the hypothesis of thermoregulation costs through heat loss (Cuyler and Øritsland 2004) for lambs. In our study, windchill (WCI) was not correlated to growth rate but an index combining precipitation and wind could be more relevant.…”

Light loggers reveal weather-driven changes in the daily activity patterns of arboreal and semifossorial rodents

“…3 mm. Avoidance of rain is not surprising given that wet fur can greatly increase heat loss through evaporation and, to a lesser extent, convection (Gebremedhin and Wu 2001;Cuyler and Øritsland 2004). Although we lacked precipitation data for our red squirrel study, the observed negative effect of relative humidity may have been due to the fact that high humidity is associated with precipitation events.…”

Influences of large-scale climatic variability on reindeer population dynamics: implications for reindeer husbandry in Norway

“…On the other hand, the projected increase in snowfall in higher elevated and mountainous areas may be harmful for those reindeer spending winters there, as access to lichen, their major winter forage, will be reduced. Moreover, increased precipitation as rain and sleet during calving will drain the newborn calves of heat, since the insulation property of wet pelages is greatly reduced (Cuyler & Øritsland 2004). The calves' limited ability to thermo-regulate due to limited body reserves and high surface area to body mass ratios can lead to reduced neonatal survival.…”