Behavioral Evidence of Thermal Stress From Overheating in Uk Breeding Gray Seals

Abstract

Gray seals (Halichoerus grypus) in the UK exhibit clear preferences for pupping close to pools of water on inland breeding sites. The reasons for this are unclear as seals are thought to derive all their water requirements from the metabolism of fat. Likewise, the prospect of seals overheating during the UK's cool, damp, autumnal breeding seasons, has seemed unlikely, but has not been previously explored. Here, we provide preliminary behavioral evidence of thermal stress in female gray seals breeding on the island of North Rona, Scotland. Video footage provided measures of proximity to, and the proportion of animals bathing in, pools in relation to meteorological data (temperature, mean sea‐level pressure, rainfall, wind speed and direction) on four dates spread through a single breeding season. The proportion of females close to pools increased with pressure (warmer, drier conditions) and decreased on wetter days. In addition, analyses of colony‐wide patterns of seal dispersion showed that females tended to be closer to pools of water at higher pressures and temperatures and at lower wind‐speeds. These results provide the first evidence of thermal stress and behavioral thermoregulation through access to pools of water in a phocid breeding in temperate autumnal conditions.

Environment and activity affect skin temperature in breeding adult male elephant seals (Mirounga angustirostris)

“…The strong impacts of solar radiation on T S are consistent with previous suggestions outlining the importance of this variable in affecting thermoregulatory behavior in pinnipeds (Beentjes, 2006;Twiss et al, 2002;Campagna and Le Boeuf, 1988;White and Odell, 1971). Direct exposure to solar radiation results in not only the animal absorbing heat but also the warming of the surrounding substrate, lowering any heat gradient and possibly adding to the heat gain of an animal through conduction (Campagna and Le Boeuf, 1988).…”

“…Physiological or behavioral thermoregulation mechanisms often drive reproductive behavior in pinnipeds. Female New Zealand fur seals, southern sea lions, Juan Fernandez fur seals and grey seals are known to migrate to tide pools, the shoreline or directly into the ocean during periods of increased solar radiation and air temperature (Twiss et al, 2002;Francis and Boness, 1991;Campagna and Le Boeuf, 1988). Males defending territories with access to water, in which greater numbers of females aggregate, enjoy increased copulatory success compared with that of males guarding waterless areas (Francis and Boness, 1991;Campagna and Le Boeuf, 1988).…”

“…However, White and Odell discovered that physiological mechanisms such as vasodilation and evaporatory cooling might be inadequate forms of heat dissipation in northern elephant seals (White and Odell, 1971). The presence of direct solar radiation might prevent the effectiveness of this avenue for heat loss (Twiss et al, 2002), particularly in highranking males, which secure central positions in harems and cannot retreat to the water as a thermoregulatory aid without ceding access to females.…”

Environment-driven changes in terrestrial habitat use and distribution of the Galapagos sea lion

“…This behavioral thermoregulatory mechanism, described for the first time in a tropical pinniped in the present paper, the GSL, is shared by other temperate pinnipeds. Southern sea lions Otaria flavescens, Juan Fernandez fur seals Arctocephalus philippii, and grey seals also use behavioral thermo regulatory mechanisms, demonstrating movements towards shorelines and into the ocean in summers, when temperatures are high (Campagna & Le Boeuf 1988, Francis & Boness 1991, Twiss et al 2002. Our results are in agreement with Wolf et al (2005), who suggested that GSL habitat preferences are linked to thermoregulatory requirements.…”

“…Thus, the thermoregulation response is especially challenging for pinnipeds due to the differences in thermal fluxes in both environments and also because their large body size limits the effectiveness of surface heat loss (Norris et al 2010). Behavioral responses such as the thermoregulation mechanism are known to be important drivers of haul-out patterns in many temperate pinniped species (White & Odell 1971, Witthow et al 1971, Odell 1974, Campagna & Le Boeuf 1988, Francis & Boness 1991, Twiss et al 2002. However, little is known about temporal variations in haul-out behavior and thermoregulation of pinnipeds inhabiting low latitudes.…”