title: Effects of environmental variables on surface temperature of breeding adult female northern elephant seals, Mirounga angustirostris, and pups.
abstract: Pinnipeds spend extended periods of time on shore during breeding, and some temperate species retreat to the water if exposed to high ambient temperatures. However, female northern elephant seals (Mirounga angustirostris) with pups generally avoid the water, presumably to minimize risks to pups or male harassment. Little is known about how ambient temperature affects thermoregulation of well insulated females while on shore. We used a thermographic camera to measure surface temperature (Ts) of 100 adult female elephant seals and their pups during the breeding season at Point Reyes National Seashore, yielding 782 thermograms. Environmental variables were measured by an onsite weather station. Environmental variables, especially solar radiation and ambient temperature, were the main determinants of mean and maximum Tsof both females and pups. An average of 16% of the visible surface of both females and pups was used as thermal windows to facilitate heat loss and, for pups, this area increased with solar radiation. Thermal window area of females increased with mean Tsuntil approximately 26°C and then declined. The Tsof both age classes were warmer than ambient temperature and had a large thermal gradient with the environment (female mean 11.2±0.2°C; pup mean 14.2±0.2°C). This large gradient suggests that circulatory adjustments to bypass blubber layers were sufficient to allow seals to dissipate heat under most environmental conditions. We observed the previously undescribed behavior of females and pups in the water and determined that solar radiation affected this behavior. This may have been possible due to the calm waters at the study site, which reduced the risk of neonates drowning. These results may predict important breeding habitat features for elephant seals as solar radiation and ambient temperatures change in response to changing climate.
authors.affiliation: Department of Biology, Sonoma State University, 1801 East Cotati Ave, Rohnert Park, CA 94928, USA; Inventory and Monitoring Program, Point Reyes National Seashore, 1 Bear Valley Rd, Point Reyes Station, CA 94925, USA. Electronic address: sarah_codde@nps.gov.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Codde
authors.affiliation: Science Program Lead, Pacific West Region, National Park Service, U.C. Berkeley, College of Natural Resources, 160 Mulford Hall, Berkeley, CA 94720, USA.
authors.forename: Sarah G
authors.initials: SG
authors.lastname: Allen
authors.affiliation: National Marine Mammal Foundation, 2240 Shelter Island Drive, San Diego, CA 92106, USA.
authors.forename: Dorian S
authors.initials: DS
authors.lastname: Houser
authors.affiliation: Department of Biology, Sonoma State University, 1801 East Cotati Ave, Rohnert Park, CA 94928, USA.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Crocker
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001831:Body Temperature; D001833:Body Temperature Regulation; D001947:Breeding; D005260:Female; D046048:Seals, Earless / Q000254:growth & development / Q000502:physiology*; D013472:Sunlight; D013696:Temperature; D013817:Thermography
keywords: Infrared thermography; Northern elephant seal; Thermal window; Thermoregulatory behavior