Meeting Abstract
67.5 Sunday, Jan. 6 Energetic costs of a unique thermoregulatory behavior: Jughandling in northern fur seal (Callorhinus ursinus) pups resting at sea MOSTMAN-LIWANAG, H.E.*; WILLIAMS, T.M.; GULLAND, F.; ROWLES, T.; COSTA, D.P.; Univ. of California, Santa Cruz; Univ. of California, Santa Cruz; The Marine Mammal Center, Sausalito, CA; National Marine Fisheries Service, Silver Spring, MD; Univ. of California, Santa Cruz mostman@biology.ucsc.edu
Behavioral thermoregulation is a ubiquitous and important strategy for reducing the energetic costs of maintaining thermal balance. As small endotherms in the highly conductive marine environment, northern fur seal pups face particularly high thermoregulatory costs. While resting at sea, northern fur seals often perform a behavior called jughandling, in which they float with one foreflipper held between both hind flippers above the water. The purpose of this behavior is unknown, but popular hypotheses include opposing thermoregulatory consequences: either animals remove flippers from the water to avoid heat loss to cold water, or they position flippers in the air to increase convective heat loss when overheated. To examine the consequences of this behavior, we measured metabolic rate at rest (RMR) and during jughandling (JMR) for three northern fur seal pups over a range of water temperatures (Twater=2.5-25°C). RMR averaged 9.1±1.5 mLO2·kg-1·min-1 in Twater=8-25°C. Lower critical temperature, identified by an increase in RMR, was 8.3±1.5°C. Jughandling behavior resulted in a characteristic response, in which metabolic rate increased above that associated with activity, then exhibited a first-order recovery curve. Once recovered, JMR (12.8±2.7 mLO2·kg-1·min-1) was significantly greater than RMR at water temperatures within the thermal neutral zone, but less than RMR at colder water temperatures. We find that this unique behavior is energetically costly to northern fur seal pups, but may help to mitigate thermal costs below the lower critical temperature.
