Dear colleagues:
We are happy to announce the publication of two studies on thermoregulatory
abilities of northern fur seals in Marine Mammal Science.
Dalton AJM, Rosen DAS, Trites AW (2014) Broad thermal capacity facilitates the
primarily pelagic existence of northern fur seals (Callorhinus ursinus). Marine
Mammal Science 30: 994-1013
Rosen DAS, Trites AW (2014) Thermal limits in young northern fur seals,
Callorhinus ursinus. Marine Mammal Science 30: 1014-1028
Electronic copies can be obtained by writing me at: [email protected]
Regards,
Dave Rosen
Abstract: Dalton et al.
Thermoregulatory capacity may constrain the distribution of marine mammals
despite having anatomical and physiological adaptations to compensate for the
thermal challenges of an aquatic lifestyle. We tested whether subadult female
northern fur seals (Callorhinus ursinus) experience increased thermoregulatory
costs in water temperatures potentially encountered during their annual
migration in the Bering Sea and North Pacific Ocean. Metabolic rates were
measured seasonally in 6 captive female northern fur seals (2.75–3.5 yr old) in
ambient air and controlled water temperatures of 2°C, 10°C, and 18°C. Rates of
oxygen consumption in ambient air (1°C–18°C) were not related to environmental
temperature except below 2.5°C (winter only). However, metabolism was
significantly higher during the fall seasonal trials (September–October)
compared to other times of year, perhaps due to the costs of molting. The fur
seals appeared thermally neutral in all seasons for all water temperatures
tested (2°C–18°C) except during the summer when metabolic rates were higher in
the 2°C water. Comparing this broad thermal neutral zone to the average sea
surface temperatures potentially encountered during annual migrations indicates
wild fur seals can likely exploit a large geographic area without added thermal
metabolic costs.
Abstract: Rosen and Trites
The thermoregulatory abilities of northern fur seals (Callorhinus ursinus)
during their first two years in the frigid waters of the North Pacific Ocean
may limit their geographic distribution and alter the costs for exploiting
different species of prey. We determined the thermoneutral zone of six young
northern fur seals by measuring their metabolism in ambient air and controlled
water temperatures (0°C–12°C) from ages 8 to 24 mo. We found that the ambient
air temperatures within our study (overall 1.5°C–23.9°C) did not affect resting
metabolic rates. Calculated lower critical temperatures in water varied between
3.9°C and 8.0°C, while an upper critical temperature in water was only
discernible during a single set of trials. These thermal responses provide
insight into the possible physiological constraints on foraging ecology in
young northern fur seals, as well as the potential energetic consequences of
ocean climate change and altered prey distributions.
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