Thermoregulation in Steller sea lions: an experimental approach.

The exchange of heat between a homeothermic animal's body and it's environment can be expressed in terms of heat flow, also called heat flux, typically stated in units of energy transferred per surface area (W m^-2).

For details on the Heat Flux Sensors, check out our <SENSOR> pages in the <TECHNOLOGY> section. For definitions of term related to thermoregulation and heat flow, check out the <GLOSSARY> in the <TECHNOLOGY> section.

This study - run by WFSC Masters candidate Kate Willis - is testing how thermal energy transfers between Steller sea lions and their environment can be quantified using animal-borne Heat Flux Sensors (HFS) (Thermonetics Corp., San Diego, CA). The specific objectives of the work proposed here are to:

1) Measure how heat flux in stationary and free-swimming animals changes in air and water of different temperatures and throughout different seasons.

2) Measure the major pathways of heat flux in Steller sea lions using an infra-red thermal imaging camera (ThermaCAM PM695, FLIR Systems) in order to analyze the variability of major heat flux pathway locations, and to determine optimal location for the heat flux sensors.

The image below is a thermal image of Woody on a rock surrounded by water in the habitat area at the Alaska SeaLife Center, Seward, AK.

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3) Use data collected from heat flux sensors and an existing physiological thermoregulation model (Roscow, 2001) to estimate whether Steller sea lions are likely to encounter thermoregulatory problems when foraging in cold water.

In the image below, Kate is seen completing the attachment of the heat flux recording system to Woody, a male Steller sea lion, at the Alaska SeaLife Center. Under anesthesia, the sensors are glued to small shaved patches of skin. The four sensors are connected to the recorder via cables and waterproof connectors. The cables are held down by strips of neoprene glued to the fur. The black recorder is bolted to a thin orange baseplate, which in turn is attached to a neoprene patch. The patch is glued to the dorsal fur.

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The image below shows Woody in the sea lion habitat, carrying the complete system.

The ultimate goal of this study will be to quantify conductive and convective heat losses over a range of water temperatures, water flow speeds, and animal behaviors. This will in turn significantly enhance our understanding of heat flux in Steller sea lions and its relationship to other physiological processes. Understanding such potential physiological relationships might contribute to determining causes for the continuing decline of the Steller sea lion population.

Work is being conducted using captive Steller sea lions held at the Vancouver Aquarium in Vancouver, British Columbia, Canada and at the Alaska SeaLife Center in Seward, Alaska.

PUBLICATIONS from this project:

1. Willis K, Horning M (2005)
   A novel approach to measuring heat flux in swimming animals.
   Journal of Experimental Marine Biology and Ecology, Vol. 315 (2): 147-162. Full text (pdf).
   
   
2. Willis K, Horning M, Rosen DAS, Trites AW (2005)
   Spatial variation of heat flux in Steller sea lions: evidence for consistent avenues of heat exchange along the body trunk.
   Journal of Experimental Marine Biology and Ecology, Vol. 315 (2): 163-175. Full text (pdf).

This project was supported by:

• A National Science Foundation Graduate Research Fellowship to Kate Willis
• An Alaska SeaLife Center Research Grant to M. Horning and Kate Willis
  (this grant is sponsored by NOAA funding to the ASLC)
  
• A PADI Aware Foundation grant to Kate Willis
  
• Logistic support by the Marine Mammal Research Unit at the University of British Columbia, Vancouver, BC; and by the Vancouver Aquarium. The operations of the UBC MMRU Steller sea lions at the Vancouver Aquarium are sponsored by NOAA funding to the North Pacific Universities Marine Mammal Research Consortium (NPUMMRC).
  

This project / work is being / was carried out under one or more of these permits:
TAMU ULACC AUP# 9-170, 9-171, 2001-112
ASLC IACUC AUP# 00-004, 00-006, 01-001
MMPA permit # 881-1443 to the ASLC

More about Stellers
The NMML/NMFS Steller page

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