2002-2003 Science Planning Summary

Biology & Medicine

Dr. Polly Penhale
Program Manager


NSF/OPP 99-09422
Station: McMurdo Station
RPSC POC: Curt LaBombard
Research Site(s): Sea ice camp

Hunting behavior and energetics of free-ranging Weddell seals
Dr. Randall W. Davis
Texas A & M University
Dept. of Marine Biology
Dr. Lee Fuiman
University of Texas, Austin
Dr. Terrie Williams
University of California, Santa Cruz

Deploying Team Members: Randall W Davis . Lee A Fuiman . William H Hagey . Markus Horning . Jesse E Purdy . Matthew R Rutishauser . Theresa M Williams . Kate Willis
Research Objectives: Weddell seals (Leptonychotes weddellii) must locate and capture sparsely distributed and mobile prey in a cold, dark environment, while holding their breath and with limited access to breathing holes. These challenges form the basis of our primary question: What behavioral and energetic strategies enable free-ranging Weddell seals to forage in the antarctic fast-ice environment? In answering this question, this project's primary objectives are:

-Determine the foraging behaviors that Weddell seals use to locate and capture prey and how these behaviors vary with location, season, prey type and environmental conditions.

- Estimate the energetic costs, benefits and efficiency for different foraging behaviors, modes of locomotion and prey types.

Field Season Overview:
Soon after arriving at McMurdo, the principal investigator will identify a location on the sea ice for the field camp. From the field camp, team members will travel on snowmobiles and tracked vehicles to natural cracks in the sea ice, where they will capture adult male and non-pregnant female seals with a purse-seine net. The seals will be transported back to the field camp in a seal sled towed behind a tracked vehicle. At the field camp, team members will weigh the seals, attach an instrument package (video recorder/data logger and transmitters), and release the seal to resume natural behavior.

Each instrument packet deployment will last three to seven days. The system is programmed to remain in stand-by mode for two days while the animal returns to normal behavior. After that the video recorder is triggered when the seal descends below 100 meters (an indication that the seal has begun foraging). The data logger records depth, speed, location, ambient temperature, light level, and dissolved oxygen for up to one week.

The satellite, VHF, and sonic transmitters allow researchers to locate instrumented seals. Sealsí daily locations, accurate to one kilometer, are delivered by email to the field camp. Team members will travel by tracked vehicle, snowmobile, or helicopter, to re-capture the seals and remove the instrument package. Data and video footage will be analyzed at the field camp and at home institutions.