2002-2003 Science Planning Summary

Biology & Medicine

Dr. Polly Penhale
Program Manager

BO-009-O

NSF/OPP 02-25110
Station: McMurdo Station
RPSC POC: Kirk Salveson
Research Site(s): Turtle Rock, Hutton Cliffs, White Island, Scott Base, sea ice camp, Cape Royds, Cape Evans, field camp at Big Razorback

Patterns and processes: Dynamics of the Erebus Bay Weddell seal population
Dr. Robert A. Garrott
Montana State University Bozeman
Ecology
rgarrott@montana.edu
Dr. Jay Rotella
Montana State University, Bozeman

Deploying Team Members: Christine V Alfano . Michael F Cameron . Robert A Garrott . Gillian Hadley . Darren Ireland . Jay J Rotella . Brent S Stewart . Jeffrey Warren . Pamela K Yochem
Research Objectives: The study of the Erebus Bay Weddell seal population in eastern McMurdo Sound was initiated in 1968 and represents one of the longest intensive field investigations of a long-lived mammal in existence. Some 15,636 animals have been tagged, with 144,927 resighting records in the database.

This season, researchers intend to build on this foundation with two lines of investigation that combine the long-term database with new field initiatives. They will maintain the continuity of the demographic data by annually marking all pups born, replace lost or broken tags, and perform multiple mark-recapture censuses. The new data will be combined with the existing database, and a complex series of demographic analyses will be performed. These analyses will allow researchers to test hypotheses about population regulation, as well as temporal and spatial patterns of variation in vital rates among colonies within the population.

A sample of adult female seals and pups will be weighed, and body morphometrics will be obtained using digital photography combined with image analysis software. Regression equations will be developed from these data to predict body mass. At each major colony within Erebus Bay, these regression equations will be used to estimate annually the parturition and weaning mass of a large sample of adult female seals and their associated pups. Project team members will also use satellite imagery to track sea-ice extent in McMurdo Sound. The extent of sea ice affects regional primary productivity, which may increase marine resources, thereby having a positive effect on foraging efficiency and leading to increased body mass. These data, combined with the large proportion of known-aged seals in the current study population (more than 60%), will comprise a powerful database that can be used to test specific hypotheses.

Learning about the mechanisms that limit and/or regulate Weddell seal populations and the specific biophysical links between climate, oceans, ice, and antarctic food webs can make an important contribution toward understanding pinniped population dynamics, as well as add to the understanding of population, community, and ecosystem patterns and processes. Continuation of this long-term study may also contribute toward understanding the possible detrimental impacts of human activities such as global climate warming and the commercial exploitation of antarctic marine resources. This study can contribute significantly to the development and testing of new research and analytical methodologies that will almost certainly have other applications.


Field Season Overview:
Researchers will set up a camp of sea ice huts near Big Razorback Island, which will serve as their base for the field season. Within the study area, stretching from Cape Evans to Pram Point, all newborn pups will be tagged and tags will be replaced on previously marked adults. Team members will travel by snowmobiles and tracked vehicle to conduct a weekly census to count and record the tag number of all seals. At Big Razorback, a remotely operated underwater camera will be used to examine the spacing patterns of adult females on the ice surface and underwater.

The team members will travel by helicopter and Twin Otter aircraft to tag seals and collect information on marked seals outside the study area. This will include areas around Ross Island, parts of the continental coast on the western side of McMurdo Sound, Cape Washington, Markham Island, and White Island. The researchers will attach satellite-linked radio transmitters to seals to investigate the emigration of weaned pups and adults, as well as monitor their movements on the ice and underwater. Team members will travel by helicopter and use radio telemetry to track and locate radio-tagged seals.

A new program for estimating the mass (weight) dynamics of adult female seals and their pups will be initiated this season. The first seasonís work will primarily involve technique development and testing. Each seal will be photographed from several angles and weighed on a livestock scale mounted on a sled. From these data, researchers will develop equations to estimate mass based on body measurements. Next season the team will collect sequential mass measurements of seal mother and pup pairs at all colonies. Ultimately, mass dynamics will be correlated with other factors such as survival, reproduction, colony, sea ice conditions, and climate.

The research team will also collect blood, scat, and diet samples for collaborative work with scientists studying Weddell seal blood chemistry, health parameters, blood parasites, and diet. In conjunction with these studies, the researchers will continue their investigations of anesthetic agents used in handling Weddell seals. Frozen seal blood and tissue samples will be prepared in the Crary lab and returned to the home institution for further studies.