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Contact Us
Bob Garrott & Jay Rotella
Department of Ecology
308 Lewis Hall
Montana State University
Bozeman, MT 59717-3460

Tel: (406) 994-4548
Fax: (406) 994-3190

> Department of Ecology
Weddell Seal Population Dynamics
in
Erebus Bay, Antarctica

The Demographic Consequences of Environmental Variability and Individual Heterogeneity in Life-history Tactics of a Long-lived Antarctic Marine Predator

reading tags

Project Description & Data

The Ross Sea, a geographically well-defined embayment of the Antarctic continental shelf, provides an outstanding scientific opportunity in the Southern Ocean for gaining insights into marine ecosystem processes due to its unique combination of attributes. Of note, the Ross Sea is one of the most pristine marine systems on the planet. An intensive study of a breeding population of Weddell seals in the Erebus Bay region of eastern McMurdo Sound at the southern extent of the Ross Sea was initiated in 1968. The study of the population represents one of the longest continuous field investigations of a long-lived mammal in existence. Because Weddell seals are large, marine predators, information on the population provides an excellent complement to other studies on other aspects of the marine system (for example, studies of penguins, fish, and marine invertebrates).  Further, the long-term data for Weddell seals provide a valuable benchmark for monitoring potential changes in the future. This is especially valuable given interests in potential effects of climate change and possible effects of recently established fishing operations in the area.  

Over the 42-years of this study, more than 20,586 animals have been tagged, and over 180,000 re-sightings have been logged in the database. Emphasis has consistently been on maintaining
and enhancing annual demographic data through the use of mark-recapture techniques.  Because all pups born within the study area have been tagged since 1973 and because this species
demonstrates strong philopatric behavior, ~80% of the seals are marked and >65% of the individuals in the population are currently both marked and of known age.

This study and the database accrued through nearly four decades of intensive effort provide a
strong foundation and unique opportunity to extend our ecological knowledge of population and
ecosystem processes. Inferences from this multi-decadal study extend beyond the Ross Sea and contribute to a broader body of knowledge about the evolution of life-history strategies and population dynamics of long-lived organisms in variable environments. Such information is vital to understanding and conserving many other animal populations. In our current work we continue to build on this foundation with two lines of investigation that combine (1) mark-resight and other advanced analytical tools to describe and understand population processes and (2) studies of seal mass dynamics to link demographic variability with ecosystem processes.

To meet the objective of our current research agenda and to test the hypotheses of primary interest, we use a variety of approaches and methodologies that can be categorized into three general initiatives: 1) continuation of annual seal tagging and mark-recapture surveys to maintain continuity of the long-term demographic database, 2) comprehensive analyses and integration of the long-term demographic database using recently developed analytical approaches, and 3) collection and analyses of individual body mass dynamics and the development of multiple regression models to evaluate the hypotheses posed.

Data on animals tagged are available here.  The data can be used to obtain information on:
  1. Individual tag information including the most recent tag numbers and colors,
  2. Year when each animal was tagged,
  3. Animal sex,
  4. Animal age when tagged (for animals tagged as pups, age can be calculated), and
  5. Date the animal was last observed.
Data used in two recent papers are available here The papers are:
  1. Chambert, T., J.J. Rotella, and M.D. Higgs.  In Press. Use of posterior predictive checks as an inferential tool for investigating individual heterogeneity in animal population vital rates. Ecology & Evolution.
  2. Chambert, T., J.J. Rotella, M.D. Higgs, and R.A. Garrott. 2013. Individual heterogeneity in reproductive rates and cost of reproduction in a long-lived vertebrate. Ecology and Evolution 3:2047-2060.
If you have questions about the project or seal database, please contact Bob Garrott or Jay Rotella by e-mail, surface mail, or phone.




Field camp for seal studies

View Text-only Version Text-only Updated: 10/05/2014
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