OUR WEDDELL SEAL ECOLOGY RESEARCH

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 provides a valuable opportunity for a contrasting study of the ecological consequences of global climate change: while most regions of the globe are experiencing warming trends, the Ross Sea is experiencing a general cooling of air temperatures and a consequent lengthening of the sea-ice season. 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 and represents one of the longest continuous field investigations of a long-lived mammal in existence.

Over the 43 years of this study, more than 20,100 animals have been tagged, and 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-resight techniques. Because all pups born within the study area have been tagged since 1973 and because this species demonstrates strong philopatric behavior, approximately 80% of the seals are marked and more than 65% of the individuals in the population are currently both marked and of known age.

This study and the database accrued over more than 40 years 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-resight 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 as of 2010 can be downloaded 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.

If you have questions about the project or seal database, please contact Bob Garrott or Jay Rotella by e-mail, surface mail, or phone.