> Department of Ecology
Seal Population Dynamics
Erebus Bay, Antarctica
Demographic Consequences of Environmental Variability and Individual
Heterogeneity in Life-history Tactics of a Long-lived Antarctic Marine
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
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
animals tagged are available here.
The data can be used to obtain information on:
Data used in
two recent papers are available here.
The papers are:
- Individual tag information including the
most recent tag numbers and colors,
- Year when each animal was tagged,
- Animal sex,
- Animal age when tagged (for animals
tagged as pups, age can be calculated), and
- Date the animal was last observed.
have questions about the project or seal database, please
contact Bob Garrott or Jay Rotella by e-mail, surface mail, or phone.
- 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
- 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