Weddell
Seal Population Dynamics
in
Erebus Bay, Antarctica Interactions
of Environmental Variability, Life History Traits,
and Demography in an Apex Antarctic Predator
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 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 42-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-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.
