Movements of Adélie Penguins in the Western Antarctic Peninsula Region
William R. Fraser1, Christine A. Ribic2,
Donna L. Patterson1, and Erik W. Chapman3
Oceans Research Group, Sheridan, Montana, USA.
2USGS Wisconsin Cooperative Wildlife Research Unit, Dept. Wildlife Ecology, University of Wisconsin, Madison, Wisconsin, USA.
for Coastal Physical Oceanography, Old Dominion University, Norfolk, Virginia, USA.
transition from summer to winter over the western Antarctic Peninsula (WAP)
shelf region is characterized by a substantial and significant decrease in
primary production and phytoplankton biomass.
This results in a food web that during polar winter is decoupled from
the more common summer state of high water column primary production. Despite these conditions, however, a majority
of apex predators remain in the WAP during winter, including several species
whose numerical abundance alone accounts for much of the regional apex predator
biomass. To investigate some of the
processes that may sustain these large predator populations during winter, we
examined the foraging movements of Adélie penguins (Pygoscelis
adeliae) in the U.S. Southern Ocean Global Ocean
Ecosystem Dynamics (U.S. SO GLOBEC) study grid near Marguerite
Bay. This was done by using
Platform Terminal Transmitters (PTTs) attached to
penguins during cruises in autumn/winter 2001 and 2002, and tracking their
positions using the ARGOS satellite
constellation. In 2001, 8 and 12 PTTs were deployed
on male and female penguins, respectively. The tags recorded penguin locations
for an average of 62 days (s.e.
= 34 days) between 8 May and 3
December 2001. In 2002, 21
and 15 PTTs were deployed on male and female
penguins, respectively. These tags
recorded locations for an average of 73 days (s.e. = 50 days) between 12 April 2002 and 29
January 2003. Winter sea ice
conditions were significantly different between the two years and this affected
the area over which penguins were able to forage within the study grid. In winter 2001, the ice edge extended north
only to about 64 degrees south latitude while in winter 2002, the ice edge
extended beyond 61 degrees south latitude, or the northern tip of the WAP. During both winters, penguin foraging locations
converged on a large coastal polynya found at the
southern end of Adelaide Island,
However, during winter 2002 the Adélie penguins, females in particular, were
able to extend their foraging to other polynyas
within and beyond the SO GLOBEC study grid.
Apart from providing open water, these polynyas
were in all cases associated with unique, deep bathymetry, higher prey
concentrations and large numbers of other top predators. These results suggest
that polynyas along the WAP are important winter
foraging areas for Adélie penguins and, possibly, other top predators; sea ice
is one of the key variables mediating access to regions in the WAP where
predictable winter prey concentrations may occur; and female Adélie penguins
may be particularly dependent on heavy sea ice conditions to forage
abstract, and author list received on 06/28/05.