Download Spatial Ecology of Humpback and Minke Whales Off the Western Antarctic Peninsula Book in PDF, ePub and Kindle
The Western Antarctic Peninsula (WAP) is a biologically rich area supporting a persistent and large standing stock of Antarctic krill and predators, including baleen whales. Krill demography and survival is tied directly to physical forcing, and recruitment is profoundly influenced by climate variability. Based on known changes in sea ice conditions in the WAP, it is likely that krill population levels in the region are in jeopardy. Due to their dependence on a single prey item heavily influenced by physical forcing, the dynamics of krill predators, such as baleen whales, are tightly coupled with variation in krill availability. To date, however, few studies link the distribution of prey to the spatial ecology of baleen whales in this ecosystem. This dissertation aims to (1) elucidate spatially explicit relationships between baleen whales, environmental variables, and concurrent prey measurements using classification trees (CART), generalized additive models, and Mantel's tests, (2) test ecological hypotheses regarding how sympatric humpback and minke whales partition resources to avoid inter-specific competition using CART and generalized linear models, and (3) investigate trends in spatial relationships between baleen whales, the marginal ice edge, and krill abundance over a time series using zero-inflated Poisson regression models. I use whale sightings and environmental variables collected during long-term ecological research cruises off the WAP from 1993-2004, and Southern Ocean Global Ocean Ecosystems Dynamics Program (SO GLOBEC) cruises from 2001-2002. Using these approaches, the distribution and relative abundance of baleen whales in summer was most related to proximity to the ice edge and, secondly, to krill abundance. In fall, whales primarily target krill aggregations and then physical features which aggregate prey. I find evidence suggesting sympatric humpback and minke whales avoid interspecific competition through resource partitioning. Minkes associate with deeper krill patches, and smaller patches of differing sized krill than humpbacks. Across years, the relative abundance of whales relates to differences in the dominant size class of krill present. These findings can be valuable to organizations committed to conserving and managing whale populations, researchers interested in understanding predator-prey dynamics, and efforts to model effects of climate change and variability on the Antarctic marine ecosystem.