NSFGEO-NERC Collaborative Research: Effects of a changing climate on the habitat utilization, foraging ecology and distribution of crabeater seals

We propose to investigate the differences in the trophic ecology, distribution and foraging success of crabeater seals across a latitudinal gradient along the western Antarctica Peninsula (wAP). As a consequence of global climate change and local environmental processes, the atmosphere and oceans along the wAP are rapidly changing. Our study will enhance our ability to understand how the entire krill-dependent community of large predators will respond to the projected environmental changes. Furthermore, we have ecological baseline data from 20 years ago on movement patterns, diving behavior, feeding behavior, distribution and abundance for the species, as well as historical data and samples from the mid-1990s, providing us with a unique opportunity and advantageous position to detect changes in the ecology of this conspicuous Antarctic mesopredator and the extended predator community.
The crabeater seal (Lobodon carcinophaga) is the most important predator of Antarctic krill Euphausia superba in Antarctic waters. This is due to its high degree of ecological specialization, large abundance and biomass, and high metabolic demand. Its high dependence on a single prey resource, combined with being an obligate inhabitant of the pack ice, makes the crabeater seal an excellent species to examine changes in krill distribution as well as potential changes in the structure of the entire ecosystem: the horizontal distribution of the seal is determined by the distribution of krill, and similarly the seals diving behavior provides insights into the vertical distribution of this euphausiid in the water column.
Given the dichotomy in the daily habitat requirements of the crabeater seal, we aim to evaluate whether these previously-overlapping habitats are now separating in time and space along the western Antarctic Peninsula. Given the latitudinal differences in sea ice timing and extent. As well as the extreme dependence of crabeater seals on krill, we expect that individuals in the northern wAP have modified their foraging behavior and incur in elevated energetic costs as opposed to animals in the southern wAP. Alternatively, crabeater seals could have modified their habitat usage patterns and/or their diet in response to the changing climate along the wAP.
We will use traditional aerial surveys combined with new technologies (UAS and satellite imagery) to census the population of seals in the wAP through a collaboration with BAS. The aerial surveys will provide a benchmark against which we can validate the new data obtained from these platforms, which are logistically easier and more cost-effective. The tracking studies will also provide concurrent data on haulout patterns of crabeater seals that will be used to correct the survey data for the proportion of individuals at sea1. The survey and tracking data will be utilized to first determine if the crabeater seal population has declined and or moved south in response to declining sea ice. Second, develop habitat models of the species distribution to define the variables that influence where the animals are eating versus where they are hauling out, determine how these habitats differ and predict the spatio-temporal co-occurrence of these environmental conditions.