Meeting Abstract
61.3 Saturday, Jan. 5 Individual variability in foraging tactics of free-ranging Weddell seals MADDEN, K.M.*; FUIMAN, L.A.; WILLIAMS, T.M.; DAVIS, R.W.; University of Texas, Austin; University of Texas, Austin; University of California, Santa Cruz; Texas A&M University, Galveston kmadden@utmsi.utexas.edu
Previous studies have suggested that Weddell seals (Leptonychotes weddellii) foraging in McMurdo Sound, Antarctica specialize on a single prey, Antarctic silverfish (Pleuragramma antarcticum), using a widely-foraging, energy-maximizing foraging tactic. The degree to which diet and foraging behavior varies among individuals has not been examined. This study examined interindividual variability in diet and foraging behavior of seven female Weddell seals using video data recorders. Seals hunted from breathing holes at two locations: the coastline of a small island and offshore over deep water. Diet was established using the video record and foraging behavior was interpreted from reconstructions of three-dimensional dive paths. Two seals foraging offshore specialized on silverfish, but diet varied significantly among individuals diving near the coastline. Two of these coastal seals specialized on silverfish, while two others consumed both silverfish and benthic prey. Although benthic prey were more accessible along the coastline than offshore, silverfish, which have a higher lipid content, also required less handling to consume. Thus, it may be more energy-efficient for seals to specialize on silverfish at the coastal location despite the additional time and energy required to travel to the depths where silverfish are located. Differences were not found among the two offshore seals in either the time or energy spent searching or handling silverfish. The presence of interindividual variability in diet and foraging behavior of seals hunting from breathing holes along the coastline indicates that an increased effort should be made at these locations to measure the breadth of diet and foraging tactics and the energetic basis upon which foraging decisions are made by Weddell seals.
