Hungry, Hungry Pinnipeds The Comparative Feeding Morphology of Phocid Seals

Meeting Abstract

142.4  Monday, Jan. 7  Hungry, Hungry Pinnipeds: The Comparative Feeding Morphology of Phocid Seals KIENLE, SS; San Diego State University

Pinnipeds (seals, sea lions, and walruses) evolved specific feeding strategies to capture and consume prey underwater. Most are generalist feeders, employing pierce or suction feeding. Grip-and-tear and filter feeding are specialized strategies exhibited only by the crabeater seal and leopard seal. Phocids (true seals) are a model group for this study as they are the most diverse pinniped lineage with 18 extant species and employ all four feeding types. The objectives were 1) to determine the feeding strategies used by extant phocids, and 2) to compare generalist and specialist feeding strategies in an evolutionary and ecological context. Three dimensional landmark data were collected from 220 specimens representing all extant phocids. A total of 58 cranial and 24 mandibular landmarks were taken per specimen. Principle Component Analysis and Discriminate Function Analysis were performed. Coalescent-based methods were utilized to generate a molecular phylogeny, and comparative phylogenetic methods determined the ecological factors driving the evolution of each feeding type. The results show that grip-and-tear and filter feeders have evolved distinct feeding characteristics. These morphological adaptations have allowed crabeater and leopard seals to exploit novel niches. However, it has resulted in increased dependence on one or a few prey sources, which could affect survival if prey abundance changes. In contrast to previous studies, the generalist feeding strategies do not correlate with predicted feeding characters. These findings suggest that pierce and suction feeding are not distinct feeding categories or that there are more feeding categories than hypothesized. These results provide a framework to better understand the feeding modes employed by phocids, enabling us to predict how phocids will respond to changing environments.

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