Dissertation Research: Marine Mammal Feeding Guilds: Diversity and Overturn Through the Cenozoic
Blaire Van Valkenburgh and Peter J. Adam University of California, Los Angeles
Marine mammals constitute a diverse and unrelated assemblage of animals with an obligate dependence on marine resources. Carnivorous marine mammals include cetaceans (whales and dolphins), pinnipeds (seals and sea lions), and sea otters. Within these groups are a wide variety of feeding strategies that can be distinguished based on functional characters of the skull and teeth as well as models that predict scaling relationships between predator and prey body sizes. This project will document the diversity of feeding types and body sizes in marine mammals over the past 50 million years, and infer incidence of competition and replacement within and between marine mammal communities at both local and global scales.
Temporal and spatial distributions of living and fossil marine mammals will be determined from the literature and a survey of museum collections. Fossil taxa will be categorized into one of four broad feeding strategies observed in modern marine mammals based on functional skull and tooth characteristics. These strategies include masticatory (e.g., sea otters), piercing (e.g., most dolphins), suction (e.g., walrus), and filter feeding (e.g., baleen whales). Within each strategy, feeding regimes of fossil taxa will be further resolved into more descriptive subcategories (e.g., pelagic squid-eating suction feeders versus benthic bivalve-eating suction feeders). Methods for predicting body size in fossil taxa will also be developed and applied to models of predator:prey body size relationships to establish probable prey sizes taken by fossil marine mammals. Distribution and diversity data will be further interpreted in relation to taphonomic (preservational) biases and major paleoceanographic events of the Cenozoic. Patterns of turnover and convergence in feeding strategies among and within various marine mammal lineages will reveal cases of competition for food resources and its effects. Taken together, these data will contribute to a much better understanding of dynamic Cenozoic marine communities.
This study is the first comprehensive examination of any Cenozoic marine vertebrate community. Although interpretation of feeding strategies in fossil taxa is a common practice, interpretation of these data in a broader paleoecological sense is rarely realized. This study not only provides a comprehensive summary of ecological roles of marine mammals through time; it also provides a framework from which ecological roles of other large marine predators (e.g., sharks, squid) can be interpreted. All data will be archived in the public domain for use by other researchers. The investigators will develop undergraduate research projects and activities for under-performing high schools in urban Los Angeles based on this research project.
