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Environmental Perturbations, Behavioral Change, and Population Response in a Long-Term Northern Elephant Seal Study

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A major challenge in marine mammal conservation and management is to understand how behavioral responses affect populations. To address this challenge, the National Research Council established the Committee on Characterizing Biologically Significant Marine Mammal Behavior. This committee developed a framework for analyzing the population consequences of acoustic disturbance, or PCAD NRC 2005. The PCAD framework defines a series of transfer functions which describe how behavioral responses to sound affect life functions, how life functions are linked to vital population rates, and how changes in vital rates cause population change. Implementing the concepts of transfer functions which link behavior to population change, however, requires substantial long-term data on individual animals and population size, and there are few marine mammal populations where quantifying the functions is plausible. Funding from this grant has allowed us to extend and improve a four-decade study of northern elephant seal populations in California, aiming specifically to quantify key linkages within the PCAD model. Since 1968, several thousand individual seals have been tagged and tracked for their lifetimes, and several hundred of those have been weighed or outfitted with telemetry devices in order to document pelagic foraging behavior and body condition. Recent advances in telemetry and our understanding of foraging behavior and body condition allow us to extend this study into the future with improved methods, and with our current funding we have maintained and advanced a classic long-term study of a vertebrate population. Specifically we have collected data to answer two general questions 1 How closely coupled are short term changes in foraging behavior to adult fecundity and survival and 2 Does this link vary with environmental perturbations such as the El Nino Southern Oscillation ENSO

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  • Ecology
  • Biological Oceanography

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