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Part C: Transfer functions for the PCAD Model

Key questions

  • How do we improve our understanding of selected transfer functions in the PCAD model to determine biological significance of behavioural response to sound exposure?
  • What are the qualitative transfer functions between change in vital rate statistics and impact to fitness?
  • Improved Transfer Functions would give the PCAD model some predictive capability. However, at the outset data existed to improve only one of the model’s four transfer functions (number 4, Vital Rates to Population Effects). Two projects were funded relative to the other three.

Summary

Project 1 (Duke and Murdock Universities) reviewed the literature available for giving transfer functions numerical values. Project 2 (University of California Santa Cruz) was a field study to collect new behavioural and physiological data aimed at improving some transfer functions. Specifically the latter project was to compare northern elephant seals and Antarctic fur seals, species that have different maternal strategies, in terms of how their foraging behaviour varied with the environment, and how animal tracking could reveal their differences in habitat use.

Project 1 suggested adding a transfer function that relates sound and physiological effects such as heart rate and blood pressure. Project 2 showed that small changes in foraging efficiency, such as those caused by noise exposure, may greatly affect body weight gain. Females with drag-inducing devices had increased metabolic rates (from added swimming effort), and increased cortisol levels. Females with lower energy gain over a foraging trip also had increased cortisol levels. The Antarctic fur seal data were not usable because predation on fur seal pups by leopard seals swamped out all other factors that drive population changes.

Objectives and methods

Projects 1 and 2

How do we improve our understanding of selected transfer functions in the PCAD model to determine biological significance of behavioural response to sound exposure?

Importance

All four Programme contracts related to the PCAD model were important steps toward giving the PCAD model some predictive capabilities. All four provided valuable background information for a project sponsored by the U.S. Office of Naval Research that further developed the PCAD model. That project used all the Programme results to create PCAD-like models for northern and southern elephant seals, the bottlenose dolphin and the northern right whale.

The ONR effort broadened our focus from noise exposure to any form of temporary disturbance. The resultant model is now referred to as Population Consequences of Disturbance, PCoD. Effectively, the original Programme projects on PCAD stimulated more detailed work which led to new models that are becoming usable tools in animal management.

Links to other research

See the ONR website for reports of the ONR panel on the improved PCoD models.

Institutions/PIs

  • Project 1: Duke University (Douglas Nowacek) and Murdock University, Australia (Lars Bejder)
  • Project 2: University of California, Santa Cruz (Dan Costa)

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