Behavioral Ecology of Cetaceans: The Relationship of Body Condition with Behavior and Reproductive Status

Dr. Patrick Miller | University of Saint Andrews

RC-2337

Objective

The risk of harm to cetaceans from underwater noise is an important environmental and regulatory issue faced by the Department of Defense, in particular the Navy. Long-term consequences of disturbance are particularly difficult to quantify.  Noise may reduce foraging rates and thereby body condition, which is a good predictor of offspring survival and reproductive success. Body condition influences how animals trade-off foraging and anti-predator behaviors, and it modulates responses to human disturbance. Thus, behavioral ecology studies of how body condition relates to the risk and consequences of acoustic disturbance in cetaceans should be a high priority. Current methods for estimating body condition in cetaceans, however, are descriptive or do not measure full-body fat (lipid) stores.

This project will validate, establish, and use a novel, non-invasive method to measure total body lipid-stores of free-ranging cetaceans. The cornerstone of the approach is to measure body density of tagged animals, which corresponds to lipid content (fat stores) in mammals because lipids are less dense than other compartments (e.g., bone, skin). Body density of individual whales will be cross-compared to three independent measurements of body condition: (1) lipid content in blubber biopsy samples, (2) concentrations of adipocyte-related hormones that in other mammals are signals of the size of body energy stores, and (3) body dimensions measured using a high-frequency underwater imaging sonar system. How body condition varies as a function of the reproductive status of females (pregnant, nursing, or resting) also will be quantified.

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Technical Approach

The two target species, Northern bottlenose (Hyperoodon ampullatus) and humpback whales (Megaptera novaeangliae), will be studied in established field sites in the North Atlantic Ocean. Body density will be calculated using analysis of underwater gliding performance from dive data recording tags attached to animals using suction cups. This method, demonstrated in deep-diving Hyperoodon in an earlier limited-scope pilot study ( RC-2113), will be applied to shallower-diving Megaptera using state-of-the-art statistical techniques. Lipid-content body condition in the tested species will be compared to concentrations of lipids and lipid-related hormones within blubber biopsy samples and with body-dimension measurements using high-frequency scanning sonar. High-resolution tag data will enable traditional analyses of foraging effort, energetic performance, and anti-predator behaviors. Reproductive state of photo-identified females will be assessed via calf presence and analysis of hormones in biopsy samples and blow-expirate.

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Benefits

Measurement of body density via analysis of gliding performance is a novel approach that provides quantitative, replicable measures of total body lipid body condition of living cetaceans. The results of this study will therefore establish and validate an innovative technique to measure body condition in cetaceans and enable examining the interplay of body condition with foraging and anti-predator behaviors and the reproductive status of females. This study will advance the ability to predict and measure the potential impact of human disturbance on individuals and populations of cetaceans. 

Results of the study will be transitioned on an ongoing basis to the Office of Naval Research (ONR)-funded working group PCAD (Population Consequences of Acoustic Disturbance). Tools and techniques to measure body density will be shared with researchers studying the reactions of cetaceans to sonar in behavioral response studies, under the ONR-funded projects 3S and MOCHA. The results of the study, and all data-sets, will be transitioned to the Sea Mammal Research Unit instrumentation group to design a tag to measure and telemeter body condition of cetaceans over long periods. (Anticipated Project Completion - 2018)

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Points of Contact

Principal Investigator

Dr. Patrick Miller

University of Saint Andrews

Phone: 44-1334-463554

Program Manager

Resource Conservation and Resiliency

SERDP and ESTCP

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