Research

Understanding the physiological and behavioral mechanisms and energetics that determine the ecological niche of an organism is central to my research program. As we continue to see the effects of climate change and anthropogenic stressors, this information is essential for predicting and mitigating ecosystem responses to the changing environment.

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California sea lion

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Leatherback turtle

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Humpback whale

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Emperor penguins

Current Research Projects:

Diving physiology and energetics of cetaceans (in collaboration with Drs. Peter Madsen, Mark Johnson, and Natacha Aguilar de Soto

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Cetaceans are among the largest animals ever to evolve, and as apex predators in marine ecosystems, they have a significant top-down effect on prey targeted during long, deep breath-hold dives.  It is therefore essential to understand the energetic requirements and oxygen management of cetaceans if we are to interpret and understand their role in the trophic energy cascades, their foraging ecology, limits of dive performance and ability to adapt to environmental change and disturbance.  However, very little is known about the field physiology of cetaceans due their size and hostile habitats.  At the Fjord and Bælt center (Kerteminde, Denmark) a unique opportunity exists to measure metabolic rate, heart rate, and activity in captive porpoises that live in a large net pen experiencing similar conditions to wild porpoises.  By having access to this one of a kind facility, we will be able to compare these data on captive porpoises to heart rate and activity data of wild porpoises in the same Danish waters.  This provides a unique opportunity to examine the field energetics and diving physiology of a wild cetacean.

We have recently received funding from the Office of Naval Research (ONR) to continue this line of research.  We will continue to develop the data logging technology we used on the porpoises for use on larger cetacean such as pilot whales and beaked whales.

Social behavior and site fidelity of Monterey Bay Risso’s dolphins 

Risso’s dRissoolphins are commonly observed in the Monterey Bay. Despite this, relatively little is known about the population, or about Risso’s dolphins in general (they are listed as data deficient on the IUCN red list). Drs. Birgitte McDonald and Alison Stimpert received funding from the Monterey Bay Chapter of the American Cetacean Society to conduct a study to improve our knowledge of the Monterey Bay Risso’s dolphins. Specifically we will: 1) Investigate whether the population consists of primarily resident or transient groups using photo identification and acoustic techniques. And 2) Examine the social structure of local groups by conducting focal follows of known individuals.

Diving physiology and energetics of the California sea lion (in collaboration with Dr. Paul Ponganis)

This proSeaLionTagPermitject contributes to our understanding of oxygen management and the underlying physiological mechanisms of oxygen management in marine mammals.  This information is essential if we are to interpret and understand the limits of dive performance, foraging ecology, and the ability of breath hold divers to adapt to environmental change and disturbance.  In this study we will determine the rate and magnitude of oxygen store depletion during dives, and investigate its relationship to heart rate and workload, thereby improving our understanding of oxygen management during diving, specifically the role of lung oxygen stores and oxygen delivery to tissues.

We used backpack digital recorders to measure blood oxygen depletion, heart rate, and flipper stroke rate in dives of California sea lions during maternal foraging trips to sea from San Nicolas Island.  The goals of this research are: 1) determination of the rate, pattern and magnitude of blood oxygen store depletion during both shallow and deep dives at sea, 2) documentation of heart rate profiles of shallow and deep dives, and assessment of the relationship between changes in heart rate to blood oxygen profiles, and 3) documentation of flipper stroke rate profiles during shallow and deep dives, and assessment of the relationship of stroke rate to both changes in heart rate and changes in blood oxygen profiles.  This data has been collected and Dr. McDonald is finishing up analysis.

This summer, Mason Cole will collect data on the feeding behavior and find scale diving behavior of California sea lions using accelerometers to improve our understanding of their foraging energetics.

Emperor penguin post-molt foraging behavior (In collaboration with Dr. Gerald Kooyman)

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Emperor penguins dive deeper and longer, fast longer, and endure the harshest weather conditions of all diving birds. They spend about four to five months after the breeding season deep in Antarctic pack ice, far from shore and any stations.  During this time they undergo great changes in body weight as they feed to
recover from the breeding season, lose weight while fasting during the molt, and then continue to feed before the breeding season.  Unfortunately, due to their remote location little is known about the foraging ecology and diving behavior during this critical period.  In March of 2013 we travelled deep into the Antarctic pack ice in the Eastern Ross Sea to instrument emperor penguins after they molted.  The objectives of the study were: 1) Place satellite/time depth recorder tags on 20 adult post molt birds to determine their route, rate of travel, and diving behavior as they return back to their breeding colonies, 2) Obtain an index of body condition, 3) Collect guano to determine the type of food consumed by emperor penguins in the region, 4) Conduct shipboard surveys to sight and plot the location and abundance of adult and juvenile birds on the ship’s track. We are currently finishing up analysis.  You can check out the blogs and video from the cruise here: Scripps Blog,  Tracers Blog,  National Geographic BlogTime-lapse video

Drs. Birgitte McDonald and Jerry Kooyman are excited about the findings and have submitted a proposal to continue this research.