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My study area, biomechanics and bioenergetics of diving marine mammals, lies at the intersection of a number of fields within biology as well as incorporating ideas from engineering and physics. I have developed several methods to study the fine-scale biomechanics and energetics of marine mammals using multi-sensor tags. However, these methods have broad application to understanding gaits, locomotion and energetics of many marine and terrestrial taxa. My interest in understanding how animals overcome and exploit forces to move efficiently led me to study the biomechanical strategies of cetacean locomotion. I believe that it is by combining biomechanical and physiological avenues of research that will lead to a better understanding of animal locomotion capabilities.
During my PhD:
- I developed a simple and robust method that allows for more accurate studies of the fine scale kinematics and energetics of swimming animals. This method combines magnetometer and accelerometer on-animal sensor data gathered with DTAGS to identify and separate orientation and thrust force. I validated this method with a gyroscope sensor showing that magnetometers offer a low-power alternative than gyroscopes for miniature tags - thus enabling longer term deployments.
- I applied this method to study in detail the biomechanics of beaked whales which perform foraging dives up to 1500 m deep and last 1-2 h. I discovered that the production of a fast gait at the end of long dives may involve the recruitment of fast-twitch fibers, prolonging foraging time at depth, when oxygen stores are nearing exhaustion. This has strong implications for our interpretation of why these species are so sensitive to sound, and may even strand due to their response.
- I also developed a new and robust technique to estimate animal energy expenditure independently of the animal’s body size and account for changes in speed, for the first time, allowing cross-species and cross-behaviours comparisons. Using a DTAG data set from 11 free-ranging cetacean species covering a 3000:1 mass range, I provided the first existent empirical support for the theoretical prediction that mass-specific force production decreases with increasing body mass as mass-1/3.
- I developed a hydrodynamic model that allows the estimation of relative diving lung volume. By applying this method I show that beaked whales adjust their diving lung volume by inhaling less air during shorter-shallower dives than during deep-long dives. This method could be used to identify whether or not beaked whales change their intended dive depth (e.g., switch from a shallow to a deep dive) due to anthropogenic sound exposures.
(source: symbiosis database)