George Sato

Project Title: Biomechanical analyses to enable at-sea monitoring of eco-physiological traits of diving mammals

Lipid stores are used as an indicator of the health of phocid seals since it is used as an energy reserve. Given that lipids are less dense than other body tissues, the quantity of lipid stores carried by a diver changes its net buoyancy underwater. Methods that looked at the changes in buoyancy during ascent and descent glides successfully derived the body density of deep-diving animals. However, estimating the lipid content of shallow-diving animals poses a challenge; the method cannot distinguish the buoyancy from air trapped in the respiratory tract and the lipid stores at shallow depths.

Air-breathing animals stroke strongly at shallow depths to overcome the buoyancy force generated by gas, which suggests that the stroking period is a key indicator of gas volume. My research aims to analyze the stroking periods to develop a method to estimate the body density of shallow-diving phocid seals as a quantitative index of their health. The results from this project will help identify areas where the seals gain their fat and where anthropogenic stressors may coincide with their critical habitats. This information would be important for policymakers and offshore industries to assess the impacts on marine mammals within these areas.