Hydrodynamics of humpbacks as a health indicator

In this study, researchers tested on humpbacks a hydrodynamic analysis method generally applied to animals with excellent diving skills such as sperm whales, northern bottlenose whales and pilot whales, which regularly dive to depths of over 200 m. Body density is an indirect indicator of their fat reserves and physical fitness. It also plays a role in the animal’s buoyancy, which in turn influences swimming behaviour and gliding performance – all of which has enabled the development of hydrodynamic analysis methods.

To complete the pedigree of each individual in the study, the research team took photos and videos of the animals they were tracking so that they could measure their waist girth to see how well the animals were eating. Fat samples were also collected and will be analyzed to examine the levels of lipids and hormones present. These three methods – gliding data, aerial photos and biopsies – will be used to assess the physical condition of animals and to cross-validate each of the approaches.

For Christian Ramp, this new method could provide more information on the health status of female humpbacks: “Between 2010 and 2016, we observed very few humpback and fin whale calves and we wonder if the females are not physically fit enough (i.e. whether they have enough fat reserves) to become pregnant or give birth.

“Being able to estimate physical fitness for single animals would dramatically increase our ability to monitor animals and populations, and, in case of ‘bad’ health, one could initiate mitigation or conservation measures. These animals feeding at the top of the food chain are ideal sentinel species for the entire ecosystem.”