Animal-borne video tags have been successfully used to observe the feeding behavior of free-ranging animals. While previous use of these data has focused on the tagged animal, this study examines observations of intra and inter-specific interactions that provide insights into the roles of competition and coordination in the foraging efficiency of top predators. Humpback whales are often associated with other species during feeding and sometimes form feeding aggregations in response to dense prey. While they are known to engage in coordinated foraging, less is known about competition within these aggregations. As part of a larger project looking at humpback feeding behavior, we examined data from multi-sensor video tags where whales were feeding in aggregations along with other species. Preliminary results from the analysis of 5.5 hrs of video of a fish-feeding individual in 2015 showed foraging interactions between the tagged animal, conspecifics and other sympatric predators. Using front and rear facing cameras as well as a 3 dimensional reconstruction of animal movement derived from accelerometry, we were able to identify multiple instances of collision-avoidance in the pursuit of prey, indicating competition. Over the course of 17 visible feeding bouts there were 8 aborted or obstructed lunges and 3 instances of contact between the tagged animal and a conspecific. At other times, the tagged animal lunged in synchrony with conspecifics, which may indicate coordinated foraging. Additionally, we observed sympatric predators including sea lions, cormorants, alcids and shearwaters foraging in synchrony with humpbacks on the same resource. These data allow successful rorqual lunge-feeding events to be discriminated from unsuccessful events by combining video and 3D movement sensors, and provide insight into the complex interactions that occur during foraging, including competition and coordination with conspecifics as well as sympatric commensalism.
Citation:
Fahlbusch, J., D. Cade, J. Goldbogen, A. Friedlaender, A. Stimpert, J. Calambokdis. 2017. Intra and inter-species interactions among humpback whales in Monterey Bay: Competition and not just cooperation. Abstract (Proceedings) 22nd Biennial on the Biology of Marine Mammals, Halifax, Nova Scotia, October 22-27, 2017.