The innovation and diffusion of trap-feeding, a novel humpback whale foraging strategy

The innovation and diffusion of novel foraging strategies within a population can increase the capacity of individuals to respond to shifts in prey abundance and distribution. Since 2011, some humpback whales (Megaptera novaeangliae) off northeastern Vancouver Island (NEVI), Canada, have been documented using a new feeding strategy called trap-feeding. We provide the first description of this foraging innovation and explore the ecological and social variables associated with its diffusion using sightings data, video analysis, and logistic regression modeling. The number of humpback whales confirmed to trap-feed off NEVI increased from two in 2011 to 16 in 2015. Neither the locations of trap-feeding sessions nor prey species consumed differed from those documented during lunge-feeding. However, preliminary results indicate that the schools of fish consumed when individuals trap-fed were smaller and more diffuse than those consumed when whales lunge-fed. Top-ranked models predicting whether an individual would be observed exhibiting trap-feeding behavior included the following parameters: average number of days per year that the individual was seen off NEVI and proportion of the individual's associations that were with other trap-feeders. These results suggest that trap-feeding may be a culturally transmitted foraging innovation that provides an energetically efficient method of feeding on small, diffuse prey patches.