Kinematics and energetics of foraging behavior in Rice's whales of the Gulf of Mexico

The endangered Rice's whale (Balaenoptera ricei) is endemic to the Gulf of Mexico (GOM) and has a small population of fewer than 100 individuals. Little is known about their foraging ecology. Suction cup tags were attached to two Rice's whales to collect information on their diving kinematics and foraging behavior. The tagged whales primarily exhibited lunge-feeding near the sea bottom and to a lesser extent in the water column and at the sea surface. During foraging dives, the whales typically circled the prey before executing one or two feeding lunges. Longer duration dives and dives with more feeding lunges were followed by an increase in the breathing rate. The average lunge rate of both animals was much lower than expected based on comparative research on other lunge-feeding baleen whales, which may be related to differences in prey or inter-specific differences, or may be an indication of different foraging conditions. Overall, these data show that Rice's whale foraging behavior differs from other lunge-feeding rorqual species and may be a significant factor in shaping our understanding of their foraging ecology. Efforts to mitigate threats to the Rice's whale will benefit from improved understanding of patterns in habitat use and fine-scale ecology within the population.