MARSHALL, C.D.; KOVACS, K.M.; LYDERSEN, C.; Texas A&M University at Galveston; Norwegian Polar Institute; Norwegian Polar Institute: Behavioral Performance of Feeding in Bearded Seals (Erignathus barbatus)

Bearded seals are arctic phocids that feed predominantly on benthic prey. Walruses, well-known benthic feeders, exhibit specialized behaviors such as suction and hydraulic jetting. To understand the feeding capabilities of bearded seals we conducted feeding experiments with captive seals to assess the relative importance of biting vs. suction. Feeding trials were conducted both in and out of water using a feeding station that incorporated a 45-degree mirror. The mirror allowed simultaneous frontal and lateral views during feeding events. Food items were presented to seals by projecting food through holes in a plexiglass sheet and within cylinders recessed behind the plexiglass. Food projecting from holes could be ingested either by biting or suction, whereas food within recessed cylinders could only be ingested by suction. Biting was determined by visible use of teeth and increased gape angle. Suction was determined by the turbulent flow of water, or food color, through holes in the back of the cylinders. Feeding events were videotaped at 60 fields/s. Footage was analyzed in real-time and frame-by-frame to determine the method of feeding utilized. Seals ingested food using both biting and suction. However, biting was observed only during out-of-water feeding trials. Suction feeding dominated underwater trials, even when food was accessible by biting. When food within cylinders was difficult to remove, seals alternated hydraulic jetting with suction to extract food. This was demonstrated by repeated reversals of turbulent water flow through the recessed cylinders. Muscular lips were pursed to create a pipette-like aperture to facilitate forceful water flow in and out of the mouth. This is the first account of hydraulic jetting use by bearded seals.