Table 2.

Ethogram and operational definitions for prey processing methods used by phocine seals when feeding on large prey. Data were recorded as bouts of behaviour, where the animal could perform multiple prey-processing actions (e.g. multiple shakes) as part of a single bout with pauses or different behaviours in between bouts. Hence this analysis recorded the number of bouts of each behaviour that were performed, rather than how many individual processing actions were performed within each bout.

foraging behaviour	description and operational definition
gulping to swallow large prey	prey was swallowed by jerking the head backwards while simultaneously biting down on prey. This appeared to force the prey backwards into the oesophagus.
hold and tear at surface	holding and stretching prey between the teeth and forelimbs to create the tensional load that tears the prey item. This load was applied by pulling the item away from the mouth with forelimbs while simultaneously arching the head back using the neck. When performed at the surface either the head or both the head and forelimbs were positioned above the surface of the water at the start of the bout. Each bout was recorded from when the seal first holds the prey item with both its teeth and forelimbs. The bout ended if the seal dropped the prey item or if the prey item tore.
hold and tear underwater	same as hold and tear feeding at surface, but performed with both the head and forelimbs positioned underwater. This could be performed completely underwater (near the bottom of the pool) or near the surface where the animal was still facing down in the water so only their back breached the surface. Each bout was recorded from when the seal first holds the prey item with both its teeth and forelimbs, and ended if the seal dropped the prey item or if it tore.
shaking at surface	holding prey in teeth and flicking from side to side so that its own inertia causes it to tear. A bout of shake feeding commenced with the first flick and ended if the seal dropped the prey item or if the prey item broke. Hence, one bout of shaking could involve multiple shakes or flicks of the prey item.
shaking underwater	holding prey in teeth and shaking from side to side underwater. Pulling against drag in the water, rather than the inertia of the prey item, created the tensional load that caused the prey item to tear. The bout ended if the seal dropped the prey item or if the prey item tore.
securing with paw on land	prey was held against the ground on land beneath the palm of the forelimb and/or with the digits flexed so that the claws dug into the prey item. The seal then pulled away from the secured prey item by arching its neck. This applied tension as the prey item was stretched between the teeth and forelimb. A new bout was recorded when the prey was held down beneath the flipper and gripped with the teeth. The bout ended if the seal dropped the prey item or the prey item tore.