Sentence:  Although few observations have been made of feeding <WSD>crabeaters</WSD>, it is assumed that they take bites from a swarm of krill, extracting one or two. <WSD>Crabeaters</WSD> sometimes feed collectively, which may increase the efficiency of their hunt. 
Meaning of the word marked with <WSD> tags:  An Antarctic seal ("Lobodon carcinophagus") that feeds on krill.