 Large whales , such as mysticetes , are not usually subject to predation , but smaller whales , such as monodontids or ziphiids , are . These species are preyed on by the killer whale or orca . To subdue and kill whales , orcas continuously ram them with their heads ; this can sometimes kill bowhead whales , or severely injure them . Other times they corral the narwhals or belugas before striking . They are typically hunted by groups of 10 or fewer orcas , but they are seldom attacked by an individual . Calves are more commonly taken by orcas , but adults can be targeted as well . 
