An Irish Killer Whale feeding on Ocean Sunfish - first for the North Atlantic

24th Feb 2012 In October 2010, myself and Alessandro Pierini visited a stranded 5.12m female killer whale in Doohooma, Co. Mayo to take some samples. The whale had been reported to IWDG several days prior by James Kilroy (National Parks and Wildlife Service). While opening the carcase to access the stomachs, we found that the whale had been pregnant with a 2m near-term foetus.

We collected the stomach contents and brought them back to the lab in GMIT. Partially digested bones and some tough looking parasites were difficult to identify. Mark Holmes (National Museum of Ireland - Natural History) identified the parasites as a copepod called Cecrops latreilli. This parasite is 'host-specific' to the Ocean Sunfish (Mola mola). These parasites did not originate from the whale's stomach, but came from the prey which it had eaten. This was confirmed when the partially digested bones in the stomachs were eventually identified as those of a sunfish beak.

This is the first record of killer whale predation on sunfish for the North Atlantic. As sunfish appear to be easy targets to a killer whale, it begs the question just how often this occurs. Interestingly, a sunfish tagging study in waters off the UK and Ireland found sunfish undertaking unusually deep and sudden dives, possibly to avoid predators such as sharks or cetaceans.

The results were published yesterday in the peer-review journal Marine Biodiversity Records. If you wish to read the paper, please email me for a pdf (

Conor Ryan