Insights into the diet of beaked whales from the atypical mass stranding in the Canary Islands in September 2002

Stomach contents were analysed from three species of beaked whales which mass-stranded shortly after a naval exercise conducted in the Canary Islands in September 2002. Animals from such mass strandings often contains freshly ingested food in their stomachs and can provide a more reliable guide to feeding habits than other strandings. Food remain recovered from seven Cuvier's beaked whales (Ziphius cavirostris) consisted mainly of oceanic cephalopods, the most numerous being Taonius pavo, Histioleuthis sp., Mastigoteuthis schmidti and Octopoteuthis sicula. Many of the cephalopod species found in the diet appear to undertake daily vertical migrations, being found in shallower waters during the night and moving to deeper waters during the day. Single specimens of Blainville's beaked whale (Mesoplodon densirostris) and Gervais' beaked whale (Mesoplodon europaeus) had eaten both fish and cephalopod prey. The most numerous prey remains belonged to gadid fish and viperfish (Chauliodus sp.) respectively. These results are consistent with the limited published data on diet in these species, with Mesoplodon species having a relatively higher proportion of fish in the diet whereas Ziphius specialises on cephalopods.