Cephalopod prey of light-mantled sooty albatross Phoebetria palpebrata, resource partitioning amongst Kerguelen albatrosses, and teuthofauna of the southern Indian Ocean

The cephalopod diet of the light-mantled sooty albatross Phoebetria palpebrata was determined for the first time at the subantarctic Kerguelen Islands by sorting similar to 7000 accumulated beaks from 66 regurgitated boluses. Twentytwo taxa were identified, including four dominant squid species that are all endemic to the Southern Ocean: Galiteuthis glacialis (49.8% of the lower beaks) Psychroteuthis glacialis (18.5%), Martialia hyadesi (16.2%) and Moroteuthopsis longimana (6.9%). Beak delta C-13 values indicated that all adult P. glacialis, almost all juvenile M. longimana, and most adult G. glacialis were caught in Antarctic waters, while albatrosses preyed upon juvenile M. hyadesi in subantarctic waters. Comparative analysis of lower beaks accumulated in food samples of Kerguelen albatrosses showed that the four main sympatric albatross species segregate primarily by species-specific foraging grounds. Light-mantled sooty albatross feed on the Antarctic P. glacialis, wandering albatross Diomedea exulans on subantarctic and subtropical histioteuthids (41.4%), and grey-headed albatross Thalassarche chrysostoma and black-browed albatross T. melanophris on subantarctic ommastrephids (69.3% and 65.7%, respectively), with black-browed albatross also preying upon neritic endemic octopuses (17.6%). Cephalopod prey of Kerguelen albatrosses highlight the abundance and importance of some squids in the functioning of the pelagic ecosystem of the southern Indian Ocean, such as ommastrephids, M. longimana, P. glacialis, Histioteuthis atlantica, H. eltaninae, and G. glacialis. Based on the diet of the light-mantled sooty albatross, P. glacialis appears common in high-Antarctic waters of the southern Indian Ocean, whereas the poorly known Psychroteuthis sp. B (Imber) is evidently present in Antarctic waters south of the Kerguelen Islands.

Automated summary

The diet of the light-mantled sooty albatross Phoebetria palpebrata was studied for the first time at the Kerguelen Islands in the subantarctic region by analyzing the beaks from regurgitated boluses. The study identified 22 taxa, including four dominant squid species endemic to the Southern Ocean. The results showed that different albatross species have species-specific foraging grounds, and the cephalopod prey of Kerguelen albatrosses highlighted the abundance and importance of certain squid species in the pelagic ecosystem of the southern Indian Ocean.