Cephalopods in marine predator diet assessments: why identifying upper and lower beaks is important

• Published in: ICES Journal of Marine Science
• Main Authors: Xavier, José C., Phillips, Richard A., Cherel, Yves
• Other Authors: Institut Marine Research, University of Coimbra Portugal (UC), British Antarctic Survey (BAS), Natural Environment Research Council (NERC), Centre d'Études Biologiques de Chizé (CEBC), Institut National de la Recherche Agronomique (INRA)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: cephalopod beaks; marine ecosystems; top predator diets; trophic interactions; [SDE]Environmental Sciences; Diomedea exulans; Wandering Albatross
• Online Access: https://hal.science/hal-00623770; https://doi.org/10.1093/icesjms/fsr103

International audience Cephalopods are components of the diet of many predators worldwide. They are identified mainly using their chitinized upper and lower beaks, but because it has been assumed that the number of upper and lower beaks would be the same in predator diet samples, more effort has been put into creating keys for the lower beaks, which are more easily identifiable from morphology. A test is made of whether the number of upper and lower beaks differs in diet samples collected from a major cephalopod predator, the wandering albatross (Diomedea exulans), potential biases in the estimation of predator diets are assessed, and upper: lower beak ratios in published studies of other seabirds, seals, whales, and fish from different parts of the world reviewed. The ratio of upper to lower beaks in diet samples from wandering albatrosses varied greatly in a single year (from 69.6% more lower beaks to 59% more upper beaks), and between years (from 0.5 to 32.1% more upper beaks), and biases were greater for certain cephalopod species, resulting in underestimation of their relative importance. Future studies need to consider using both upper and lower beaks to improve the assessment of the contribution of different cephalopods to predator diets.