Piotto M, Barberá I, Sironi M, Rowntree VJ, Uhart MM, Agrelo M, Fernández Ajó AA, Seger J, Marón CF

Seabird attacks contribute to calf mortality in a whale population

Southern right whales Eubalaena australis off Península Valdés (Argentina) faced unprecedented calf mortality between 2003 and 2013, setting a record for the species. Notably, this population has also been known for experiencing long-term kelp gull Larus dominicanus micropredation. Piotto and co-authors analysed a 25-year dataset of gull attacks and calf mortality, demonstrating that attacks doubled the probability of calves dying. The harassment likely contributed to late-season deaths of older calves, as repeated attacks may degrade calf health over the calving season. The results also suggested that death rates could be influenced by other unidentified factors. These findings raise concerns for other marine mammal populations now experiencing seabird attacks, since long-term micropredation could challenge their conservation.

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