Effect of kelp gull harassment on southern right whale calf survival: a long-term capture–recapture analysis

• Published in: Biology Letters
• Main Authors: Agrelo, Macarena, Marón, Carina F., Daura-Jorge, Fábio G., Rowntree, Victoria J., Sironi, Mariano, Hammond, Philip S., Ingram, Simon N., Vilches, Florencia O., Seger, Jon, Simões-Lopes, Paulo C.
• Other Authors: The Coordination of Superior Level Staff Improvement, The National Council for Technological and Scientific Development, Instituto de Conservación de Ballenas, CAPES-PRINT, Ocean Alliance
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2023
• Subjects: Argentina; Southern Right Whale
• Online Access: http://dx.doi.org/10.1098/rsbl.2023.0119; https://royalsocietypublishing.org/doi/pdf/10.1098/rsbl.2023.0119; https://royalsocietypublishing.org/doi/full-xml/10.1098/rsbl.2023.0119

Kelp gulls ( Larus dominicanus ) commonly feed on the skin and blubber of surfacing southern right whales (SRW, Eubalaena australis ) in the near shore waters of Península Valdés (PV), Argentina. Mothers and especially calves respond to gull attacks by changing their swimming speeds, resting postures and overall behaviour. Gull-inflicted wounds per calf have increased markedly since the mid-1990s. Unusually high mortality of young calves occurred locally after 2003, and increasing evidence points to gull harassment as a factor contributing to the excess deaths. After leaving PV, calves undertake a long migration with their mothers to summer feeding areas; their health during this strenuous exertion is likely to affect their probabilities of first-year survival. To explore the effects of gull-inflicted wounds on calf survival, we analysed 44 capture–recapture observations between 1974 and 2017, for 597 whales photo-identified in their years of birth between 1974 and 2011. We found a marked decrease in first-year survival associated with an increase in wound severity over time. Our analysis supports recent studies indicating that gull harassment at PV may impact SRW population dynamics.