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

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 posture...

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Bibliographic Details
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.
Format: Article in Journal/Newspaper
Language:English
Published: 2023
Subjects:
Eubalaena australis
Gull-inflicted lesions
Mortality
Population dynamics
Argentina
Southern Right Whale
Online Access:https://research-portal.st-andrews.ac.uk/en/researchoutput/effect-of-kelp-gull-harassment-on-southern-right-whale-calf-survival(034d9652-134c-4637-8d75-e21a06413c9a).html
https://doi.org/10.1098/rsbl.2023.0119
https://research-repository.st-andrews.ac.uk/bitstream/10023/27849/1/Agrelo_etal_author_accepted_ms.pdf
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Summary: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.

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