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

Macarena Agrelo*, Carina F. Marón, Fábio G. Daura-Jorge, Victoria J. Rowntree, Mariano Sironi, Philip S. Hammond, Simon N. Ingram, Florencia O. Vilches, Jon Seger, Paulo C. Simões-Lopes

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

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Abstract

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.
Original languageEnglish
Article number20230119
Number of pages7
JournalBiology Letters
Volume19
Issue number6
Early online date7 Jun 2023
DOIs
Publication statusPublished - 7 Jun 2023

Keywords

  • Eubalaena australis
  • Gull-inflicted lesions
  • Mortality
  • Population dynamics

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