At
least 626 southern right whale (Eubalaena
australis) calves died at the Península Valdés calving ground, Argentina,
between 2003 and 2014. Intense gull harassment may have contributed to these deaths.
In
the 1970s, Kelp Gulls (Larus dominicanus)
began feeding on skin and blubber pecked from the backs of living right whales
at Valdés. The frequency of gull attacks has increased dramatically over the
last three decades and mother-calf pairs are the primary targets.
Pairs
attacked by gulls spend less time nursing, resting and playing than pairs not
under attack. In successive attacks, gulls open new lesions on the whales’
backs or enlarge pre-existing ones. Increased wounding could potentially lead to
dehydration, impaired thermoregulation, and energy loss to wound healing.
The
presence, number and total area of gull-inflicted lesions were assessed using
aerial survey photographs of living mother-calf pairs in 1974–2011 and
stranding photographs of dead calves in 2003–2011. The percentage of living
mothers and calves with gull lesions increased from an average of 2% in the
1970s to 99% in the 2000s.
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