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 preexisting 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 (n = 2680) and stranding photographs of dead calves (n = 192) 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. In the 1980s and 1990s, mothers and calves had roughly equal numbers of lesions (one to five), but by the 2000s, calves had more lesions (nine or more) covering a greater area of their backs compared to their mothers. Living mother-calf pairs and dead calves in Golfo Nuevo had more lesions than those in Golfo San José in the 2000s. The number and area of lesions increased with calf age during the calving season. Intensified Kelp Gull harassment at Península Valdés could be compromising calf health and thereby contributing to the high average rate of calf mortality observed in recent years, but it cannot explain the large year-to-year variance in calf deaths since 2000.

). Postmortem examination and pathogen testing were performed on 212 whales; 208 (98.1%) were calvesof-the-year and 48.0% of these were newborns or neonates. A known or probable cause of death was established in only a small number (6.6%) of cases. These included ship strike in a juvenile and blunt trauma or lacerations (n = 5), pneumonia (n = 4), myocarditis (n = 2), meningitis (n = 1), or myocarditis and meningitis (n = 1) in calves. Ante-mortem gull parasitism was the most common gross finding. It was associated with systemic disease in a single 1−2 mo old calf. Immunohistochemical labeling for canine distemper virus, Toxoplasma gondii and Brucella spp., and PCR for cetacean morbillivirus (CeMV), influenza A, and apicomplexan protozoa were negative on formalin-fixed, paraffinembedded lung and brain samples from a subset of whales; PCR for Brucella spp. was positive in a newborn/neonate with pneumonia. Skin samples from whales with gull parasitism were PCR negative for CeMV, poxvirus, and papillomavirus. This is the first long-term study to investigate and summarize notable post-mortem findings in the PV SRW population. Consistent, significant findings within or between years to explain the majority of deaths and those in high-mortality years remain to be identified.

The amount of energy an animal uses to move may constitute a significant fraction of its energy budget, so detailed descriptions of wild animal activity budgets can help to understand the ecology of a species, both at the individual and at the population levels. The rocky-reef fishes inhabiting the northern Patagonian gulfs of Argentina are important economic and recreational resources for which no activity or energy budgets are available. This fish assemblage may reach high aggregated biomasses (exceeding several hundreds of kilogrammes of fish distributed along a few hundred metres of linear reef ledges) and is not clear how such biomasses can be supported by the low productivity of the Patagonian coastal waters. We used animal-attached accelerometers to characterise the behaviours and activity budgets for the most abundant and ubiquitous species of this assemblage, the Argentine sea bass or 'Mero' Acanthistius patachonicus (Jenyns, 1840; Osteichthyes: Serranidae). Sixteen individuals were tagged (two in captivity and 14 free-living) and an ethogram was generated from acceleration recordings in varying environmental conditions. Two algorithms were used to classify the behaviours of wild fish. Both showed generally similar results during the cold-water season (8-10°C), but differed slightly in the warm-water season (16-18°C). Overall, sea bass were more active during warm season (mean time spent engaged in active behaviours; 46%, range; 24-60%). In contrast, during cold season fish only spent a mean of 29% of their time in active behaviours (range; 15-49%). No clear response to tidal state or ambient light was found, but some fish were more active during the night in the cold water season. Here, we provide the first activity budgets for the conspicuous Argentine sea bass, which contribute to our understanding of rocky-reef fish behaviour in Patagonia.Abstract in French is available with online material.

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Marine mammals rely on blubber mainly for energy storage, buoyancy, and streamlining. Mysticetes are born with a relatively thin fat layer that grows rapidly during nursing. However, little information on blubber deposition patterns is available for baleen whale calves. We measured blubber thickness at nine body locations in 350 southern right whale (Eubalaena australis) newborn to 4–6‐month‐old calves that died on the Península Valdés (Argentina) calving ground from 2003 to 2019, to document changes in blubber thickness with growth. Additionally, we looked for differences in blubber thickness and lipid content of the outer/superficial blubber in calves that died in years with high (2003, 2005, 2007–2013) and low calf mortality (2004, 2006, 2014–2019) to test whether the former were suffering from gross nutritional stress. Blubber thickness increased at all body locations with calf length. Along the cranio‐caudal axis, blubber increased in the dorsal and ventral planes, but decreased laterally towards the peduncle, possibly to improve streamlining. We found no difference in blubber thickness and lipid content between high and low mortality years, suggesting that individuals were not undernourished. This is the first study to describe progressive increases in calf blubber during growth and contributes knowledge to right whale health and ontogeny.