Mariano Alberto Coscarella

The instantaneous diet of South American sea lions ( Otaria byronia ) and South American fur seals ( Arctocephalus australis ) was analyzed using scats collected from shared haul‐out islands in the northern region of San Jorge Gulf, Patagonia, Argentina. Prey species were identified using otoliths, squid beaks, and crustacean exoskeletons during a long‐term project from 1999 to 2024. Sea lions and fur seals share several prey species, as well as with the fishing fleet, since most of them are commercial species. The diet of fur seals was predominantly pelagic, with Argentine anchovy ( Engraulis anchoita ) as a key prey, whereas sea lions showed a more demersal feeding pattern, with Argentine hake ( Merluccius hubbsi ) as the main fish prey. Argentine shortfin squid was also a major dietary component in both species, particularly during the early years of the study, when it dominated several sampling periods. Over time, both species exhibited a consistent shift in diet composition, characterized by a decrease in fish and cephalopods and an increasing contribution of crustaceans. The changes observed over the 26‐year period generally include a decrease in fish and an increase in crustaceans in the diet of both pinnipeds. The most important crustaceans were Argentine red shrimp and squat lobster, although their relative contribution differed between species. These changes, observed over a multi‐decadal period, are consistent with a broader reorganization of the Patagonian marine ecosystem. The observed patterns likely reflect changes in prey availability associated with sustained fishing pressure, including the extraction of key fish stocks and the input of fishery discards, acting in combination with environmental variability. Overall, our results support the use of pinnipeds as sentinel species for detecting long‐term trophic changes, as their diet integrates ecosystem‐level responses across multiple trophic levels.

We describe an air–water interface calling behavior observed in southern right whales (SRWs; Eubalaena australis) in Golfo Nuevo, Península Valdés, Argentina. This behavior involves SRWs producing audible vocalizations at the surface, here termed “interface vocalizations” (IFVs), which propagate simultaneously in-air and underwater. IFVs were documented through opportunistic visual observations combined with synchronized in-air and underwater recordings, complemented by citizen science videos. Twenty IFVs were recorded across eight events, with ten including fully synchronized acoustic data. Both in-air and underwater components are tonal, low-frequency signals with different harmonic structures and variable duration, perceived in air as “foghorn”-like sounds. Behavioral and acoustic analysis indicates that IFVs are intentionally produced, voluntarily controlled, non-breathing-related vocalizations. All callers were adult whales observed across simple and complex social contexts. The findings support IFVs as a distinct sound category from those previously described for SRW, with anatomical production likely mediated by the laryngeal apparatus. These results highlight the plasticity of SRW acoustic behavior and the complexity of its sound production, raising questions about the potential biological, communicative, and adaptive roles of IFVs in dual-pathway signaling.

We report the first video-documented case of orca ( Orcinus orca ) cooperative prey-handling and feeding behavior on a southern right whale (SRW, Eubalaena australis ) calf carcass, along with harassment events and whale responses, recorded in the Natural Protected Area El Doradillo in Península Valdés, Argentina. Drone footage and shore-based observations were conducted on September 5, 2025, revealing an orca group refloating and feeding on a sunken whale calf carcass. The orca group consisted of six identified individuals from the Península Valdés population. Drone footage (total recording time: 1 h 37 min) showed coordinated behavior among orcas, who alternated in holding, lifting, and releasing the carcass, suggesting cooperative handling. The orcas engaged in forty-six harassment events targeting southern right whales, especially mother–calf pairs. Defensive responses described as 360° turns and zigzag pattern were elicited more often when orcas approached from the latero-caudal angle with respect to SRW head. These results expand the knowledge on the behavioral ecology of this orca population and underscore the ecological significance of orca–right whale interactions in one of the most important SRW breeding grounds in the Southwestern Atlantic Ocean.

Los playeros rojizos son aves playeras migradoras de larga distancia, que vuelan desde el Ártico hasta el sur de Sudamérica. Realizan paradas migratorias en escasos sitios con elevada oferta trófica, los cuales actúan como cuellos de botella poblacionales. Se han registrado consecuencias catastróficas a nivel poblacional cuando los recursos no estuvieron disponibles durante una parada migratoria, por lo que dichos sitios deben ser manejados y conservados. En su migración al norte, entre los meses de marzo–mayo se detienen en Península Valdés (Patagonia Argentina), donde se realizaron monitoreos todos los años entre 2006–2013. La península está rodeada por 2 golfos donde las playas Blancas, Fracasso, Conos y Sarmiento fueron monitoreadas en el Golfo San José y playa Colombo en el golfo Nuevo. Se tomaron datos de encuentro-reencuentro de playeros rojizos anillados individualmente en todas las playas utilizando telescopios. Para evaluar la fidelidad al sitio por parte de los playeros rojizos, se utilizó el Índice Estandarizado de Fidelidad al Sitio. Este índice se calculó para cada playa y agrupando las playas según el golfo donde se ubican. En orden decreciente, los playeros rojizos fueron más fieles a las playas de Blancas, Fracasso y Colombo. Cuando las playas se agruparon por golfo, la fidelidad al sitio fue mayor en el golfo San José que en el golfo Nuevo, la cual puede estar relacionada con la reportada mayor oferta trófica en este golfo. La aplicación de este índice es una herramienta útil y poderosa para tomar decisiones o proponer estrategias para su manejo. Palabras clave: aves playeras, conservación, encuentro y reencuentro, escala migratoria, manejo.