First record of orca predation on franciscana dolphins (Pontoporia blainvillei) in Argentina.

PADULA ANTONELLA; JOAQUIN GANA; GISELA V. GIARDINO; CAROLINA DE LEÓN; ANDREA ELISSAMBURU; RODRÍGUEZ, DIEGO; PABLO DENUNCIO

THE LATIN AMERICAN JOURNAL OF AQUATIC MAMMALS

lajam

Año: 2022

1676-7497

The orca, or killer whale (Orcinus orca), is a cosmopolitan cetacean species that is known as a predator of a wide range of prey, including bony fishes, sharks, sea birds, sea turtles, sea otters, pinnipeds, dolphins, and whales (e.g. Jefferson et al. 1991; Visser 2005; Ford 2017; Wright et al. 2021).Previous reports of the orca diet off Argentina include sharks (Notorynchus cepedianus) (Reyes and Garcia-Borboroglu 2004), birds (Copello et al. 2021) and marine mammals such as dusky dolphins (Lagenorhynchus obscurus), and common dolphins (Delphinus delphis) (Coscarella et al. 2015), South American sea lions (Otaria flavescens) (López and López 1985, Grandi et al. 2012), southern elephant seals (Mirounga leonina) (Hoelzel 1991) and southern right whales (Eubalaena australis) (Sironi et al. 2008). However, all these records came from observational studies in Patagonia. In northern Argentina, the trophic ecology of orcas is poorly known. This may be related to the fact that historically orcas seemed to be sporadic visitors near the coast with only a few sightings per year, and that stranding events are very infrequent in this region. However, recent records of sightings suggest that there is an increasing trend in their occurrence in the area (BECMM, unpublished data). In the last few years, there were two orca mass-strandings in northern Argentina, along the Buenos Aires coast. The first event occurred on 25 August 2018, where six females stranded alive between Nueva Atlantis (36° 46’ S; 56° 41’ W) and Mar del Plata (38° 0’ S 57° 33’ W) (Figure 1); three of them died, and the other three were released. Unfortunately, it was not possible to take samples of these individuals.