Note on the first modern record of a southern elephant seal (Mirounga leonina Linnaeus, 1758) in Los Ríos Region, southern Chile

Abstract

2017). In the southeastern Pacific, intra-annual shifts in food resource availability related to coastal upwelling cycles, and the occurrence of La Niña phenomena have been discussed as possible explanations for the repeated appearance of individuals farther north in Chile (Sepúlveda et al., 2007; Pacheco et al., 2011), Ecuador (Páez-Rosas et al., 2018), Colombia (Ávila et al., 2021), and Panama (Redwood & Félix, 2018). Like in southern Chile (Acevedo et al., 2019; Cárcamo et al., 2019), increasing numbers of anecdotal southern elephant seal sightings in the Eastern Tropical Pacific have been recently hypothesized to result from two causes that would hence outweigh ENSO (El Niño-Southern Oscillation) cycling as sole possible contributor: 1) a possible density-dependent extralimital growth of the three Atlantic populations, and 2) global climate change-related largescale regime shifts in the Southern Ocean (Alava et al., 2022). An observed prevalence of often immature or subadult males in all of these northerly anecdotal sighting reports – at their time often considered to be linked to vagrancy (Páez-Rosas et al., 2018) – has been attributed to sex-based differences in southern elephant seal foraging behavior/dietary niches and to age-dependent experience in the selection of haul-out sites (Mulaudzi et al., 2008; Acevedo et al., 2016; Sepúlveda et al., 2018). On a global scale, extra-distributional coastal sightings include male adults in the southeastern Atlantic (Bester et al., 2022) and, among others, infants in the southwestern Atlantic (Siciliano et al., 2020), encouraging comparative studies concerning (re-)colonization and range extension processes. As research on the ecology and behavior of southern elephant seals in their re-colonized historic southeastern Pacific range is only beginning, detailed observations of single sightings might help to further develop working hypotheses. Therefore, details of the first modern record of a southern elephant seal in Los Ríos Region, near 40° S in southern Chile (Fig. 1A), are described here. Cárcamo et al. (2019) had already collected census data to reassess the distribution of southern elephant seals in the southeastern Pacific. They included southern elephant seal sighting records from authorities (Servicio Nacional de Pesca y Acuicultura/Chile National Fishery and Aquaculture Service of Chile – SERNAPESCA); records from 2009 to 2016) and The distribution of southern elephant seals (Mirounga leonina Linnaeus, 1758) in the southeastern Pacific has been subject to revision in recent years (Acevedo et al., 2016, 2019; Cárcamo et al., 2019). Southern elephant seals were hunted close to extinction by humans (Hindell & Perrin, 2009; Acevedo et al., 2016, 2019). However, since the late 20th century they have been re-colonizing breeding sites in southernmost Chile’s Magallanes Region (e.g. Cáceres, 2013; Acevedo et al., 2016; Capella et al., 2017). The recent documentation of pups and a birth event at different latitudes of the southeastern Pacific coast as far north as 38°22’ S suggests that the species is extending its southeastern Pacific distribution back to its historical continental range of up to 37° S (Acevedo et al., 2019; Cárcamo et al., 2019). A fossil record from the colder than recent Pleistocene indicates that elephant seals (Mirounga sp. Gray, 1827) in the southeastern Pacific prehistorically ranged as far north as northern Chile’s Antofagasta Region (around 23° S; Valenzuela-Toro et al., 2015). Southern elephant seals are known to undertake extensive travels of up to several thousand kilometers and to show site fidelity to foraging regions as well as to breeding and molting haul-out sites (e.g., Campagna et al., 1999; Bradshaw et al., 2004; McIntyre et al.,