Southern elephant seal vagrants in Ecuador: a symptom of La Ni\xf1a events?

Diego Páez-Rosas,Juan José Alava,Juan De Dios Morales,Marjorie Riofrío-Lazo,Jorge Ortega,Raúl Carvajal

doi:10.1186/s41200-018-0149-y

Abstract

BackgroundExtralimital observations of pinnipeds are important to understand the effects of changing climates on our oceans and the distribution of these species. The southern elephant seal (Mirounga leonina) is a known vagrant species that moves over long distances. We report three new records of M. leonina in interior freshwater tributaries of the Guayas River Estuary Basin (Gulf of Guayaquil) and northern coast of Ecuador between October 2017 and January 2018 during a cold episode of La Nina event in the southeastern Pacific.ResultsThe elephant seals were identified according to their large size (~ 5 m for adult and 2–3 m for juveniles/subadults), the head to neck size ratio, and the size and external morphology of the proboscis, which was used as a key trait to differentiate M. leonina from the Northern elephant seal (M. angustirostris). The observations of M. leonina in Ecuador highlight an extreme movement covering an assumed total distance of approximately 8000 km from the circumpolar region. The cold event “La Niña” with sea surface temperature anomalies ranging − 1.5 °C to − 0.5 °C in October 2017 likely triggered the extralimital movements of these animals.ConclusionRecurring observations of M. leonina in the Guayaquil Gulf suggest the importance of this highly productive region and tropical estuarine-riverine habitats as temporary haulout sites for resting. These new findings indicate that vagrant individuals influenced by oceanographic events and eco-physiological processes are reaching this region more frequently than previously thought.

Highlights

Extralimital observations of pinnipeds are important to understand the effects of changing climates on our oceans and the distribution of these species
The South Georgia population group is comprised of the populations existing on the South American continent, including the Valdés Peninsula and Malvinas Islands (Slade et al 1998; Hoelzel et al 2001), as well as a small colony located in Ainsworth Bay, Magallanes Region (i.e. XII Region of Magallanes) and Chilean Antarctica (Vargas 2012)
We report apparently healthy M. leonina in the Guayas River Basin (Gulf of Guayaquil) and on Ecuador’s north coast, and discuss the possible influence of La Niña event as a driving atmospheric-oceanographic force affecting the distribution and behavioral patterns of the species

Summary

Introduction

Extralimital observations of pinnipeds are important to understand the effects of changing climates on our oceans and the distribution of these species. The southern elephant seal (Mirounga leonina) is a known vagrant species that moves over long distances. The southern elephant seal (Mirounga leonina) is the largest pinniped in the world and is not habitually found in tropical areas because of its circumpolar and sub-Antarctic distribution in the southern ocean (Le Boeuf and Laws 1994; Jefferson et al 2015). Adult southern elephant seals present a marked sexual dimorphism due to their polygynous system (Le Boeuf 1974; Baldi et al 1996). This species is widely distributed in the circumpolar and sub-Antarctic islands, where it is assembled in three population groups: South Georgia, Kerguelen and Macquarie (Deméré et al 2003; McMahon et al 2005). As well as winter haulouts of southern elephant seals are found at Marion Islands, South Africa (Kirkman et al 2001; Kirkman et al 2003; Kirkman et al 2004)

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