Individuality in South American sea lion (Otaria flavescens) mother–pup vocalizations: Implications of ecological constraints and geographical variations?

Abstract

a b s t r a c t Frequent mother-pup separations and reunions occurring in the South American sea lion Otaria flavescens require a well-developed individual recognition system. Individuality in mothers' and pups' calls of this species has been found in Península Valdés (PV), Argentina (with individuality rates of 95% and 89%, respectively). In order to test the hypotheses of ecological constraints (i.e., population density, habitat) and geographic variation affecting the characteristics and/or the individuality of vocalizations, we studied another population at Isla de Lobos (IL), Uruguay, separated by approx. 1200 km from PV. DFAs showed classification rates of 63.2% in mothers and 53.3% in pups. This lower degree of individuality can be explained by differences in population density. Differences in acoustic characteristics were also found: at IL mother and pup calls tended to be shorter in duration and mother calls lower-pitched. This can be explained by an adaptation to the local environment: at IL sea lions breed in sympatry with South American fur seals in an obstructed habitat whereas PV sea lions are the unique species in the colony constituted by an open habitat. Finally, the acoustic differences can also be a consequence of the genetic isolation that has been found between these two colonies of O. flavescens.

Pectoral fin contact as a mechanism for social bonding among dolphins

“…Bruck (2013) confirmed that dolphins are capable of long-term social memory spanning decades, and other researchers have found via numerous studies that bottlenose dolphins readily recognize and react to playbacks of the signature whistles of familiar, even related, individuals (e.g., Janik, Sayigh, & Wells, 2006;King, Harley, & Janik, 2014;Sayigh, Esch, Wells, & Janik, 2007). For many species, kin recognition has been documented for aquatic mammals between mother and offspring, siblings, and second-generation relations via visual, vocal and olfactory cues (e.g., Sauvé, Beauplet, Hammill, & Charrier, 2015;Trimble & Charrier, 2011;Wilson et al, 2015), non-kin require social mechanisms or tools to establish and maintain a social relationship with a new conspecific.…”

Individual signatures in the vocal repertoire of the endangered Mediterranean monk seal: new perspectives for population monitoring

“…However, a less complex task aiming to classify individuals using their vocalizations can be done by performing acoustic statistical analyses without testing animals. Such 'passive' individual classifications have been performed on many pinnipeds, with both aerial and underwater calls of mother−pup pairs and males (Insley et al 2003, Collins et al 2005, Charrier & Harcourt 2006, Khan et al 2006, Van Parijs & Clark 2006, Risch et al 2007, Gwilliam et al 2008, Van Opzeeland et al 2009, Charrier et al 2010, Trimble & Charrier 2011, Sauvé et al 2015.…”

Behavior and body mass changes of a mother and calf Pacific walrus (Odobenus rosmarus divergens) during the suckling period

“…Walruses often live in herds, and therefore calves and mothers have to find and identify each other before suckling begins [Charrier et al, ]. In the wild, South American sea lions ( Otaria flavescens ) are known to use olfactory cues at close quarters (nuzzling) as a final check of pup identity [Trimble and Charrier, ]. Due to the difficulty of observing these behaviors on crowded walrus haul‐outs, information about whether or not vocalizations or nuzzling by walrus calves occur in the wild is unavailable [Gehnrich, ].…”