By varying certain acoustic parameters, animals can use variants of graded vocalizations to signal a more detailed information about their internal state, motivation, or the degree of external danger . Discriminant function 1 was mainly shaped by the peak frequency within subunit 1 and the fundamental frequency at 1/3 duration of the entire call (combined in one principal component). On the other hand, the social organization and the strength of social relationships within otter groups may account for their vocal complexity, reflecting an underlying pattern of coevolution of social and vocal complexity in otters, as has been shown for primates , , canids ,  and herpestids . For more information about PLOS Subject Areas, click From left to right: growl, hah!, snort, and wavering scream. Since the giant otter vocal repertoire includes several gradations and variations of the vocalizations , we restricted our analysis to vocalizations which could readily be distinguished by structure, context, or a combination of both. Giant otters adopt communal latrines beside campsites, and dig dens with a handful of entrances, typically under root systems or fallen trees. Besides the plasticity in group composition in giant otters, the basic family group of a breeding pair with offspring of several years likely promotes long-term individual relationships and diversity of social roles in giant and Asian small-clawed otters. North American river otters, Lontra canadensis, showing a variable social structure and cooperative foraging , , emit 11 distinct vocalization types (four distinct vocalizations with seven subtypes) . The oscillograms show pressure changes over time. The giant otter is an especially noisy animal, with a complex repertoire of vocalizations. With the characteristic vocalizations of giant otters, this male made clear who dominated the submerged realm of the Pantanal. It might function as a warning of group members against intruders or humans. At sec 12, the mother approaches him, climbs the trunk (sec 19) and begs for the fish (begging calls and a begging scream gradation from sec 20). Subadult giant otters may stay as helpers within the family or leave their natal territory when reaching sexual maturity , , .  https://doi.org/10.1371/journal.pone.0112562.s011. We found a vocal repertoire with 22 distinct vocalization types produced by adults and 11 vocalization types within the babbling bouts of the neonates. Hums and coos are more reassuring within the group. Like meerkat pups, giant otter cubs are mobile and benefit from food provision by adults, from signalling their spatial location and from ‘outcalling’ their siblings. It may also be included in begging bouts or emitted during play. The giant otter ranges across north-central South America; it … This rarely emitted vocalization is tonal with two modulations. The survival of the giant otter populations in the Guianas is essential to the survival of this endangered species in South America. The hum gradation, like hum and contact call alone, was produced in the context of group cohesion. The structure and frequency modulation is very similar to that of isolation calls. Females appear to give birth year round, although in the wild, births may peak during the dry season. From left to right: mating call and suckling call. We suggest that the cubs need to practice the shift from the constant frequency part to the modulated frequency and back. The babbling bouts of neonate giant otter cubs very likely fulfil the two main purposes of vocal practise and social care solicitation , , . The sisters were left with expressions that seemed a mixture of surprise and curiosity. Yes Other countries have taken a lead in designating protected areas in South America. Consistent with the recent knowledge on otter sociality and acoustic communication, we like to emphasize that giant otters still belong to the socially most complex species and that their social complexity is reflected in their sophisticated vocal system. The IUCN listed the giant otter as "endangered" in 1999; it had been considered "vulnerable" under all previous listings from 1982 when sufficient data had first become available. Giant otter cubs may switch from babbling to begging vocalizations and isolation calls as care eliciting cues during development. Generally, only cubs and juveniles emit the suckling call while nursing, but in the Tierpark Hagenbeck group, we recorded suckling calls of subadults nursing after the death of a new born litter. Gymnotids, such as the electric eel, and the large silurid catfish are among aquatic competitors. As long as they are depended on food sharing from elder group members, they engage in intense begging for food . The vocalizations emitted in the context of begging behaviour included the ascending scream, the begging call, begging scream and begging scream gradation, and the whine. It is the noisiest otter species, and distinct vocalizations have been documented that indicate alarm, aggression, and reassurance. Wild giant otters were fed an amount of 2.0 to 6.0 kg of fish ( trout, whiting and )! Plos Subject areas, clearing the vegetation along riverbanks thinly distributed population remnants 35 ] it can close ears! Sometimes emitted during play approach human beings Duplaix identified 9 distinct sounds, with an record... A more sophisticated vocal repertoire [ 47 ] they are extremely cohesive cooperative. Generally normal or slightly myopic, both on land use and human intrusion required. 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