Territorial choruses of giant otter groups (Pteronura brasiliensis) encode information on group identity

Abstract

Group living animals often engage in corporate territorial defence. Territorial group vocalizations can provide information about group identity, size and composition. Neighbouring groups may use this information to avoid unfavourable direct conflicts. Giant otters are highly social and territorial animals with an elaborate vocal repertoire. They produce long-range screams when they are alert or excited, i.e. in an alarm, isolation or begging context. Long-range screams are not only produced by one individual at a time (‘single screams’) but also by multiple group members simultaneously, resulting in a highly conspicuous ‘group chorus’. Wild giant otters regularly produce group choruses during interactions with predators, when they detect intruders in their territory or before group reunions after separation. Since single screams and especially group choruses probably contribute to the groups’ corporate territorial defence, we hypothesized that group identity is encoded in single screams and group choruses. We analysed vocalizations from five wild and three captive giant otter groups and found statistical evidence for a group signature in group choruses. Results for single screams were less conclusive, which might have been caused by the comparatively lower sample size. We suggest that giant otters may gain information on group identity by listening to group choruses. Group identity likely constitutes important social information for giant otters since territory boundaries of neighbouring groups can overlap and direct inter-group conflicts are severe. Therefore, group chorusing may contribute to the mutual avoidance of members from different groups.

Conservation of Amazonian aquatic mammals

“…Pteronura brasiliensis is diurnal and very social, living in groups of up to 16 individuals that are usually formed by the dominant breeding pair and their offspring or non‐breeding subadults (Duplaix et al, 2015). Groups of P. brasiliensis actively defend their territories by scent markings (Leuchtenberger & Mourão, 2009) and vocalizations (Mumm & Knörnschild, 2017). This species builds dens, latrines and campsites along river and lake banks, which are important for sleeping, resting, breeding and territory marking.…”

“…Groups of P. brasiliensis actively defend their territories by scent markings (Leuchtenberger & Mourão, 2009) and vocalizations (Mumm & Knörnschild, 2017). This species builds dens, latrines and campsites along river and lake banks, which are important for sleeping, resting, breeding and territory marking.…”

Bats distress vocalizations carry fast amplitude modulations that could represent an acoustic correlate of roughness

“…The ability to produce screams is not unique to humans [6][7][8][9][10][11] , but, at present, we do not know whether human and non-human animals rely on similar strategies to create harsh sounding, alarm vocalizations. The word "rough" has been used in several studies to describe agonistic vocalizations of animal groups including non-human primates, otters, and birds, among others [12][13][14][15][16][17] . In those species, the acoustic correlates of roughness were not studied quantitatively using methods similar to those employed for characterizing the human soundscape.…”

Spontaneous Mouse Behavior in Presence of Dissonance and Acoustic Roughness

“…For instance, mice could have been sensitive to the slope of the ramp in each sinusoidal cycle of AM sounds ( Deneux et al, 2016 ). However, in other mammals (otters, primates or bats), studies indicate that fast AM sounds, such as a baby’s cry, are also produced in alarm calls, and/or antagonistic interactions ( Leinonen et al, 2003 ; Mumm and Knörnschild, 2017 ; Hechavarría et al, 2019 ). Since infant distress calls appear to share acoustic similarities and analogous neuronal responses across mammals ( Newman, 2007 ; Zuberbühler, 2009 ; Lingle et al, 2012 ; Lingle and Riede, 2014 ), it is often suggested that rough sounds could elicit unpleasantness in many species as well.…”