River otters in Brazil use a complex range of vocalizations to communicate, according to a new study published by PLOS. The researchers identified six clearly distinguishable call types at frequencies ranging from 90 to 2500 Hz.
Among 13 species of otters, some are completely solitary while others are highly sociable. The giant otter is known to use a complex collection of vocalizations., but the social calls of the other species have remained largely unknown.
“Most aquatic mammals have complex social and communication systems. Interestingly, little is known about otters’ vocal communication compared to other aquatic mammals,” wrote the study authors.
“Here, for the first time, we acoustically describe vocalizations of the neotropical otter (Lontra longicaudis), a solitary and endangered New World otter species.”
For their investigation, the researchers observed the behavior of six captive river otters on Santa Catarina Island in Brazil. Overall, they analyzed nearly 1,000 calls.
“We used 422 high-quality recorded calls, along with 990 call occurrences including behavioral context to establish the vocal repertoire of the neotropical river otter,” wrote the study authors. “The vocal repertoire was classified into six call types: chirps, squeaks, chuckles, growls, hahs and screams.”
The calls identified by the experts, as well as the range of frequencies, were found to be used in different social contexts. For example, high-frequency chirps and low-frequency chuckles were primarily used by males to reaffirm social bonds or to beg for food.
Females often produced low-amplitude squeaks during social grooming, and “hahs” to express alarm or surprise at a new object. They also used high-frequency screams to complain, both during play and in more aggressive contexts.
Both males and females frequently used low-pitch growls in disputes over food or individual space.
According to the study authors, a better understanding of the vocalizations of neotropical river otters could enable conservationists to make use of acoustic recordings to monitor this elusive endangered species.
“The neotropical river otter has a rich vocal repertoire, with at least six distinct call types, similar in complexity to other solitary otter species but less complex than that of the social giant otter. Despite differences in sociality, phylogeny and ecology, L. longicaudis seems to possess vocalizations homologous to those found in other otters (e.g. hah and chirp), suggesting phylogenetic inertia in the otter communicative repertoire.”
The study is published in the journal PLOS ONE.