May 26 (UPI) -- The neotropical otter of Brazil uses a surprisingly rich vocal range when communicating, according to a study published Tuesday in the journal PLOS One.
Studies of otter vocalization have mostly focused on the most sociable species, South America's giant river otter, which is the longest member of the weasel family.
Giant otters live in family groups of three to eight individuals, whereas the neotropical otter, native to Central and South America, is mostly solitary.
For the new study, scientists recorded the vocalizations of six captive neotropical otters in Brazil. Analysis of the more than 1,000 recorded vocalizations revealed six different types of calls, ranging in frequency form 90 to 2500 hertz.
Scientists observed males regularly using both low-frequency "chuckles" and high-frequency "chirps" to strengthen social bonds and beg for food.
During grooming and play, females produce low-amplitude "squeaks." When females spot unfamiliar objects, they often emit "hahs," or alarm calls.
Meanwhile, high-frequency yelps can be used in both playful and more aggressive contexts.
While squaring off in disputes over food and territory, both males and females use tonal, low-pitch "growls" in an attempt to scare off their rival.
The findings suggest the vocabulary of the neotropical otter is just slightly more expansive than the solitary North American river otter, Lontra canadensis, which uses four different calls.
Meanwhile, the giant otter, the most gregarious of the 13 members of the otter subfamily, vocalizes 22 distinct calls.
"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," researchers wrote in their paper.