When it comes to animal models of human speech, songbirds are the gold standard. Scientists look to birds, and not other mammals, for clues about human speech because most mammals produce simple, monosyllabic, innate vocalizations that are much less flexible than those of birds. Birds sing complex, multisyllabic songs composed of multiple elements with flexible syntax (i.e., the way in which elements are ordered and combined). And both humans and songbirds possess neural circuits that support vocal plasticity that are thought to be absent in other mammals.
Cetaceans (whales and dolphins) and bats may be the exceptions. These animals have evolved a suite of neural adaptations to support echolocation, and they are the only two groups of mammals that demonstrate vocal learning, juvenile babbling, regional dialects, and cultural transmission of vocalizations.
Of the bats, the Brazilian free-tailed bat (Tadarida brasiliensis) is of special interest because it is a mammal that sings like a bird. This bat’s songs are hierarchically structured with specific syllables combined to form phrases, which are in turn combined to form complex songs. Song construction follows rules but specific syntactical arrangements vary from one song rendition to the next.
Florida International University biologist Kirsten Bohn, in collaboration with colleagues from Texas A&M University, has recently discovered that Brazilian free-tailed bats vary the syntax in their songs in response to different social situations. The research was published in June in Animal Behaviour.
Click to read more about Prof. Bohn's discovery on Brazilian free-tailed bats.