1) Vocal dialects in Brazilian Free-Tailed Bats (Tadarida brasiliensis)

Israel Salazar is working on one of our main projects.  He is testing whether 1) songs vary across regions (vocal dialects) and 2) whether males modify songs with social experience. For his first question he has recorded songs from Georgia throughout Florida to Miami as well as in Puerto Rico and Jamaica. For the second question he is developing long term playbacks aimed at resident males at wild colonies in Miami. Playbacks will mimic similar or dissimilar males “moving in next door”. We predict that males may 1) modify songs to become more similar to new dissimilar males (a form of increasing aggression seen in some songbirds) or 2) males may diverge from similar males to reduce overlap and increase the salience of their songs. He is looking at syntactical changes (the order and number of phrases within songs) as well as the acoustic shape of Chirp B syllables. Giselle and Marcella are also assisting with this project.

  1. 2) Vocal production in Tadarida brasiliensis

The majority of animal vocalizations including mammals are innate, do not require audio-vocal feedback and do not have repeatable patterns of multiple types of syllables. These vocalizations are produced by simple neurocircuitry in lower brain centers that is in marked contrast to human speech. Birdsong however shares four characteristics with speech that are not seen in other animals (except cetaceans and bats):

  1. 1)Songs require audio-vocal feedback (like bats use for echolocation),

  2. 2)Songs are learned,

  3. 3)Songs have specific patterns and syntax,

  4. 4)Songbirds show vocal flexibility.

These four characteristics are supported by specialized neurocircuitry. This is why songbirds our our main speech production model. Do Tadarida brasiliensis have vocal production circuitry more like a typical mammal or more like songbirds (and humans)? We are working on this question with Michael Smotherman at Texas A&M University.

T. brasiliensis Song Primer - Songs are composed of three types of phrases Chirp, Trill and Buzz. Trills and buzzes are made of only a single syllable type (trill and buzz respectively). Chirp phrases are composed of two syllable types: Chirp A and Chirp B. The figure on the right shows three songs. The top two (a and b) are from the same bat and the bottom song (c) is from a different bat. Note that for each bat the shape of the syllables remains constant between songs but the order and number of phrases changes between songs as do the number of Chirp A and Chirp B syllables. For the bottom panel (c) note that the Chirp A and especially Chirp B syllables of the second bat are markedly different than the first bat. Figure from Animal Behaviour 85:1485-91.