Constant-frequency and frequency-modulated components in the echolocation calls of three species of small bats (Emballonuridae, Thyropteridae, and Vespertilionidae)

The echolocation calls of Rhychonycteris naso (Emballonuridae), Thyroptera tricolor (Thyropteridae), and Myotis riparius (Vespertilionidae) were recor ded at the Ceno Palma Field Station in Costa Rica in February 1998. All thr ee species produced echolocation calls at low duty cycle (signal on similar to 10% of the time). While T. tricolor produced low-intensity echolocation calls that were barely detectable when the bats were < 0.5 m from the micr ophone, the other two species produced high-intensity calls, readily detect able at distances > 5 m. Myotis riparius produced calls that swept from abo ut 120 kHz to just over 50 kHz in about 2 ms. We found no evidence of harmo nics in these calls. Rhynchonycteris naso and T. tricolor produced multihar monic echolocation calls. In R. naso the calls included narrowband and broa dband components and varied in bandwidth, sweeping from just under 100 kHz to around 75 kHz in over 5 ms. Most calls were dominated by the higher harm onic (ca. 100 kHz), but some also included a lower one (ca. 50 kHz). The ca lls of T. tricolor were 5-10 ms long and dominated by a single frequency (c a. 45 kHz), sometimes with a ca. 25 kHz component. The echolocation calls o f all three species included frequency-modulated and constant-frequency com ponents. While these terms describe the components of the echolocation call s, they do not necessarily describe the bats' echolocation behaviour.