THE ASSEMBLAGE OF ACOUSTICALLY COMMUNICATING CRICKETS OF A TROPICAL EVERGREEN FOREST IN SOUTHERN INDIA: CALL DIVERSITY AND DIEL CALLING PATTERNS

ABSTRACT

This study provides the first description of the call structures of twenty ensiferan species constituting the nocturnal acoustic community of an evergreen forest in Southern India. Of the twenty species, ten belonged to the superfamily Grylloidea, nine to the superfamily Tettigonioidea and one to the superfamily Gryllacridoidea. The calls of the gryllid species were narrow-band with dominant frequencies ranging from 3–7 kiloHertz. The calls of the tettigoniids covered a wide spectral range, reaching far into the ultrasound in some species. Four of the nine tettigoniid species had narrow-band, relatively low frequency calls centred at 3, 9, 11 and 15 kiloHertz respectively. The temporal patterns of the species were diverse, with syllable durations ranging from eight to 63 milliseconds and syllable periods from 17 milliseconds to two seconds. The calls of the species showed considerable overlap in both spectral and temporal features. Calling activity peaked between six o'clock in the evening and midnight and died down subsequently. We found no diel partitioning of calling time between acoustically communicating ensiferan species. Species accumulation curves suggest that the acoustic community has been almost completely sampled.

Keywords:

• acoustic community
• diel calling patterns
• Ensifera
• India
• tropical forests