Bioacoustics of Yoyetta crepita

Distribution, habitat and seasonality. ( Plate 6E–F , Fig.1 ). At present, Yoyetta crepita sp. nov. has only been captured around Clandulla and Kandos in the Bylong Valley, NSW ( Fig. 1 ). This species appears to favour smooth barked eucalypts, particularly Eucalyptus melliodora (Yellow Box) and the rough-barked E. cannonii (Capertee Stringybark) . Individuals are located in the upper reaches of the eucalypts> 10m from ground level, but may descend briefly to lower levels during ticking flights (see “calling song”). At Clandulla, Y. crepita sp. nov. cohabits with Y. humphreyae Moulds & Popple , Y. timothyi Emery, Emery & Popple , Y. psammitica Emery, Emery & Popple and an additional undescribed Yoyetta species. Most specimens have been present from mid-November to late-January.

Calling song ( Fig. 8 ). The male calling song of Y. crepita sp. nov. is a series of sharp, rapid ticks. Following analyses of the calling song structure (all statistics, n =3 from Clandulla locality), Fig. 8 shows each ‘tick’ is a single syllable between 0.005 and 0.016 s duration, and the gap between syllables ranges from 0.159 to 0.185 s duration. The frequency plateau ranges from 9 to 14.4 kHz, with a dominant frequency approximately between 10.5 and 11.9 kHz ( Fig. 8C ). Groups of male Y. crepita sp. nov. emit a distinctive, rapid clicking chorus from the resident population at around 5 min intervals when sunny (and cease mid-chorus with any cloud cover). During these choral cacophonies, males may relocate, calling in flight and often resting for short intervals at lower heights before resuming flight. This behaviour is likely aimed at finding responding females, as males respond readily to finger clicking during the chorus, particularly when present in large numbers. Males may also call for brief periods when resting. Females are usually found on the main trunks around 5m from ground and have been observed wing-flicking during the chorus. The calling song of Yoyetta crepita sp. nov. closely resembles those of Y. australicta Popple & Emery , which also produces single pulses. While both species have broad frequency plateaus, the pulse gap of Y. australicta is 0.27– 0.67s , greater than for Y. crepita sp. nov. (< 0.19s ). In addition, males of Y. crepita sp. nov. do not emit quiet macrosyllables at the end of their bouts of ticking.