The relationship between echolocation frequency (represented by dominant frequency, DF for short) and body size (body mass, forearm length and body length) in 8 species of horseshoe bats ( Rhinolophus cornutus, R. affinis, R. thomasi, R. rouxi, R. blythii, R. ferrumequinum, R. pearsoni, R. rex ) was examined. The eight species were captured in caves in five regions (Guiyang, Anlong, Xingyi, Anshun and Zhenning) of Guizhou Province in July and August 1999 and June 2000. The species were identified based on the descriptions in Mammals of GuiZhou (Luo et al .)and Key to the Identification of Chiroptera (Wang, unpublished). The bats were captured at the entrance to the caves at about 8 pm (the time when bats usually leave the caves), and were then put into a recording room near the capture locations where they could fly freely. Recordings of their echolocation calls were made bout 2 hours later using an ultra sound detector (U30, Ultra Sound Advice, UK) which recorded the calls of bats that were flying directly at the microphone at a distance of 1 m. Each bat was recorded 5 times and the signals were fed into a portable ultra sound processor (PUSP, Ultra Sound Advice, UK). The duration for recording was 1 1 s with a sampling frequency of 44 1 kHz. By replaying the recorded tapes the best quality recordings (the loudest and clearest with the least background noise) were replayed at 1/10 speed and re recorded using a digital sound recorder (Sony, MD 1, frequency response range: 30～20 000 Hz). The re recorded echolocation signals were analyzed using the sound processing software Cool Edit 2000, developed by the American Syntrillium Software Company. Ultra sound analysis referred to the sound spectrograms (frequency time graph), time domain spectrograms (energy time graph), energy spectrograms (energy frequency graph), and Hanning window to obtain an analytic precision of 256 Hz. The analysis attenuation was 60 dB. The DF, pulse duration and interpulse interval of the echolocation calls were recorded and the duty cycle
When they are flying,Great evening bat ( Ia io ) produces short FM echolocation calls including three harmonics,of which the first one and the second one are stronger.As they fly,the first harmonic is modulated from 49 0 to 18 3 kHz,the second one is modulated from 80 0 to 35 6 kHz,and the third one from 87 2 to 56 7 kHz.The average duration of the calls is 3 7 ms.It was predicted that Great evening bat ( Ia io ) captures big insects in the open area among foliages according to the sound characteristic analysis of echolocation calls and the analysis comparing with the echolocation calls of other bats that perch in the same cave.
