. Bonner zoologische Beiträge : Herausgeber: Zoologisches Forschungsinstitut und Museum Alexander Koenig, Bonn. Biology; Zoology. 116 Bonner zoologische Beiträge 52 (2004) cilloscope, Toennies Recordine camera; recording speed 250 mm/s). The spectrograms were prepared with the pro- gram BatSounds. For the mathematical treatment of the da- ta GraphPad Prism, Version , and Statgraphics, Version were used. Until recently a call in the case of tree frogs was conside- red to be a single pulse group. This was appropriate to the situation in H. meridionalis, because in this species both the ca
. Bonner zoologische Beiträge : Herausgeber: Zoologisches Forschungsinstitut und Museum Alexander Koenig, Bonn. Biology; Zoology. 116 Bonner zoologische Beiträge 52 (2004) cilloscope, Toennies Recordine camera; recording speed 250 mm/s). The spectrograms were prepared with the pro- gram BatSounds. For the mathematical treatment of the da- ta GraphPad Prism, Version , and Statgraphics, Version were used. Until recently a call in the case of tree frogs was conside- red to be a single pulse group. This was appropriate to the situation in H. meridionalis, because in this species both the calls and the intervals between them are very long, so that each call represents an individual sound event. Howe- ver, in tree-frog species with short pulse groups and inter- vals a call consists of a series of pulse groups. This termi- nology is used here, as was already the case in the first studies of the adveitisement call of H. a. arbórea (Schnei- der 1966, 1967). To obtain the values for the pulse groups, intervals and pulses per group, in about the middle of a call three pulse groups and the associated intervals were mea- sured, the number of pulses per pulse group detennined and the means of these were used for the calculations. 3. RESULTS Calling behaviour At the two sites Colfiorito and Anchione, the tree frogs began producing their advertisement calls (Fig. 1) at. 100 ms Fig. 1. Oscillograms showing sections of two advertisement calls, recorded at the air temperatures °C (above) and °C (below). During the same period of time three pulse groups are produced at the lower temperature and five at the higher one. about 19:30 CET, when twilight was well advanced. Ini- tially the pauses between calls were relatively long, 5- 40 s. As it grew darker the calling was more persistent, with inter-call intervals shorter than 5 s. At Colfiorito the air temperature when calling began was only slightly above the lower threshold for calling. One male, uninfluenced by t
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