Scopioricus spatulatus

behaviour · bio.acousti.ca

(4 males recorded) S. spatulatus is a conspicuous acoustic presence in disturbed forest near the Refugio Turistico La Pastora, Ucumari. Its calls are loud, easily audible and the males soon sing readily in captivity. (This is especially true in transit.) Callers engage in bouts of singing activity separated by substantial silent periods. For one male (96-2) at 19°C we measured a mean interval between calling bouts of 70s. Each bout is comprised of a number of zips; the aforementioned male had an average of zips per bout of 11 (range 9-16). Each Zip is either 4 or 5 phonatomes and each phonatome a pair of rapid-decay pulse trains. Fig. 43 A shows a single zip of 5 phonatomes or 10 pulse trains. The pulses are transient and discrete, each with an nearly complete-to-background exponential decay before the next pulse occurs. The following AM parameters are pooled averages for two males both recorded at 19°C: zip duration 401 ms, 1.4 s intervening between zips; 5 phonatomes/zip; phonatome period 76ms; first train of the phonatome 33 ms, second train 35 ms; first train with 40 pulses, second with 41: pulse rate 1225/s first train, 1175 second train. One of the above males and another were recorded at 12°C, a typical field temperature for this species; their pooled averages for most of the same measures are: zip duration 619 ms, 3.6 s intervening between zips: 4 or 5 phonatomes/zip: phonatome period 129 ms; first train of the phonatome 58 ms, second train 65 ms. This species has a bimodal band spectrum (n = 2 males) with a very marginally more intense ultrasonic peak at 22.9 kHz and an audio peak at 8.3 kHz (Fig. 43C). The two peaks are consistent features of a broad band of frequencies extending from 6 to 34 kHz if one considers only energy within 20 dB of the maximum peak. The direction of stroke makes no difference in the spectrum: the spectra of Figs 43 C, E are identical. The approximate equality in amplitude and duration of successively distinctive pulse trains is an uncommon AM feature for a katydid song. It is common for non-resonant generating species eg: Conocephalus to exhibit a markedly shorter and lower intensity train preceding a longer and much more intense train. But here the two alternating types are virtually equal in both duration and amplitude. A listener receives the impression that the singer changes direction with each successive train as in the sounds of to and frostrokes made when sawing wood. Displacements of the tegmina during the zip were readily followed witht he human eye and so direct observation could confirm the occurrence of apprixmately equal sound-effective strokes in opposite directions. There is some similarlity int he file structure of this species (Fig. 29) and that of S. exarmata (Fig. 25).

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