Bioacoustics of Austrodontura castletoni

Remarks. A. casteltoni was found to be abundant in forest edge habitats of the coastal scarp forest within the small Silaka Nature Reserve near Port St. John’s. Forests in this reserve are some of the last remaining fragments of the once more widespread forests of the Transkei Coastal Belt, which exhibit exceptionally high levels of botanical endemism and are biogeographically ancient ( Mucina and Rutherford 2006 ). The katydids were found, often in densities of 3–5 individuals/m2, on herbaceous vegetation at shaded edges of the forest and on lower branches of Acacia karroo Hayne. Multiple individuals were observed feeding on buds and bark of A. karroo , both during the day and at night. Individuals of A. castletoni were are also seen frequently on the invasive plant Lantana camara L., but no feeding on this plant was observed. Male stridulation was recorded only at night, beginning at around 21:00. The sound produced by the males was entirely within the ultrasonic range, and no energy was detected below 25 kHz, as measured by the Petersson D200 ultrasound detector; the highest range of the call reached 120 kHz, but we were unable to detect its uppermost limit due to the limitations of the equipment. At 26°C the male call consisted of a series of 3–8 short (0.206–0.735 sec) echemes, usually followed by a single longer echeme lasting 1.25– 5.0 s ; each echeme consisted of short syllables lasting 0.028– 0.042 s (± 0.0032, n=30) ( Fig. 3 ). Conspecific males present in the vicinity of the caller often began calling in the second half of the long echeme of the principal caller. We were unable to obtain an unambiguous recording of a female, but single, ultrasonic ticks were later found between several calls of the males, and the presence of distinct stridulatory files on the right tegmen of the female suggests that this species engages in courtship duetting.