Bioacoustics of Ptenopus kochi

Advertisement call. (Figs 3 , 20 H ) Consists of 13 notes (range 11–19) uttered in rapid succession with a note rate of 7.90s - 1 (range 5.98–10.33). Note duration is short (27 ms [range 18–40]) and relatively regular, sometimes slightly shorter as the call progresses, with note 1 duration deviance low (20 % [range 6–31]). The inter-note intervals are usually short (98 ms [range 75–130]) and regular with inter-note interval range low (30 % [range 14–52]). Median call density is high (0.28 [range 0.20–0.34]) and call duration long ( 1.6s [range 1.2–2.4]). The basal frequency is 382 Hz (range 301–492) but very soft and may be inestimable, with harmonic bands louder towards the upper dominant frequencies, the upper at 3.3 kHz (range 3.1–3.88) and a clear lower dominant frequency around 1.4 (range 1.1–1.9) kHz, about half the upper dominant frequency. Frequency appears to remain constant throughout the notes and call, as is the case with the (human) perceived pitch. Bandwidth (90 %) is difficult to estimate consistently: approximately 0.7–4.9 kHz. This species calls more intensively and for a shorter period of time than its sympatric or parapatric congeners ( P. carpi , P. maculatus and P. circumsyrticus sp. nov. ). Calling also commences earlier in the day than these congeners. Call period (mean 74 s) varies greatly, but can be as low as 9 seconds during peak chorus activity. Calling activity is crepuscular, commencing shortly before or at sunset, and ending at nightfall. Sporadic calls may occasionally be heard later at night, in the morning, or on overcast days ( Haacke 1969 ).

Natural history. Breeding generally occurs from September to December ( Polakow 1997 ), but this species may occasionally call throughout much of a year following above-average rainfall. Rainy weather may cause calling activity to cease for days to weeks. It has previously been characterised as being nocturnal ( Haacke 1969 ), but is more crepuscular. This species is more frequently observed on the surface during the day (e. g., Murray and Lease 2015 ) than congeners, except perhaps for P. circumsyrticus sp. nov. Courtship appears to be more complex than in other species, and also more variable. Some courtship encounters witnessed by FB were similar to that of P. maculatus , with the female simply approaching the calling male and the male responding with a few calls. The female then scratches rapidly at the burrow entrance to indicate she wants to enter, after which the male retreats backwards and the female follows him inside. In other encounters, the males may exit the burrow and display their gular patch to the approaching female. Yet more variations, including mutual head bobbing and soft vocalisations, have been observed ( Polakow 1997 ). In some cases, the female may inspect the burrow of a potential suitor, entering through one opening and leaving through another soon after, if she (presumably) finds the burrow unsuitable ( Polakow 1997 ). Mating takes place within the burrow, with the male usually uttering something similar to the advertisement call from within the burrow, after a female has entered. Fighting is common among closely-spaced males. In one observation (FB), a young male charged a much larger calling male at its burrow entrance, from several metres away. The two animals stood belly-to-belly on their back legs, rapidly clawing one-another with their hands for one or two seconds, before the younger male retreated. Scars from bite-marks on the body are commonly observed in both sexes, but more often in males. The burrows of P. kochi tend to be more complex than other species, often with more than one entrance ( Polakow 1997 ; FB observations). Males, females, and hatchlings share burrows for extended periods of time, and a male and female will generally use separate entrances to the same burrow system. See Polakow (1997) and Haacke (1964 , 1978) for additional notes on P. kochi courtship and ecology.