Bioacoustics of Ptenopus garrulus

Advertisement call. The advertisement call (Figs 3 , 20 A ) consists of 5.4 notes (4–6) uttered in rapid succession, with a note rate of 5.28s - 1 (range 3.76–7.37). Note duration is short, 22 ms (range 16–31), and highly regular, with note 1 deviance 15 % (range 3–27 %). Inter-note intervals are short (168 ms [range 114–234]) and regular, although latter intervals can be slightly longer; inter-note interval range 14–34 %. Call density relatively low (0.13 [range 0.09–0.18]). Call duration is very short, only 0.86s (range 0.6–1.2). The basal frequency is ~ 450 Hz (range 373–508) but very soft and may be inestimable, with harmonic bands louder towards the dominant frequency at 4.2 kHz (range 3.9–5.1); a very slight lower peak frequency band is evident at around or just below half the dominant frequency (roughly 1.3–2.6 kHz, cannot always be reliably estimated). Frequency appears to modulate briefly up, then down by ~ 100 Hz with each note, or remain constant. The (human) perceived pitch tends to be higher than that of most other species. Bandwidth (90 %) is difficult to estimate consistently: approximately 0.6–8.2 kHz, usually wider than other species. During peak chorus activity, this species calls much more frequently than most other species, the call period being very short: mean 25 s, and as low as 4 s. However, calling activity is short in most localities visited by the author, usually commencing around 20 min after sunset, and lasting only 20–40 mins. Calling may continue later if the moon is above the horizon and conditions are warm, but at an extremely decreased rate. More extensive and intensive choruses, lasting throughout the night, have been recorded shortly after rain ( Haacke 1969 ).

Natural history. The main calling period coincides with the breeding season ( Hibbitts et al. 2012 ). In the northern limits of its distribution, the main breeding season appears to be between June and early September, but moves later southward (author observations). Most observations on this species were made in the southern Kalahari. Here, they breed between September and November (see Hibbitts et al. 2005 , although this includes data from several Ptenopus species in addition to P. garrulus ; Hibbitts et al. 2012 ) and possibly until late January, as hatchlings (< 32 mm SVL ) have been recorded beween October and May ( Haacke 1975 ), and yolked eggs were recorded within females between late August and late January ( Pianka and Huey 1978 ). Clutch size appears to be one egg, although a second clutch may develop shortly after the first ( Hibbitts et al. 2005 ). One nest was found to contain three eggs, although one or two of these may have been Pachydactylus wahlbergi ( Haacke 1975 ) . Minimum recorded hatchling SVL was 23.7 mm ( Haacke 1975 ). Haacke (1969) observed P. garrulus calling during March at the Nosob Camp, Kgalagadi-Gemsbok National Park, South Africa , after a rainfall event, suggesting that rainfall may cause bouts of calling outside the normal breeding season. During the observed event, the geckos called throughout the night, rather than the normal calling period around sunset. A similar observation was made at the Aha Hills, Namibia (northern portion of the distribution), during early February (Predinger pers. com.). For further notes on natural history and behavioural ecology of P. garrulus , seesee Hibbitts and Whiting (2005) , Hibbitts (2006) , Hibbitts et al. (2007 , 2012 ).