An Acoustic Analysis of the Genus Microhyla (Anura: Microhylidae) of Sri Lanka

Abstract

Vocalizing behavior of frogs and toads, once quantified, is useful for systematics, rapid species identification, behavioral experimentation and conservation monitoring. But yet, for many lineages vocalizations remain unknown or poorly quantified, especially in diversity rich tropical regions. Here we provide a quantitative acoustical analysis for all four Sri Lankan congeners of the genus Microhyla. Three of these species are endemic to the island, but Microhyla ornata is regionally widespread. Two of these endemics, M. karunaratnei (Critically Endangered) and M. zeylanica (Endangered), are highly threatened montane isolates; the other, M. mihintalei, is relatively common across the dry lowlands. We recorded and analyzed 100 advertisement calls from five calling males for each species, except for M. zeylanica, which only had 53 calls from three males suitable for analyses. All four species call in choruses and their vocal repertoires are simple compared to most frogs. Their calls contain multiple pulses and no frequency modulation. We quantified eight call characters. Call duration and number of pulses were higher for the two montane isolates (inhabiting cooler habitats at higher altitudes) compared to their lowland congeners. Microhyla zeylanica has the longest call duration (of 1.8 ± 0.12 s) and the highest number of pulses (of 61–92 pulses). The smallest of the species, Microhyla karunaratnei (16.2–18.3 mm), has the highest mean dominant frequency (3.3 ± 0.14 kHz) and pulse rate (77 ± 5.8 pulses per second). The calls separate well in the Principal Component space: PC1 axis is mostly explained by the number of pulses per call and call duration; PC2 is mostly explained by the pulse rate. A canonical means plot of a Discriminant Function analysis shows non-overlapping 95% confidence ellipses. This suggests that some call parameters can be used to distinguish these species effectively. We provide detailed descriptions for eight call properties and compare these with congeners for which data is available. This work provides a foundation for comparative bioacoustic analyses and species monitoring while facilitating the systematics of Microhyla across its range.

Acoustic divergence in advertisement calls among three sympatricMicrohylaspecies from East China

“…To the best of our knowledge, the present study is the first to report the advertisement call of M. beilunensis consisting of 2-7 pulses per call, which has relatively few NPs among the 29 studied Microhyla species. Similar to that in other Microhyla species reported previously (Wijayathilaka, Meegaskumbura & Gianni, 2016;Sun, 2017;Nguyen et al, 2019;Poyarkov et al, 2019;Garg et al, 2018), oscillograms and spectrogram of advertisement calls in M. beilunensis were conformed to the pulse-repetition sound based on Beeman's (1998) sound categories. The patterns of variation in call parameters of anurans are correlated with female preferences and different parameters contain different kinds of biologically significant information (Gerhardt, 1991).…”

“…Our results showed that spectral parameters (e.g., DF, F1 and F3) are under the physical body size constraint, with smaller individuals producing calls at higher frequencies; in contrast, temporal parameters were not influenced by body size in the three Microhyla species. Similar results were also found in other Microhyla species (Wijayathilaka, Meegaskumbura & Gianni, 2016) indicating that spectral parameters of calls might encode the information of male's body size in each Microhyla species. Therefore, researchers suggested that the spectral parameters of anurans' advertisement calls, as an honest signal, transfer information about the body size of vocalizing individuals and thus, possibly information about its strength and quality to females and competitors (Davies & Halliday, 1978;Wells, 2007).…”

“…To date, there are reports on the advertisement calls of 28 Microhyla species (Table S1). Several studies have reported the taxonomy and identification of Microhyla species in some distribution areas (Sri Lanka, Myanmar and South Asia) through bio-acoustic comparison (Wijayathilaka, Meegaskumbura & Gianni, 2016;Garg et al, 2018;Poyarkov et al, 2019). In East China, M. beilunensis Zhang et al (2018), M. fissipes Boulenger (1884) and M. heymonsi Vogt (1911) are three common Microhyla species and their distribution ranges are overlapping (Fig.…”

A new species of the Asian music frog genus Nidirana (Amphibia, Anura, Ranidae) from Southwestern China

“…The sound files in wave format were resampled at 48 kHz with sampling depth 24 bits. Calls were recoded and examined as described by Wijayathilaka & Meegaskumbura (2016). Call recordings were visualized and edited with SoundRuler 0.9.6.0 (Gridi-Papp 2003-2007 and Raven Pro 1.5 software (Cornell Laboratory of Ornithology, Ithaca, NY, USA).…”

<b>An annotated checklist of the herpetofauna of the Rashtrapati Bhawan Estates, New Delhi, India</b>

“…A second individual was sighted the next day from the same area. The pulsatile and short advertisement calls of the pool breeder M. ornata (Wijayathilaka & Meegaskumbura 2016) was also heard from another spot in the kitchen-garden area after a heavy downpour on 11 July 2015 when most of the area was waterlogged. …”