A frog that eats foam: predation on the nest of Polypedates sp. (Rhacophoridae) by Euphlyctis sp. (Dicroglossidae)

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Predation is one of the most widespread foraging behaviour prevalent in the animal kingdom (Curio 1976;Taylor 1984). Amphibians, with respect to predation, generally prefer waiting for prey while being stationary as a method for foraging (i.e., ambush predation) (Duellman & Trueb 1986). It is to be noted here that visual detection is the primary method with which anurans spot prey (Freed 1988).
In this note we report a predation behaviour on the foam nest of one species of anuran (Polypedates sp.) by another species (Euphlyctis sp.).
Observations: An individual of Euphlyctis sp. was observed feeding on a foam nest of Polypedates sp. on 14 March 2020 at 09.42h (Image 1). The observation was made on top of Barunei Hills, in the Khurda District of the state of Odisha in India (20. 157°N & 85.643°E, 227m). The weather was clear and sunny with an ambient temperature of 32ºC. It was an opportunistic observation made while inspecting amphibians in an ephemeral pool of water inside a small cave on top of a stunted hill. The pit was observed to harbour a community of three species of anurans-Euphlyctis sp., Polypedates sp. and a Duttaphrynus sp. We observed an individual of Euphlyctis eating, with gulping motion, from one of the foam nests of the Polypedates sp. that was at the side of the water pool on a rock substratum, intermittently. The observation was captured in video and photographs were created using the snapshot from the videos for visual reference. The image and video files were submitted to the Lee Kong Chian Natural

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History Museum of the National University of Singapore digital repository for reference. The accession numbers are provided in Table 1 given below. The video files have also been deposited into figshare repository (https:// figshare.com/ with the following DOI: https://doi. org/10.6084/m9.figshare.12720617). After recording the aforementioned behaviour, the frog was left undisturbed. Identification of the observed individuals was conducted till genus level as it was in a field setting and no morphometrics and meristic data were collected for comparison. Hence, in that respect, it would be difficult to identify the organisms up to the species level.
Discussion: Scavenging has been reported in some species of anurans (Nishikawa & Ochi 2016;Gazdar et al. 2019). Besides predation and scavenging, oophagy and cannibalistic behaviour have also been reported from some species (Crump 1983(Crump , 1992Rajput et al. 2011;Mahapatra et al. 2017). Predation on anuran foam nest has been reported from arthropods and snakes (Villa et al. 1982;Menin & Giaretta 2003); however, this behaviour has not been reported from anurans till date. Generally, amphibians are considered to be opportunistic in their feeding habits, in contrast, empirical studies have suggested that some species may be selective (Duellman & Trueb 1986). Feeding mechanisms in adult anurans involves a flick of the lingual region where the postero-dorsal surface becomes antero-ventral surface of the fully extended tongue (Regal & Gans 1976). In this recorded observation, however, we notice a gulping mechanism of feeding on the foam nest without the use of the lingual region.
Anurans are key components in an ecosystem serving both as predator and prey thus linking a variety of trophic levels and maintaining the trophic structure in the ecosystems (Duellman & Trueb 1986). Similar observations and further focus on these behaviours would help us understand the diversity in the range of foraging behaviour in amphibians. This will in turn help us acknowledge ecosystem dynamics in terms of interaction of trophic levels as well as interrelationships among different families of amphibians with respect to predator and prey relationships.  www.threatenedtaxa.org The Journal of Threatened Taxa (JoTT) is dedicated to building evidence for conservation globally by publishing peer-reviewed articles online every month at a reasonably rapid rate at www.threatenedtaxa.org. All articles published in JoTT are registered under Creative Commons Attribution 4.0 International License unless otherwise mentioned. JoTT allows allows unrestricted use, reproduction, and distribution of articles in any medium by providing adequate credit to the author(s) and the source of publication.