Journal of Threatened Taxa | | 26 October 2020 | 12(14): 17041–17044


ISSN 0974-7907 (Online) | ISSN 0974-7893 (Print) 


#6291 | Received 11 June 2020 | Final received 28 July 2020 | Finally accepted 28 August 2020



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


Pranoy Kishore Borah 1, Avrajjal Ghosh 2, Bikash Sahoo 3  & Aniruddha Datta-Roy 4


1–4 National Institute of Science Education and Research (NISER), Homi Bhabha National Institute (HBNI), Bhubaneswar, Jatni, Khurda, Odisha 752050, India.

1 (corresponding author), 2, 3, 4



Editor: Neelesh Dahanukar, Indian Institute of Science Education and Research, Pune, India.      Date of publication: 26 October 2020 (online & print)


Citation: Borah, P.K., A. Ghosh, B. Sahoo & A. Datta-Roy (2020). A frog that eats foam: predation on the nest of Polypedates sp. (Rhacophoridae) by Euphlyctis sp. (Dicroglossidae). Journal of Threatened Taxa 12(14): 17041–17044.


Copyright: © Borah et al.  2020. Creative Commons Attribution 4.0 International License.  JoTT allows unrestricted use, reproduction, and distribution of this article in any medium by providing adequate credit to the author(s) and the source of publication.


Funding: Intramural financial support from the Department of Atomic Energy, Govt. of India, through National Institute of

Science Education and Research (NISER) for facilitating this study.


Competing interests: The authors declare no competing interests.


Acknowledgements: The authors are thankful to Dr. Chan Kin Onn, Museum Officer (Lecturer), Herpetology (Systematics & Evolution), Curator of Amphibians & Reptiles, Lee Kong Chian Natural History Museum, National University of Singapore.  We would also like to thank Mr. Krishnendu Banerjee, for assisting us with the literature.  Finally, we would like to thank the School of Biological Sciences, National Institute of Science Education and Research, Bhubaneswar, Odisha, India for the departmental and logistical support.



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).

At least six families of amphibians are known to produce foam nests for egg laying, namely: Hylidae, Hyperoliidae, Leptodactylidae, Microhylidae, Myobatrachidae, and Rhacophoridae (Haddad et al. 1990; Andreone et al. 2005; Haddad & Prado 2005).  Various hypothetical functions have been attributed to foam nests of frogs.  These include inhibition to the growth of tadpoles (Pisano & Del Rio 1968), resistance to desiccation (Ryan 1985; Downie 1988), improvement towards the supply of respiratory gases (Seymour & Lovebridge 1994), regulation of temperature (Downie 1988), predator defense (Downie 1988, 1990), as a source of food (Tanaka & Nishihira 1987), and also growth acceleration (Prado et al. 2005).  Predation on foam nest has previously been reported, where non-anuran species have been seen to predate on these nests in various conditions (Villa et al. 1982; Lingnau & Di-Bernardo 2006).

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 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 ( with the following DOI:  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, 1992; Rajput 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.



Table 1. Accession numbers of files deposited in Lee Kong Chian Natural History Museum, Zoological Reference Collection, National University of Singapore.

File type

Accession number

Video files

ZRC(IMG) 1.195a

ZRC(IMG) 1.195b

ZRC(IMG) 1.195c

ZRC(IMG) 1.195d

ZRC(IMG) 1.195e

ZRC(IMG) 1.195f

Snapshots from the videos

ZRC(IMG) 1.194a

ZRC(IMG) 1.194b

ZRC(IMG) 1.194c

ZRC(IMG) 1.194d

ZRC(IMG) 1.194e


ZRC(IMG) 1.196a

ZRC(IMG) 1.196b

ZRC(IMG) 1.196c

ZRC(IMG) 1.196d

ZRC(IMG) 1.196e

ZRC(IMG) 1.196f

ZRC(IMG) 1.196g

ZRC(IMG) 1.196h

ZRC(IMG) 1.196i

ZRC(IMG) 1.196j

ZRC(IMG) 1.196k



For image - - click here





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Marler, T.E. & A.J. Lindstrom (2020). Leaf nutrients of two Cycas L. species contrast among in situ and ex situ locations. Journal of Threatened Taxa 12(13): 16831–16839.


Table 2. Green leaf nitrogen concentration (mg·g-1) of Cycas micronesica and Cycas nongnoochiae plants in various locations. Ex situ sites included Chonburi, Thailand (curated by Nong Nooch Tropical Botanical Garden) and Angeles City, Philippines (curated by University of Guam).


Header should read:




In situ

Ex situ