To understand amphibian diversity taxonomically and its threats, I have been doing fieldwork in Satchari National Park (SNP) as part of my Master's thesis program. Satchari National Park is a mixed tropical evergreen forest located at Chunarughat Upazilla of Habigonj District, Bangladesh. The SNP is about 2.43 sq. km within the Satchari Forest Range under the Raghunandan Hills Reserve Forests. The Raghunandan Hill Reserve forest borders the park on its northwestern side, while India lies to the south of the park. Tea estates, coffee and rubber plantations, and rice fields are in other areas adjacent to the park (Uddin et al., 2007). Several small, sandy-bedded streams drain the forest, enriching the forest's biodiversity. This forest is a tourist attraction as a road traverses through the woods and is convenient for travelling.
On 24th May 2022, during an amphibian survey, I searched for amphibians in a dry stream at Satchari National Park (SNP) with my supervisor Dr Shayer Mahmood Ibney Alam, and two energetic research assistants Md. Sabbir Ahmmed Shawon and Atikul Islam Mithu. At 8:16 pm that evening, while walking on a sandy dry stream where some rainwater pools were scattered randomly, we heard a loud and peculiar noise from somewhere nearby. It sounded like “ooooooong.........ooooooong........ooooooong.” We followed the sound to its source, and after some time, we noticed an Asian Painted Frog making that call in the stagnant rainwater. The frog's vivid colouration and loud vocalization reflected that it was ready to mate. We speculated that it might have chosen this place to attract a female, thus resulting in a successful amplexus. Meanwhile, we noticed similar calls from nearby locations. We observed the calls for a while and left after switching off our torch light. The following day, during the roadkill survey in the early morning, we found three dead bodies of Asian-painted frogs on the road, just a little further away from the stream we had surveyed the previous night. According to our observation, not only Asian painted frogs but also different species of amphibians were killed by vehicles every night during the monsoon season (June to October) at SNP. Many of these were female frogs of various species with eggs in their bellies.
Asian Painted Frog (Kaloula pulchra), locally known as "Venpu bang," is common, but it has a limited distribution in the northeast and southeast regions of Bangladesh (Hasan et al., 2014). Its National IUCN status is Near Threatened and is the Least Concern on a global scale (Ahasan, 2015; Kuangyang et al., 2004). The species is distributed across Bangladesh, Cambodia, China, Hong Kong, India, Indonesia, Lao, Macao, Malaysia, Myanmar, Singapore, Thailand, and Vietnam. This nocturnal frog inhabits leaf litter in forest floors and agricultural lands, including wetlands, riverbanks, wet tree holes, seasonal rain pools in the forest and forest edges, and homestead vegetation (Kuangyang et al., 2004). K. pulchra has a small head and short snout and measures up to 70mm in length. It can be easily distinguished from this species by the following characteristics: its dorsal side is chocolate-brown with yellowish-brown colour bands running the edge of the dorsal side from the snout and inter-orbital space to the back of the body. The ventral side is dark grey with numerous white spots. Pupils are round while the tympanum is absent, and the web on forelimbs is lacking, but hind limbs are poorly webbed. They can easily make burrows using truncated tips of their fingers and toes, for which it is also known as a "Digging Frog". Its body form suits walking and burrowing rather than jumping (Emerson, 1976; Soud et al., 2012). They exhibit unique characteristics when disturbed or threatened, like excreting sticky substances, the deeper colouration of the body, and inflating their body size. Activities like foraging and calling for mates begin at the first sign of heavy monsoon. This insectivore species primarily eat ants and termites (Major et al., 2017).
Snakes such as the kukri snake are predators of adult Asian Painted Frogs (Bringsøe et al. 2021), while dragonfly larvae and snails such as the golden apple snail prey upon their eggs and tadpoles (Karraker et al., 2014; Karraker, 2011). Generally, Asian-painted frogs have a lifespan of ten years (Ahsan, 2015). Unfortunately, they die before completing their entire lifespan due to unnatural deaths such as roadkill, which negatively affects their population. A road through a forest leads to habitat fragmentation, thus becoming a death trap for wild animals. Asian painted frog populations are declining daily due to the constant movement of sand-loaded trucks and unchecked speed by different vehicles travelling through the forest.
Amphibians are silent heroes of our ecosystem as they are an integral part of the food web by maintaining ecological balance. They play a vital role in indicating environmental health conditions like water quality degradation that causes several physical malformations of frogs leading to missing, malformed, or presence of extra limbs. Rapidly changing environmental factors, for example, increasing temperature and drought result in the death of frogs and tadpoles (Saber et al., 2017). Amphibian populations in Bangladesh are dwindling steadily due to anthropogenic pressure, such as habitat loss, using pesticides or herbicides in agricultural activity, construction activity, sand-filling of wetlands, and water pollution (IUCN, 2015). Roadkill is also becoming a critical factor behind their declining numbers in protected areas like the SNP. Tragically, ground-dwelling small creatures (reptiles and amphibians) are neglected more than other species in this modern world due to a lack of awareness in local communities. Policymakers are not concerned about herpetofauna before doing any infrastructure development. We are not concerned as we keep pushing them towards their population decline by carrying out activities like deforestation, urbanisation, habitat fragmentation, et cetera. I believe that now is the time to think about these small creatures that benefit our ecosystems, as knowledge about them is scarce and information about their natural history is limited. As human beings, we should respect them for their contribution to nature.
References:
Ahsan, M. F. (2015). Kaloula pulchra. In: IUCN Bangladesh. Red List of Bangladesh Volume 4: Reptiles and Amphibians. IUCN, International Union for Conservation of Nature, Bangladesh Country Office, Dhaka, Bangladesh 337, pp 234.
Bringsøe, H., Suthanthangjai, M., Suthanthangjai, W., Lodder, J. & Komanasin, N. (2021). Gruesome twosome kukri rippers: Oligodon formosanus (Günther, 1872) and O. fasciolatus (Günther, 1864) eat Kaloula pulchra Gray, 1831 either by eviscerating or swallowing whole. Herpetozoa. 34. 49-55. 10.3897/herpetozoa.34.e62688.
Emerson, S. (1976). Burrowing in frogs. Journal of Morphology. 149. Pp 437 - 458. 10.1002/jmor.1051490402.
Hasan, Md., Khan, M. M., & Feeroz, M. (2014). Amphibians and Reptiles of Bangladesh - A Field Guide 191, pp 54.
IUCN Bangladesh. (2015). Red List of Bangladesh Volume 4: Reptiles and Amphibians. IUCN, International Union for Conservation of Nature, Bangladesh Country Office, Dhaka, Bangladesh, pp. xvi+320.
Karraker, N. & Dudgeon, D. (2014). Invasive apple snails (Pomacea canaliculata) are predators of amphibians in South China. Biological Invasions. 16. 1785-1789. 10.1007/s10530-014-0640-2.
Karraker, N. (2011). Are toad tadpoles unpalatable: Evidence from the behaviour of a predatory dragonfly in South China. Amphibia-Reptilia. 32. 413-418. 10.1163/017353711X571892.
Major, T., Knierim, T., Barnes, C., Lonsdale, G., Waengsothorn, S. & Strine, C. (2017). Observations of Arboreality in a Burrowing Frog, the Banded Bullfrog, Kaloula pulchra (Amphibia: Anura: Microhylidae). Current Herpetology. 36. 148-152. 10.5358/hsj.36.148.
Kuangyang, L., Zhigang, Y., Haitao, S., Baorong, G., van Dijk, P.P., Iskandar, D., Inger, R., Dutta, S., Sengupta, S., Sarker, S.U. & Asmat, G.S.M. (2004). Kaloula pulchra (errata version published in 2016). The IUCN Red List of Threatened Species 2004: e.T57855A86163405. https://dx.doi.org/10.2305/IUCN.UK.2004.RLTS.T57855A11694615.en. Accessed on 07 October 2022.
Soud, R., Mazumdar, K., Gupta, A. & Talukdar, S. (2012). Defensive and burrowing behaviour of Kaloula assamensis and Kaloula pulchra Gray, 1831 (Microhylidae). Frog Leg. 18.
Uddin, M. & Mukul, S. (2007). Improving Forest Dependent Livelihoods through NTFPs and Home Gardens: A case study from Satchari National Park 13-35. Pp 15.
Sajib Biswas is currently pursuing his Master’s degree at the Wildlife and Biodiversity Conservation Branch, Department of Zoology, Jagannath University, Dhaka.