The Symphony of the Monsoon

The first heavy rains of the monsoon transform Bangladesh into a landscape of shimmering water. Rivers swell beyond their banks, inundating vast floodplains that reconnect wetlands with the surrounding landscape, while rice fields glisten beneath dark monsoon clouds. As evening descends, another transformation begins, one that often goes unnoticed. From beneath fallen leaves, muddy embankments, flooded rice fields, village ponds, marshes, and forest streams, countless frogs and toads emerge from their daytime refuges. Within moments, the quiet of the evening is replaced by an extraordinary chorus. For many people, this symphony simply announces the arrival of the rainy season. Yet few realize that they are listening to one of the country's most important wildlife communities.

Although Bangladesh covers 147,570 square kilometers [1], it possesses extraordinary ecological diversity. Located at the crossroads of the Indo-Himalayan and Indo-Burma biodiversity regions, the country supports an impressive variety of habitats [2,3].

Seasonal floodplains, rivers, haors, ponds, hill streams, evergreen forests, freshwater swamp forests, mangrove ecosystems, and agricultural landscapes collectively create ideal environments for frogs and toads. During the monsoon, many temporary pools appear across the countryside, providing breeding sites that last only a few months before drying again [4].

Floodwaters spreading across the marshes and grasslands of Tanguar Haor under monsoon cloud
Monsoon wetlands of Tanguar Haor, northeastern Bangladesh. Seasonal flooding creates an extensive network of marshes, grasslands, and shallow pools that provide critical breeding habitats for frogs and toads. Photo: Naeem Ahmod

Bangladesh is home to more than 60 known amphibian species, including tree frogs (Polypedates sp. and Chiromantis sp.), cricket frogs and paddy frogs (Minervarya sp.), skipper frogs (Euphlyctis sp.), bullfrogs (Hoplobatrachus sp.), and toads (Duttaphrynus sp.) [5,6]. While scientists continue to discover new distribution records and improve taxonomic understanding, it is clear that many regions remain insufficiently surveyed, suggesting that our knowledge of the country's amphibian diversity is still incomplete [3,7].

A Rainy Evening in Rural Bangladesh

Imagine stepping outside on a warm monsoon evening in rural Bangladesh. The rain has just subsided, and the air is filled with the earthy scent of wet soil. Rice fields shimmer under the fading light, while ponds, marshes, and temporary pools brim with fresh rainwater. As darkness falls, the countryside awakens with one of nature's most captivating spectacles, the chorus of frogs and toads.

Near village homes, the familiar Asian Common Toad (Duttaphrynus melanostictus) emerges to forage beneath streetlights and garden vegetation. A short walk toward nearby paddy fields or seasonal wetlands reveals the impressive Indian Bullfrog (Hoplobatrachus tigerinus), whose loud breeding calls echo across the landscape. Sharing these habitats is the Long-legged Cricket Frog (Minervarya syhadrensis), a small but abundant species that thrives in flooded grasslands and rice paddies.

Along the edges of ponds and shallow pools, the agile Skittering Frog (Euphlyctis cyanophlyctis) darts across the water's surface before disappearing with a splash. Meanwhile, the Bangladesh Skittering Frog (Euphlyctis adolfi) rests among floating aquatic vegetation such as Water Spinach (Ipomoea aquatica), Buffalo Spinach (Enydra fluctuans), and the elegant Pink Water Lily (Nymphaea pubescens). At the slightest disturbance, these agile frogs dart across the water's surface before disappearing beneath the vegetation. Hidden beneath damp leaf litter or among dense grasses, the diminutive Ornate Narrow-mouthed Frog (Microhyla ornata) quietly goes about its nocturnal activities, often remaining unnoticed except for its distinctive call.

The wetlands also reveal the intricate relationships that sustain these ecosystems. It is not uncommon to witness a Checkered Keelback (Fowlea piscator) seizing a Bangladesh Skittering Frog. As the snake tightens its grip, the frog may emit loud distress calls in a final attempt to escape, an evocative reminder that wetlands are shaped not only by beauty but also by the constant interactions between predators and prey.

As the night deepens, the breeding calls of frogs blend seamlessly with the persistent songs of crickets and other nocturnal insects, filling the humid monsoon air with one of Bangladesh's most distinctive natural soundscapes.

A Bangladesh Skittering Frog resting on a muddy riverbank
A Bangladesh Skittering Frog (Euphlyctis adolfi) on the bank of the Kushiyara River, northeastern Bangladesh. Photo: Naeem Ahmod

Yet these familiar species represent only a small glimpse of Bangladesh's remarkable diversity of frogs and toads. Tree frogs cling to overhanging vegetation, stream-dwelling species occupy clear forest waters, and numerous other frogs and toads emerge only under the cover of darkness. Together, they transform the rural landscape into a living orchestra, where each species contributes its own unique voice. What may sound like a single chorus to the casual listener is, in reality, a complex symphony produced by dozens of species, each playing an essential role in the health and functioning of wetland ecosystems.

Silent Workforce of Ecosystems

Frogs and toads are among nature's most effective pest controllers [8].

A single frog or toad may consume hundreds of insects in just a few nights, including mosquitoes, flies, termites, beetles, and agricultural pests. Across entire wetland ecosystems, countless frogs collectively reduce insect populations that could otherwise damage crops or spread diseases [8,9].

Their role extends far beyond pest control. Frogs and toads occupy critical positions within food webs. They serve as prey for fish, snakes, birds, monitor lizards, turtles, and numerous mammals while simultaneously regulating populations of invertebrates. The loss of these amphibians can therefore trigger cascading ecological consequences throughout an ecosystem [10].

A tree frog pressed against a lit dormitory window at night
A tree frog (Polypedates sp.) resting on the window of a dormitory in Madhupur Sal Forest, central Bangladesh. Artificial lights around forest buildings attract insects, creating feeding opportunities for frogs. Photo: Naeem Ahmod

Their dual life cycle also contributes to nutrient cycling. Tadpoles recycle organic matter within aquatic environments, while adult frogs and toads transfer nutrients between land and water, strengthening ecological connections across habitats [11-14].

Perhaps most importantly, frogs and toads are considered excellent bioindicators. Their highly permeable skin makes them exceptionally sensitive to pollution, pesticides, disease, and environmental disturbances. When these amphibian populations decline, they often provide an early warning that ecosystems are becoming unhealthy, long before humans notice visible environmental degradation [15,16].

Wetlands: The Lifeblood of Amphibians

Wetlands are far more than bodies of standing water. They are dynamic ecosystems that filter pollutants, store carbon, regulate floods, recharge groundwater, and sustain extraordinary biodiversity [17]. For frogs and toads, wetlands represent nurseries, feeding grounds, breeding habitats, and seasonal refuges [18].

Every monsoon, Bangladesh's floodplains become vast reproductive landscapes. Frogs migrate toward temporary pools where males establish calling sites and females lay gelatinous clusters of eggs. Within days, thousands of tadpoles hatch, feeding on algae and organic material before gradually transforming into adults [19].

Temporary wetlands are particularly valuable because they often lack predatory fish, increasing the survival of eggs and tadpoles. Even small roadside ponds, vernal pools, village ditches, flooded rice fields, and seasonal depressions can become essential breeding habitats [20,21].

A Rice Field Frog (Fejervarya limnocharis) with a pale vertebral stripe crouched among green grass blades
A Rice Field Frog (Fejervarya limnocharis) concealed among grasses in a freshwater wetland. Cryptic coloration provides effective camouflage against predators while the surrounding vegetation offers shelter and foraging habitat. Photo: Naeem Ahmod

The haor ecosystems of northeastern Bangladesh, freshwater swamp forests like Ratargul, the extensive wetlands of Hakaluki and Tanguar Haor, and myriad village ponds collectively form one of South Asia's most important amphibian landscapes. Protecting these wetlands therefore means protecting an entire web of life [7,22,23].

A small golden-brown frog resting on a dry leaf surrounded by green foliage
A golden-backed frog (Hylarana sp.) resting among vegetation along the bank of a freshwater beel in northeastern Bangladesh. The vegetated margins of wetlands provide essential shelter, foraging grounds, and breeding habitat for many amphibian species. Photo: Naeem Ahmod

A Kingdom Under Threat

Despite their resilience over millions of years, amphibians now face unprecedented challenges.

Rapid urbanization has replaced natural wetlands with roads, housing, and industrial infrastructure. Agricultural intensification has increased the use of pesticides and chemical fertilizers that contaminate breeding waters and reduce prey availability [24-27].

Pollution from domestic waste, plastics, and untreated industrial effluents continues to degrade freshwater ecosystems across the country. Even small concentrations of toxic chemicals can interfere with amphibian development because their permeable skin readily absorbs contaminants [26].

Climate change introduces additional uncertainty. Changes in rainfall patterns, prolonged droughts, rising temperatures, and increasingly unpredictable monsoon seasons may disrupt breeding cycles that depend upon precise environmental conditions [28].

Habitat fragmentation isolates populations, reducing genetic diversity and making local extinctions more likely. Expanding road networks create barriers that many amphibians cannot safely cross during seasonal migrations, leading to significant road mortality [29-31].

Globally, emerging infectious diseases such as chytridiomycosis (Batrachochytrium dendrobatidis) have devastated frog and toad populations. Although their impacts in Bangladesh remain insufficiently studied, strengthening disease surveillance should become an important conservation priority [32,33].

Protecting Wetlands Means Protecting Ourselves

Wetland conservation is often discussed in terms of biodiversity, but its benefits extend directly to human well-being.

Healthy wetlands reduce flooding, improve water quality, support fisheries, recharge groundwater, store carbon, and sustain agriculture. They also provide livelihoods for millions of people throughout Bangladesh [34].

When wetlands disappear, both wildlife and human communities suffer. Conserving amphibians therefore should not be viewed as protecting a single group of animals. Instead, it represents an investment in healthier ecosystems that benefit society as a whole.

Simple actions can make meaningful differences. Preserving natural ponds, restoring degraded wetlands, reducing pesticide use, improving wastewater management, supporting protected areas, promoting environmental education, and encouraging citizen science all contribute toward healthier freshwater ecosystems.

The Hidden Voices That Need Saving

Most people will never notice the remarkable diversity of frogs and toads that emerges after sunset. They remain concealed beneath leaves, hidden among reeds, or silently waiting beside streams. Yet every rainy evening, their voices remind us that healthy wetlands are alive.

A warty brown cricket frog perched on a leaf beside a brick path
A frog of the family Dicroglossidae, photographed in Sylhet, Bangladesh. Dicroglossid frogs commonly inhabit moist grasslands, agricultural fields, and urban green spaces, where they become especially active during the monsoon. Photo: Naeem Ahmod

For millions of years, amphibians have survived changing climates, shifting rivers, and evolving landscapes. Today, however, the pace of human-driven environmental change presents challenges unlike any they have confronted before.

The future of Bangladesh's wetlands, on which these extraordinary frogs and toads depend, will ultimately be determined by the choices we make today. Protecting wetlands means protecting biodiversity, strengthening ecosystem resilience, and safeguarding natural systems that sustain both wildlife and people.

References

  1. CEIC. Bangladesh BD: Surface Area. Economic Indicators. https://www.ceicdata.com/en/bangladesh/environmental-land-use-protected-areas-and-national-wealth/bd-surface-area
  2. Reza, A. A., & Hasan, M. K. 2019. Forest biodiversity and deforestation in Bangladesh: the latest update. In Forest Degradation Around the World. IntechOpen. https://doi.org/10.5772/intechopen.86242
  3. Khondker, M., Bhuiyan, M. A. H., & Bashar, M. A. 2023. Towards an appraisal of biodiversity in Bangladesh. Journal of Biodiversity Conservation and Bioresource Management 9: 79-100.
  4. Rashid, H. E. 2019. Geography of Bangladesh. Routledge, New York. https://doi.org/10.4324/9780429048098
  5. Checklist of the amphibians of Bangladesh, current as of 10 December 2012. ResearchGate. https://www.researchgate.net/figure/Checklist-of-the-amphibians-of-Bangladesh-current-as-of-10-December-2012_tbl1_320504521
  6. Freshwater Biodiversity Portal of Bangladesh. 2024. Amphibians. https://freshwaterbiodiversity.org.bd/amphibians/
  7. Ghose, A., et al. 2017. Amphibian species assemblages in a tropical forest of Bangladesh. Herpetological Journal.
  8. West, J. 2018. Importance of amphibians: a synthesis of their environmental functions, benefits to humans, and need for conservation. Honors Program Theses and Projects. https://vc.bridgew.edu/honors_proj/261
  9. Darvishnia, H. 2015. Biological survey of amphibians of Talesh Township and their biological role in pest control. Experimental Animal Biology Journal 2: 45-52.
  10. Valencia-Aguilar, A., Cortes-Gomez, A. M., & Ruiz-Agudelo, C. A. 2013. Ecosystem services provided by amphibians and reptiles in Neotropical ecosystems. International Journal of Biodiversity Science, Ecosystem Services & Management 9: 257-272.
  11. Seale, D. B. 1980. Influence of amphibian larvae on primary production, nutrient flux, and competition in a pond ecosystem. Ecology 61: 1531-1550.
  12. Hocking, D., & Babbitt, K. 2014. Amphibian contributions to ecosystem services. Herpetological Conservation and Biology. https://scholars.unh.edu/nhaes/330
  13. Wilbur, H. M. 1980. Complex life cycles. Annual Review of Ecology and Systematics 11: 67-93.
  14. Petranka, J. W. 2007. Evolution of complex life cycles of amphibians: bridging the gap between metapopulation dynamics and life history evolution. Evolutionary Ecology 21: 751-764.
  15. Sisman, T., et al. 2021. Marsh frog (Pelophylax ridibundus) as a bioindicator to assess pollution in an agricultural area. Pakistan Journal of Zoology 53: 337-349.
  16. Saber, S., Tito, W., Said, R., Mengistou, S., & Alqahtani, A. 2017. Amphibians as bioindicators of the health of some wetlands in Ethiopia. The Egyptian Journal of Hospital Medicine 66: 66-73.
  17. Sharma, L. K., & Naik, R. 2024. Wetland ecosystems. In Conservation of Saline Wetland Ecosystems: An Initiative towards UN Decade of Ecological Restoration, 3-32. Springer Nature, Singapore. https://doi.org/10.1007/978-981-97-5069-6_1
  18. Pechmann, J. H. K., Scott, D. E., Whitfield Gibbons, J., & Semlitsch, R. D. 1989. Influence of wetland hydroperiod on diversity and abundance of metamorphosing juvenile amphibians. Wetlands Ecology and Management 1.
  19. Kupferberg, S. J. 1997. The role of larval diet in anuran metamorphosis. American Zoologist 37: 146-159.
  20. Dodd, C. K., Jr., & Cade, B. S. 1998. Movement patterns and the conservation of amphibians breeding in small, temporary wetlands. Conservation Biology 12: 331-339.
  21. Calhoun, A. J. K., Walls, T. E., Stockwell, S. S., & McCollough, M. 2003. Evaluating vernal pools as a basis for conservation strategies: a Maine case study. Wetlands 23: 70-81.
  22. Fahim, Md. S. I., et al. 2025. Assessing the ecosystem health of Ratargul Freshwater Swamp Forest in Bangladesh using a modified forest quality index. Ecological Indicators 178: 113938.
  23. Afroz, T., Talucder, M., & Islam, F. 2019. Status of the fauna of Ratargul Swamp Forest.
  24. Riley, S. P. D., et al. 2005. Effects of urbanization on the distribution and abundance of amphibians and invasive species in southern California streams. Conservation Biology 19: 1894-1907.
  25. Luedtke, J. A., et al. 2023. Ongoing declines for the world's amphibians in the face of emerging threats. Nature 622: 308-314.
  26. Hayes, T. B., et al. 2006. Pesticide mixtures, endocrine disruption, and amphibian declines: are we underestimating the impact? Environmental Health Perspectives 114: 40.
  27. Bruhl, C. A., Schmidt, T., Pieper, S., & Alscher, A. 2013. Terrestrial pesticide exposure of amphibians: an underestimated cause of global decline? Scientific Reports 3: 1135.
  28. Blaustein, A. R., et al. 2010. Direct and indirect effects of climate change on amphibian populations. Diversity 2: 281-313.
  29. Lehtinen, R. M., Galatowitsch, S. M., & Tester, J. R. 1999. Consequences of habitat loss and fragmentation for wetland amphibian assemblages. Wetlands 19: 1-12.
  30. Cushman, S. A. 2006. Effects of habitat loss and fragmentation on amphibians: a review and prospectus. Biological Conservation 128: 231-240.
  31. Kolozsvary, M. B., & Swihart, R. K. 1999. Habitat fragmentation and the distribution of amphibians: patch and landscape correlates in farmland. Canadian Journal of Zoology 77: 1288-1299.
  32. Kilpatrick, A. M., Briggs, C. J., & Daszak, P. 2010. The ecology and impact of chytridiomycosis: an emerging disease of amphibians. Trends in Ecology & Evolution 25: 109-118.
  33. Berger, L., et al. 2016. History and recent progress on chytridiomycosis in amphibians. Fungal Ecology 19: 89-99.
  34. Bhowmik, S. 2022. Ecological and economic importance of wetlands and their vulnerability: a review. In Research Anthology on Ecosystem Conservation and Preserving Biodiversity, 11-27. IGI Global.