On today’s show we learn about the Northern River Terrapin, a critically endangered reptile native to South Asia, in the Sundarbans, in the Ganges River Delta in India and Bangladesh. Its scientific name is Batagur baska and it was first described in 1830.
Rough Transcript
Intro 00:05
Welcome to Bad at Goodbyes.
On today’s show we consider the Northern River Terrapin.
Species Information 02:05
The Northern River Terrapin is a critically endangered reptile native to South Asia, in the Sundarbans, in the Ganges River Delta in India and Bangladesh. Its scientific name is Batagur baska and it was first described in 1830.
Description
The Northern River Terrapin is one of the largest river turtles in Asia. Their carapace, that is their upper shell, can reach lengths of two feet, and they can weigh up to 40lbs. The carapace is smooth, relatively flattened, streamlined and only slightly domed, colored deep olive-green, grey, and reddish-brown. The plastron, the flat bottom shell that covers the terrapin’s underside, is pale yellow, yellow-ish orange, or creamy off-white.
Because of phrases like “a turtle carries its home on its back” and perhaps simply because of their appearance, we may think of the shell as somehow separate from the animal, but in fact it is the animal itself. The terrapin is not “inside” their shell, the shell is their body. A terrapin could no more leave their shell, than you or I could leave our spine or ribcage. The shell is living, growing bone, covered in layers of keratin called scutes. Keratin is the same protein that makes up our fingernails and toenails.
The shell grows along with the terrapin throughout their entire life; its living tissue, with blood vessels and nerves. Meaning that the terrapin can feel touch, tactile sensation on their shell. It is not just armor but also a sense organ that aids in spatial navigation. This also means that damage to the shell, scratches, cracks or punctures, can be a serious injury, causing pain and potentially leading to life-threatening infections, like a broken bone might, in our species.
Northern River Terrapin spend most of their time in the water, and so their four limbs are somewhat flattened and kind of paddle-like, adapted for swimming. The forefeet and hindfeet are webbed and clawed; webbed again for swimming, clawed for locomotion on land, for digging, and for manipulating food.
They have a short tail that is thick at the base and tapers to a tip. Their neck is long and muscular, and the terrapin can retract its neck and head to be protected by their shell. Their head is fairly small and they have an upturned snout with nostrils at the very tip, allowing them to breathe while almost entirely submerged; able to hide from predators underwater and still take in air. Oh, I should note, as a reptile they breathe surface air, into their lungs, they do not have gills.
They do not have teeth, instead their mouth is more like a serrated beak, that shears, like scissors through their mainly vegetative diet.
Their skin is thick and covered in scales that vary in size, small and fused tightly on the head, larger and more overlapping on the limbs. Their skin is generally green-ish brown, but, in the males, coloration shifts dramatically during breeding season.
Reproduction
Breeding season is December to March, during which the male Northern River Terrapin’s endocrine system produces increased levels of melanin, skin pigmentation that shifts the coloration of parts of the male’s head and neck to a deep black, and the lower parts of the neck and the forelimbs to an extraordinarily bright red-orangish- pink. And, the male’s eye color also changes, from a dark brown to bright yellowish-white.
This is called nuptial coloration, and is likely used to attract mates in the low-visibility waters of their habitat.
So, the Northern River Terrapin spends most of the year in freshwater rivers and estuaries, and then in the breeding season, make a 50-60 mile migration, downriver to the brack-ish waters and sandy beaches at the mouth of the sea, returning to the same sites year after year.
Courtship includes visual signals, like the male’s coloration; physical signals like head swaying and throat pumping; chemical signals, pheromones; and social signals like paired basking. The Northern River Terrapin is ectothermic, cold-blooded. They rely on the sun’s heat to drive their metabolism, and spend long parts of the daytime sunning, basking on banks or logs or exposed stones in large social groups. But during courtship, researchers have observed potential mates basking together in discrete pairs, as a precursor to mating.
After mating, the female will leave the water for the beach, to dig a nest in the sand, roughly a foot deep, well above the high-tide line, roughly 20 feet from the water, into which she lays a clutch of roughly 25 eggs. She then covers the nest with sand and uses her plastron, the flat bottom of her shell, to tamp down the sand and smooth it over, in hopes of camouflaging the nest from potential predators.
She then returns to the water and she and the males will begin migrating back upstream to their freshwater habitat; the young are born precocial, they do not need parental care.
So, the eggs incubate underground for roughly 2-3 months. And then as the time to hatch grows near, roughly a week before emergence, the young begin to chitchat. Making low-frequency vocalizations from within their shell: clicks, chirps, and tones, in communication with their nest-mates, their siblings. Acoustic research has found that this communication is used to coordinate synchronized hatching. All of the young break from their shells at roughly the same time. That timing is crucial because the hatchlings, each only about two inches in length, are under a foot of sand. So upon hatching, the new young collaborate in social digging: Hatchlings at the top of the group scrape sand from the ceiling of the nest, those below pack the fallen sand beneath them; digging, packing, and climbing in a group, to fresh air at the surface. This is a feat of physical exertion that would be impossible for a single individual alone.
Once above ground, they immediately move to the nearest waterway, again in a group. This behavior is called predator swamping, a kind of safety in numbers. By making a coordinated move to the water, the grouping ensures that at least some will survive possible predation (by monitor lizards or birds of prey); whereas single individuals could easily be preyed upon.
In their early life, the young remain in the brackish tidal waters of the river mouth, feeding on greens, like Water Spinach and Taro leaves; and sea vegetables; and small crustaceans. As they grow and mature they gradually make their way upstream to their freshwater habitats.
The Northern River Terrapin can take as many as 25 years to reach sexual maturity and are believed to live as long as 100 years.
In The Dream
————
In the dream,
Headed downriver, going home.
To the beach where I was born.
Cruising the river, with the downstream currents,
I know the way well, feel it deep inside me
And as the waters get salty,
I feel a lift, a lightness, a buoyancy,
Going home, I’m going home.
In the dream.
————
Habitat
The Northern River Terrapin is native to South Asia, India and Bangladesh, in the Sunderbans, at the Ganges River Delta, where the Ganges and the Brahma-putra Rivers empty into the Bay of Bengal.
The Sundarbans span the border of India and Bangladesh, and are a transitional ecosystem of tidal estuaries, tributaries, river channels and a hundred-plus islands of various size. The low-lying land is marked by salt-tolerant forests, mudflats, beaches, barrens and land converted for agriculture. It is home to the world’s largest mangrove forest which spans nearly 4000 sq miles.
This is an ecosystem shaped by the tides, which can rise and fall up to 16 feet at their springtime peak near the delta’s mouth. And can affect the river levels and salinity of the terrapin’s upstream habitat too, as the tidal effects can reach as far as 180 miles upstream from the coast. The water itself is often cloudy, muddy and brack-ish, as the rise and fall reshapes banks and beaches, reveals sandbars and mudflats, and shifts soil of clay and silt.
The climate is tropical, with seasonal monsoons. In summer, highs average in the mid-90s°F and it is hot and humid. In winter, the lows average in the mid-50s°F and it is drier and crisp, with morning mists from the Bay blanketing the delta. Then monsoon season, June to September, brings up to 60 inches of rain, roughly 85% of the region’s annual total. This inundation of freshwater has profound affect upon water salinity throughout the delta and erodes and reshapes the topography of the Sundarbans.
The Northern River Terrapin shares the Sundarbans with:
Indian Mangrove, Saltwater Crocodile, Spotted Deer, Osprey, Wild Boar, Rhesus Monkey, Sundari Mangrove, Monitor Lizard, White-bellied Sea Eagle, Brown-winged Kingfisher, Mudskipper, Fiddler Crab, Indian Beech, Smooth-coated Otter, Masked Finfoot, Brahminy Kite, Horseshoe Crab, Nipa Palm, Royal Bengal Tiger, Yellow Mangrove, Crested Serpent Eagle, and many many more.
Threats
Historically, the Northern River Terrapin was considered thriving, common and abundant in the early 1900s, but over the last 120 years, they were hunted to the brink of extinction, human predation: adults captured for their meat, eggs taken from nests for food. The terrapin return to the same nest sites each year, and move rather slowly on land, making egg theft and hunting relatively easy. By the mid 20th century, Northern River Terrapin consumption had escalated into an industrial-scale operation with tens of thousands individuals and eggs taken and exported from the Sunderbans to be sold in fishmarkets across the region. Due to this excessive overharvesting the Northern River Terrapin population collapsed and by the mid 1970s, capture and trade of the species was outlawed. But illegal poaching continued and by the late 1990s researchers believed there were less than a few dozen terrapin left.
Conservation
In 2008, a captive breeding program was established, and in 2010, at the Vienna zoo, the first Northern River Terrapin young was successfully hatched in captivity. That led to local breeding programs in both Indian and Bangladesh that also have been wildly successful. Across multiple programs, recent estimates suggest that there are over 500 individuals in captive programs. There are more Northern River Terrapin in captivity, than in the wild.
Today, a coordinated conservation plan, the Batagur Baska Vision Plan 2030, is being implemented by a partnership between West Bengal Forest Department, Turtle Survival Alliance India, and People’s Trust for Endangered Species. The program recently released 20 individuals, some tagged with radio trackers, and plans to return another 10 individuals to the Sundarbans, this spring, spring 2026.
Nevertheless the Northern River Terrapin has been considered critically endangered on the IUCN Red List since 2018 and their population is in decline.
Our most recent counts estimate that less than 100 Northern River Terrapin remain in the wild.
Citations 26:50
Information for today’s show about the Northern River Terrapin was compiled from:
Alam, Md. Shafiul, Nasrin Sultana Bristy, Mohammad Firoj Jaman, A. S. M. Morshed, Md. Shariar Rahman, Ebtesamul Haque Mim, and S. M. Mahbubul Alam. 2021. “Feeding Ecology and Growth Performance of the Critically Endangered Batagur baska in Captivity.” Herpetological Conservation and Biology 16 (2): 452–460. – https://www.herpconbio.org/contents_vol16_issue2.html
Balan Raveendran, A., Nath, A., Ahmad, A., Das, A. (2025). Conservation Strategies for Northern River Terrapin Batagur baska: Habitat Assessment and Reintroduction prospects. Global Ecology and Conservation. 62. e03763. – https://doi.org/10.1016/j.gecco.2025.e03763
Davenport, John, Tat Meng Wong, and John East. 1992. “Feeding and digestion in the omnivorous estuarine turtle Batagur baska (Gray).” Herpetological Journal 2 (4): 133–139 – https://www.thebhs.org/publications/the-herpetological-journal/volume-2-number-4-october-1992/1298-06-feeding-and-digestion-in-the-omnivorous-estuarine-turtle-batagur-baska-gray
Dedieu, A., Scherzer, N., Paumann T., Morshed A.G.J., Weissenbacher A., Walzer C., and Preininger, D. “Camera Traps Provide First Insights into the Nesting Behavior of the Critically Endangered Northern River Terrapin (Batagur baska),” Chelonian Conservation and Biology 22(1), 46-57, (14 March 2023). – https://doi.org/10.2744/CCB-1543.1
Jorgewich-Cohen, G., Wheatley, M., Gaspar, L., Praschag, P., Lubberink, N., Ming, K., Rodriguez, N. and Ferrara, C. (2024), Prehatch Calls and Coordinated Birth in Turtles. Ecology and Evolution, 14: e70410. – https://doi.org/10.1002/ece3.70410
Kumar, A., Sharma, A., Negi, N. et al. Unveiling the contemporary genetic diversity and population demography of the critically endangered northern river terrapin (Batagur baska) in the sundarbans. Molecular Biology Reports 53, 48 (2026). – https://doi.org/10.1007/s11033-025-11208-5
Mim, Ebtisamul Zannat, Mohammad Firoj Jaman, AGJ Morshed, Md Mahabub Alam, and Nasrin Akter Bristy. 2022. “Breeding Biology of Northern River Terrapin Batagur Baska in Captivity in Bangladesh”. Dhaka University Journal of Biological Sciences 31(1):67-78. – https://doi.org/10.3329/dujbs.v31i1.57917
Nawani, S., Balan Raveendran, A., Bashir, A., Kolipakam, V., Das, A., Mondol, S. (2025). Assessment of critically endangered Northern River Terrapin (Batagur baska) phylogeny through next-generation sequencing-based mitogenome analyses. bioRxiv 2025.02.03.636247. – https://doi.org/10.1101/2025.02.03.636247
People’s Trust for Endangered Species – https://ptes.org/grants/worldwide-projects/northern-river-terrapins/
Praschag, P. & Singh, S. 2019. Batagur baska. The IUCN Red List of Threatened Species 2019: e.T97358453A2788691. – https://dx.doi.org/10.2305/IUCN.UK.2019-1.RLTS.T97358453A2788691.en
Spitzweg, C., Praschag, P., DiRuzzo, S., Fritz, U. (2018). Conservation genetics of the northern river terrapin (Batagur baska) breeding project using a microsatellite marker system. Salamandra, 54(1), 63–70. – http://www.salamandra-journal.com/index.php/contents/2018-vol-54?category[0]=95
Sundarban Tiger Reserve. (2023). Annual Report 2022–23. Directorate of Forests, Government of West Bengal. – https://sundarbantigerreserve.org/web/pdf/an_report/2022_23_annual_report.pdf
Weissenbacher, A., Preininger, D., Ghosh, R., Morshed, A.G.J. and Praschag, P. (2015), Vienna Zoo & Bangladesh: Northern River Terrapin Conservation. International Zoo Yearbook. 49: 31-41. – https://doi.org/10.1111/izy.12070
Wikipedia - https://en.wikipedia.org/wiki/Northern_river_terrapin
For more information about Northern River Terrapin conservation please see the People’s Trust for Endangered Species at https://ptes.org/grants/worldwide-projects/northern-river-terrapins/
Music 28:55
Pledge 35:39
I honor the lifeforce of the Northern River Terrapin. I will commit its name to my record. I am grateful to have shared time on our planet with this being. I lament the ways in which I and my species have harmed and diminished this species. I grieve.
And so, in the name of the Northern River Terrapin I pledge to reduce my consumption. And my carbon footprint. And curb my wastefulness. I pledge to acknowledge and attempt to address the costs of my actions and inactions. And I pledge to resist the harm of plant and animal kin and their habitat, by individuals, corporations, and governments.
I forever pledge my song to the witness and memory of all life, to a broad celebration of biodiversity, and to the total liberation of all beings.
