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Two Gandak River Turtle Species Used Main Channel and Pebbly Tributaries Differently

Indian flapshell turtle (Lissemys punctata) with yellow spotting, photographed in Haryana, India
Research · Ecology

A study published in 2026 found clear habitat partitioning between Indian flapshell turtles (Lissemys punctata) and Indian roofed turtles (Pangshura tecta) in the Gandak River system in northern India. Indian roofed turtles were found only in smaller, pebble-dominated tributaries, while Indian flapshell turtles occurred at all four study sites and were encountered more often in the main river channel.

Encounter rate describes how often turtles were found during standardised survey effort. A higher winter rate therefore means the researchers encountered the species more frequently under winter survey conditions; it is not by itself evidence that the total population was larger in winter.

Researchers surveyed the sites across seasons while measuring hydrological and physicochemical conditions. They recorded 69 turtles in total: 43 Indian flapshell turtles and 26 Indian roofed turtles. Morphometric measurements were also used to examine length–weight relationships and body condition.

Winter conditions favoured both turtle species

Encounter rates for both species peaked in winter and were associated with stable, clear-water conditions characterised by greater transparency and higher pH together with lower temperature and flow. No turtles were captured or observed during the peak monsoon, when hydrological disturbance was highest.

The length–weight relationship was negatively allometric in both species: body mass increased less rapidly than expected if shape and proportions remained geometrically similar as the turtles grew. Condition factors indicated that body weights were generally consistent with the fitted length–weight relationships. The authors conclude that maintaining habitat heterogeneity and natural flow regimes is important for conserving the two turtles in the Gandak River system.

Sources and image credit

  1. Sharnappa, M. H., Singh, D. P., Kumari, R., Dutt, D., & Singh, M. K. (2026). Habitat partitioning and environmental drivers of two turtles (Lissemys punctata and Pangshura tecta) in a transboundary Himalayan river Gandak, India. Environmental Monitoring and Assessment, 198, 181. https://doi.org/10.1007/s10661-026-15035-4Primary research article first published online 28 January 2026. Seasonal surveys at four sites in the Gandak River recorded 43 Lissemys punctata and 26 Pangshura tecta. Pangshura tecta was confined to smaller pebble-dominated tributaries, while Lissemys punctata occurred at all sites and was encountered more often in the main channel. Encounter rates for both species peaked in winter; neither species was captured or observed during peak monsoon.

Image: CLpramod — Indian flapshell turtle (Lissemys punctata), photographed 26 February 2017 at 28.470360° N, 76.810493° E in Haryana, India. The Wikimedia Commons description identifies the visible yellow spots and blotches as characteristic of the nominate form L. p. punctata. Original work by the photographer; Wikimedia Commons; CC BY-SA 4.0. Representative species image, not a turtle from the Gandak River study. · CC BY-SA 4.0 · Source

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