Diving behaviour of a critically endangered crocodilian: ecological drivers and conservation implications

Abstract

This study explores the diving behaviour of the critically endangered gharial (Gavialis gangeticus) to understand how
these airbreathing aquatic reptiles utilise river depth for foraging, avoidance to disturbance, thermoregulation and energy
conservation. Four captive-bred adult gharials (1 M:3 F; body lengths 345–384 cm) were introduced into the Mahanadi
River, India, and radio-tracked for an average of 114 ± 53.5 days using Argos-enabled FASTGPSDIVE transmitters. These
devices recorded key parameters, including dive depth, duration, submergence time, and dive intervals, across spatial and
temporal scales. The average dive depth was 2.56 ± 2.20 m with shallow dives (0.75–1.75 m) occurring most frequently
(52.67%). Deep dives (> 10 m) were rare (0.3%) but notable. Dive frequency peaked between 0600 and 1200 h, while dive
depth and duration were highest in winter, with maximum values of 12.75 m and 34 min, respectively. Larger individuals
tended to dive deeper, and gharials in disturbed areas (outside the Protected Area (PA)) exhibited greater dive depths than
those within (inside PA). Submergence time was higher at night (24%) than during the day (20%) (MWT, p < 0.006). The
interval between dives was longest during the rainy season (85.90 ± 2.27 min) and shortest in winter (61.97 ± 1.39 min)
(KWT, p < 0.001). This research has broad implications, particularly for understanding the minimum ecological flow
requirement in the river to sustain the critically endangered gharials, at a time when increasing infrastructure development
and climate change have affected river ecosystems. We acknowledge the limitations of a very small sample size and
recommend interpreting the results with caution when planning conservation measures.

Keywords:
Gharial, Mahanadi river, Animal behaviour, GPS telemetry, Crocodile conservation, River ecology

Publication Date
February 2026

PUBLICATION AVAILABLE AT:

Diving behaviour of a critically endangered crocodilian: ecological drivers and conservation implications | European Journal of Wildlife Research | Springer Nature Link