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<p>This study explores the diving behaviour of the critically endangered gharial (<i>Gavialis gangeticus</i>) 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&#xa0;M:3&#xa0;F; body lengths 345–384&#xa0;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&#xa0;m with shallow dives (0.75–1.75&#xa0;m) occurring most frequently (52.67%). Deep dives (&gt; 10&#xa0;m) were rare (0.3%) but notable. Dive frequency peaked between 0600 and 1200&#xa0;h, while dive depth and duration were highest in winter, with maximum values of 12.75&#xa0;m and 34&#xa0;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, <i>p</i> &lt; 0.006). The interval between dives was longest during the rainy season (85.90 ± 2.27&#xa0;min) and shortest in winter (61.97 ± 1.39&#xa0;min) (KWT, <i>p</i> &lt; 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.</p>

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

  • 期刊论文

  • 发表日期：

    2026年2月5日

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  • Laxmi Prasad Rath,
  • Rajesh Kumar Mohapatra,
  • Suraj Kumar Dash,
  • Ashaharraza Khan,
  • Sanath Kumar N.,
  • Manoj V. Nair,
  • Sudarsan Maharana

摘要

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.