Gharial (Gavialis gangeticus) Fact Sheet: Behavior & Ecology

Basking is the main activity while on land

• Amount of time spent basking is seasonal. More hours are spent basking in cooler winter months than during the hot summer, and this may occur more often on rocks than on sand.
• Typical basking pattern: Winter months -bask from 9:00 AM until 4:00 PM. Summer months -come out several hours earlier, spend 10:00 AM - 5:00 PM (hottest time of day) in the water, return for a few hours in the evening.
• Occasionally, very large animals have been observed basking at night during the hottest time of year.
• Individuals often return to the same basking spot, making them more vulnerable to predators. But they are never far from the safety of the water.

Gaping: resting with jaws wide open

• Common among basking gharials (10-20 minute periods with head raised ~20 degrees).
• At midday during the hot season, juveniles and adults remain submerged while holding heads out of water at a 20-30^o angle.

Other activities

• When not basking, time is spent in the water resting and foraging.

• Endothermic: must regulate body temperature by external means
• Bask in the sun to increase body temperature; results in better mobility and digestion
• Evaporative cooling
• Gaping: cool brain and head by
• Cool entire body by submerging under water and then lying on river bank

General

• Social group: single adult male with rostrum knob and several females
• Adult males are dominant to females and immatures.
• Size most important factor in dominance.
• Fairly social; bask in groups.

Territorial Behavior

• Adult males become territorial during the breeding season, but will tolerate small and subadult males.
• Females slightly territorial during nesting season, and will defend nest and hatchlings; females nest communally and share nesting habitat with other females.

Aggression

• Generally not aggressive towards one another, except during the breeding season.

Displays

• See Courtship

Vocalizations

• Hissing and buzzing: by males when protecting territory or during courtship. Bulbous growth on snout partially covers nostrils and sound is made during exhalation.
• Jawslap: most often under water, but occasionally above. By both males and females during courtship.
• Various types of "groans" and "bawling" have been described when animals are threatened or in pain.
• When ready to hatch, young make small grunting sounds which alerts the mother to start digging them out.

• Does not prey on people or other large mammals, but female may be aggressive when protecting her nest.
• Occasional aggressive encounters with the mugger (Crocodylus palustris) where ranges overlap. Mugger is usually the aggressor. Usually involves access to a particular basking spot.

• Unlike other crocodilians, gharials do not move well on land, and can only slide on their belly. Cannot perform terrestrial locomotion described for other species - high walk, belly run, gallop.
• They usually come out only to bask, and to prepare and tend to nest.
• Swim with limbs folded next to body to reduce drag; undulating tail provides propulsion.

Like other crocodilians, gharials often exhibit "gaping" behavior while sun basking.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Grenard (1991)
Rao & Singh (1993)
Ross (1989)
Whitaker & Basu (1982)