Cold blood, warm river

A mugger crocodile has no internal thermostat. Every degree of its body temperature is borrowed from the world around it — and won by behaviour, not metabolism.

Crocodiles are ectotherms: they don't burn food to generate body heat the way a bird or mammal does. Instead their temperature drifts with their surroundings, and they spend much of the day actively chasing the right one — shuttling between sun and shade, bank and water, to hold their body somewhere they can actually function. Drag the dial below to watch a single mugger manage its own thermostat across one day on the Vishwamitri.

Fig. I — Thermoregulation, one riverbank

Basking

Warming on the bank

As the sun climbs, the mugger hauls out onto the mud to absorb heat directly through its dark, armoured skin — the fastest way for an ectotherm to raise its temperature.

Gaping — basking with the jaws held open — is a classic crocodilian posture, long thought to help vent heat from the head. Recent field studies suggest it may also work as a signal between nearby crocodiles, so the truth is probably both at once.

A quieter kind of heat

The temperature that decides a hatchling's sex

A mugger doesn't just feel temperature — its nest is shaped by it, months before anyone knows the eggs exist. Like most crocodilians, the mugger has no sex chromosomes. Instead, the temperature inside the nest during a critical window of incubation switches development toward male or female.

Cooler nest

→ Female

Nests in shaded or well-vegetated banks run cooler and skew female — vegetation cover measurably steadies nest temperature.

Mid-range nest

→ Male

A band of intermediate temperatures — roughly a couple of degrees wide, wider than in many other crocodilians — produces males.

Hotter nest

→ Female

Push past that middle band and development swings back to female — a female–male–female pattern documented in mugger crocodile studies.

A city with two temperatures

Vadodara's year gives the mugger two very different thermal problems: a long, punishing dry-season heat that pushes it toward water and shade rather than the open bank, and a monsoon that cools the air but floods the very banks it needs for basking and nesting. Its behaviour — where it baskets, when it gapes, which bank it nests on — is a running negotiation with a climate that never holds still.

Continue to Habitats

Climate gallery · Mugger City — thermoregulation and temperature-dependent sex determination described here follow published crocodilian field studies; exact figures vary by population and are presented as general patterns, not site-specific measurements.