Crocodilians: Natural History & Conservation: Crocodiles, Caimans, Alligators, Gharials

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Mud, Glorious Mud

Adult saltwater crocodile on mud bank

An adult saltwater crocodile rests on a tidal river bank - the Adelaide River in the Northern Territory of Australia. Several metres of mud are exposed on low tide, and the crocodiles take the opportunity to bask and warm their bodies. All crocodilians are ectothermic, or poikilothermic, which essentially means that they do not generate significant body heat of their own through metabolism, but rather soak heat up from the sun. This is very advantageous for a crocodilian, which doesn't have to waste valuable energy like a mammal or bird would in order to fuel its own metabolic furnace. These energy reserves will keep a healthy crocodile such as this one well nourished for over a year without a bite to eat. The only real disadvantage of being ectothermic is that your range is limited to the warmer latitudes, although this has not tarnished the success of the modern day crocodilians at all.

Adults like this are often seen partially or even completely submerged in the sticky tidal mud. Even reptiles which need to bask can overheat, and one reason for this submergence is to help insulate the body against extreme heat during the middle of the day. Of course, there does not have to be a sound biological reason behind every behaviour, and quite often crocodiles will simply lie on the bank as the tidal runs out, becoming covered in mud in the process. Their own body weight also pulls them deeper into the mire, although with smooth belly scales, articulate limbs and a powerful tail, the crocodile can move over the mud at breakneck speed when the situation demands it: the tail swings to and fro and the crocodile almost swims through the mud into the water.