Unlike birds and mammals, crocodilians
are unable to maintain a constant body temperature by physiological
means. For this reason they are referred to as being ectothermy.
Crocodilians have a "preferred" body temperature of around 30-33C,
and to achieve such temperatures they move back and forth between
warm and cool parts of their environment. In cold weather they bask
in the sun to heat up, and in hot weather they seek shaded, cool
areas to avoid overheating.
Basking crocodilians will usually orient themselves so that the
maximum body surface is exposed to the sun. However, as they warm,
they often face the sun, thereby reducing heat uptake by the
relatively small head, whilst the body continues to heat up. When
oriented in this way crocodilians will often open their mouths,
allowing the brain to cool through evaporative cooling, while the
rest of the body is heating. This "mouth-gaping" posture, however,
is also a behavioural display, used even at night, or when it is
raining.
Behavioural body temperature regulation limits the extent to which crocodilians
can live in cold areas. Nonetheless, it is remarkably efficient - crocodilians
can withstand prolonged periods of cool weather requiring food for temperature
regulation.
Mouth-gaping posture
Sources: G. Webb and C. Manolis (1989). “Crocodiles of Australia” (Reed Books:
Sydney);
K. Richardson, G. Webb and C. Manolis (2000). “Crocodiles: Inside and
Out” (Surrey Beatty and Sons: Sydney).
