In order to be successful newly-hatched monitor lizards must evade predators and catch
enough food to allow them to grow large enough to reproduce. On reaching sexual maturity
females must invest massive amounts of energy in egg production and select a male who will
make a good father for her offspring. Male monitors must search for females and assert their
right to mate by fighting off rivals. Once copulation is achieved the female must find or build
a nest site which will keep her eggs safe until they hatch. From egg to the grave the lizards'
behaviour is under the strict constraints of their need to thermoregulate and control water
loss, which may restrict their activity to less than half of the year.
The lifestyles of most monitor lizards are virtually unknown. The species
that have been
studied show that there are great variations in behaviour both between species and
individuals. This is not surprising considering the incredible range of sizes found amongst
monitor lizards and the wide variety of habitats that they are found in, including some of the
driest deserts and wettest forests on Earth. Whilst some species, such as the Bengal monitor,
are able to survive in many different habitats, others, such as Gray's monitor, are restricted to
a very narrow range of environmenl~. The distribution of the species also varies
tremendously. The desert monitor is found in virtually all deserts from west Africa to east
India, an area covering over 300,000,000m2
whereas the total range of the Komodo dragon,
which is found on only four small islands, is less than 2000km2
. The entire known range of
Teri's goanna amounts to less than 100km2
. (Mertens 1942, Auffenberg 1981, Irwin 1994).