Monitor Lizards »The Insides and Outsides Of Monitor Lizards
Nostrils
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At present little is known about the internal morphology of the nostrils (Auffenberg 1988)
but the size and position of the nostril openings reflect the range of habitats and feeding
techniques utilised by monitor lizards. The nostrils of species that spend a lot of time in water
are often equipped with flaps of skin that prevent water entering whilst the animals are
submerged (e.g. Dumeril's monitor, the mangrove monitor, the water monitor, Menens'
monitor (Mertens 1942, Krebs 1979). In species such as the water monitor and the
mangrove monitor the nares are situated towards the front of the snout, allowing the lizards
to be able to keep almost all of the head below the water and still be able to breath. In
Mertens' monitor, the openings are uniquely situated on the top of the snout rather in the
fashion of crocodilians, so that the animals can breath even when the entire head is
submerged. In other aquatic monitors (such as Dumeril's monitor and the Nile monitor) and
in many ground dwelling species (such as the Bengal monitor and Bosc's monitor) the round
openings are replaced with slits and situated closer to the eye than the tip of the snout. All of
these lizards retrieve a lot of their food from below the ground. They use their remarkable
sense of smell to detect prey and uncover it by pushing their snouts into the earth. The
narrow slit-like
opening prevents the entry of most of the debris that would otherwise
longest the nostrils. In some species this type of foraging behaviour seems to be restricted to
the older animals, and once again we see examples of major change in the transition to
adulthood. Both Bengal and Nile monitors have rounded nares as juvenile, which become
narrower as the animals age. These species spend most of their time in the comparative safety
of trees as juveniles and only seek food on the surface when they become larger. Bose's
monitor, on the other hand, roots for prey with the snout virtually from birth and the shape of
the openings does not change significantly with age.
| Attribution / Courtesy: Daniel Bennett. 1995. A Little Book of Monitor Lizards. Viper Press U.K. |
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