Monitor Lizards

Monitor lizards have a massive body and powerful legs. Most species have strong claws on their feet, and all but the largest monitors can climb well. The tail is long and powerful, usually about twice as long as the body, and can be flailed as a potent weapon. Monitors grow throughout their life, so the oldest individuals in a population are also the largest ones.

Monitors have a long, specialized tongue with a bifurcated tip that is highly sensitive to smell and taste. The tongue is extended to pick up scent chemicals, and is then retracted into the mouth where the scents are analyzed using an organ on the roof of the mouth.

Monitor lizards grow replacement teeth in the gaps between their mature teeth. They have at least 29 vertebrae above their hips. Nine of these are neck vertebrae, supporting the unusually long neck of these lizards. Their powerful jaws are hinged in the middle, allowing them to swallow large prey. The head of monitors is tapered, and there are distinct ear holes.

Monitors are active predators, hunting during the day. They stalk a wide range of animals and eat carrion and eggs as well. Monitors ingest their prey whole if it is small enough, but they can also dismember large prey items so they can be swallowed.

Monitors, like all lizards, are poikilothermic or "coldblooded." They are most energetic after they have been heated by the morning sun, since their muscles work much more efficiently and easily when they are warm. Monitors can run quickly to chase down prey. When doing so they lift their body and tail clear off the ground.

Two Komodo dragons (Varanus komodoensis). Photograph by Will & Deni McIntyre. The National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission.

Monitors also swim well, and may seek water as a refuge when threatened. They can walk underwater, and can use their tongue to smell underwater.

When threatened, monitors can be formidably aggressive animals. They can inflict painful bites and scratches, and the largest species are capable of killing a human. However, monitors can be readily tamed in captivity.