Wednesday, May 25, 2011

Komodo Dragon Habitat Komodo Island

A deer nimbly picks its way down a path meandering through tall savanna grasses. It is an adult male of its species, Cervus timorensis, weighing some 90 kilograms (about 200 pounds). Also known as a Rusa deer, the animal knows this route well; many deer use it frequently as they move about in search of food. This Rusa's home is the Indonesian island of Komodo, a small link in a chain of islands separating the Flores Sea from the Indian Ocean. Most wildlife find survival a struggle, but for the deer on Komodo, and on a few of the nearby islands, nature is indeed quite red in tooth and claw. This deer is about to encounter a dragon.

The Komodo dragon, as befits any creature evoking a mythological beast, has many names. It is also the Komodo monitor, being a member of the monitor lizard family, Varanidae, which today has but one genus, Varanus. Residents of the island of Komodo may call it the ora. Among some on Komodo and the islands of Rinca and Flores, it is buaja darat (land crocodile), a name that is descriptive but inaccurate; monitors are not crocodilians. Others call it biawak raksasa (giant monitor), which is quite correct; it ranks as the largest of the monitor lizards, a necessary logical consequence of its standing as the biggest lizard of any kind now living on the earth. (A monitor of New Guinea, Varanus salvadorii, also known as the Papua monitor, may be longer than the lengthiest Komodo dragons. The former's lithe body and lengthy tail, however, leave it short of the thickset, powerful dragon in any reasonable assessment of size.) Within the scientific community, the dragon is Varanus komodoensis. And most everyone also calls it simply the Komodo.

Komodo Dragon

The Komodo's Way of Life

The deer has wandered within a few meters of a robust male Komodo, about 2.5 meters (eight feet) long and weighing 45 kilograms. The first question usually asked about Komodos is, how big do they get? The largest verified specimen reached a length of 3.13 meters and was purported to weigh 166 kilograms, which may have included a substantial amount of undigested food. More typical weights for the largest wild dragons are about 70 kilograms; captives are often overfed. Although the Komodo can run briefly at speeds up to 20 kilometers per hour, its hunting strategy is based on stealth and power. It has spent hours in this spot, waiting for a deer, boar, goat or anything sizable and nutritious.

Monitors can see objects as far away as 300 meters, so vision does play a role in hunting, especially as their eyes are better at picking up movement than at discerning stationary objects. Their retinas possess only cones, so they may be able to distinguish color but have poor vision in dim light. Today the tall grass obscures
the deer.

Komodo Dragon

Should the deer make enough noise the Komodo may hear it, despite a mention in the scientific paper first reporting its existence that dragons appeared to be deaf. Later research revealed this belief to be false, although the animal does hear only in a restricted range, probably between about 400 and 2,000 hertz.
(Humans hear frequencies between 20 and 20,000 hertz.) This limitation stems from varanids having but a single bone, the stapes, for transferring vibrations from the tympanic membrane to the cochlea, the structure responsible for sound perception in the inner ear. Mammals have two other bones working with the stapes to amplify sound and transmit vibrations accurately.

In addition, the varanid cochlea, though the most advanced among lizards, contains far fewer receptor cells than the mammalian version. The result is an animal that is insentient to such sounds as a low-pitched voice or a high-pitched scream.

The Komodo makes its presence known when it is about one meter from its intended victim. The quick movement of its feet sounds like a "muffled machine gun," according to Walter Auffenberg, who has contributed more to our knowledge of Komodos than any other researcher. Auffenberg, a herpetologist at the University of Florida, lived in the field for almost a year starting in 1969 and returned for briefer study periods in 1971 and again in 1972. He summed up the bold, bloody and resolute nature of the Komodo assault by saying, "When these animals decide to attack, there's nothing that can stop them." That is, there is nothing that can stop them from their attempt--most predator attacks worldwide are unsuccessful. The difficulties in observing large predators in dense vegetation turn some quantitative records into best estimates, but it is informative that one Komodo followed by Auffenberg for 81 days had only two verified kills, with no evidence for the number of unsuccessful attempts


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