two common types of monitor lizards

all along i had thought that the monitor lizards that i have encountered during my nature walks actually belonged to the same species. i have come across monitor lizards, usually of a smaller size, during my walks at forested areas and the larger ones are usually found in the water or near the water edge at mangrove swamps or water bodies.

i only realise that there are two common types of monitor lizards - the water monitor lizard and the clouded monitor lizard - when i saw an information board, similar to this, at the lower peirce reservoir boardwalk.

the two species of monitor lizard are similar in appearance. those found in forested area, away from the water, have yellow spots on a brown-grey base. they are usually smaller in size. the one distinguishing difference is that the nostrils of the clouded lizard lie midway between the eye and the snout; whereas, in the case of the water monitor lizard, the nostrils lie near the tip of the snout.

incidentally, while searching for more information on the two species, i came across this very informative nature blog with very good pictures.

do they reduce their number?

i have sometimes wondered how they keep the number of wandering monitor lizards at the sungei buloh wetland reserve under control. in one of many walks at the reserve, i thought i stumbled upon the answer. i had accidentally wandered off the beaten track when i came across many metal cages set up to catch these enormous lizards.

the diet of monitor lizards includes carrion - dead and rotting meat. to trap these monster lizards, they leave parts of a dead chicken hanging from a hook in these huge rectangular cages. one trap was so huge, it could be used to trap adult crocodiles. the trap works like a rat trap. when the monitor lizard gets into the cage and tugs at the piece of chicken, it will dislodge a rod, which in turn will cause the mouth of the trap to snap shut.

i had wandered off the designated track when i came upon more than 10 of these cages or traps, of varying sizes, laid out over a one kilometre stretch. some still had the bait hanging in the cages but some did not have any thing inside - no bait and no captured animal. in fact, i did not come across any trapped animal.

from what i have gathered, this is part of a research programme held in collaboration with the national institute of education (nie). when the reptile was captured, they would first syringe some blood from it. the lizard would be put to sleep with a lethal injection. in the laboratory, they would dissect the big lizard to study the content in its gut.

on the topic of catching monitor lizards, my friend nah once told me that the foreign workers, especially the thais, used a simple loop to trap the monitor lizards that lived on the banks of the kallang river. they would set up the trap overnight and collect their booty the next morning. the thai workers did not catch the monitor lizards to keep as pets. i have been told that the meat of the lizard tastes better than chicken's meat.

another friend of mine, who served as a camp instructor on pulau tekong some 30 years ago, claimed that the taste was akin to that of chicken meat. one of the islanders would trap the lizard and cook it himself. he added some herbs were used to get rid of the fishy taste.

a former student of mine told me that commandos in the army were trained to capture and have the meat of the monitor lizard as part of their jungle survival diet.