Thursday, June 26, 2014

Encountering a Wild Lace Monitor

When we began our trek to the beach at Cape Tribulation in Queensland, Australia, we hoped to see wildlife among the exotic foliage. Butterflies were varied and numerous. A chorus of forest birds called out all around us. 

In the dim forest light, spotting this rufous night heron (Nycticorax caledonicus) was exciting. This was the wildlife we expected. Amazing how similar it was in appearance and behavior to the black-crowned night heron we frequently see in the Los Angeles area.

But our thrill came when a rustle in the mangrove leaves revealed a 5-foot-long lace monitor (Varanus varius). Monitor lizards are primarily predators, hunting birds, small mammals and other reptiles. Some species also eat insects and crustaceans. The lace monitor is the second largest monitor species in Australia, and Australia is the land of lizards. In a country where most of the marsupial predators have become extinct, monitors are important mesopredators (predators of small prey).

Southern California's equivalent mesopredators would be the gray fox, island fox, coyote, bobcat, and red-tailed hawk. Predators are much fewer in an ecosystem than prey species, making the sighting of one an unexpected pleasure. However, like our mesopredators, lace monitors are adaptable and with the decrease or extinction of large predators, mesopredator populations increase. The more resourceful species can sometimes get in trouble frequenting campgrounds and picnic areas, or even cities, where people create an opportunity for food. While this lace monitor might scavenge in the near-by park, we watched it exhibiting natural behaviors–using its forked tongue and Jacobson's organ to sense for food and other monitors. Watch the Video at

Monitor lizards have a deeply forked tongue like a snake and a keen chemosensory ability. As solitary creatures, they use this sense to communicate with others of their species. We watched this lace monitor mark its territory by rubbing glands, on the head and near the cloaca, on a tree trunk. Another lace monitor traveling this trail would be able to tell the gender, size, and probable health and mating status of this monitor from its scent marking. 

This behavior is very similar to that of wild felines, which also mark territory with chemical scents. (Your cat is actually marking you as its territory when it rubs its cheeks against your leg. Watch the lace monitor video and see if it doesn't remind you of your cat.) In Australia and Indonesia where there are no wild feline species, monitors are large lizards that fill the same niche. They are able predators, moving rapidly, tracking prey, climbing trees, and living in a variety of habitats.

In North America, our largest lizards are fairly small (under 2 ft or 70 cm, snout to tail tip) and the second largest, the chuckwalla is primarily herbivorous. There is no niche for a large predatory lizard because we have wild felines, bobcats, mountain lions, lynx, and the occasional ocelot or jaguar. I've only seen local bobcats on rare occasion and only felt the watching eyes of a mountain lion. Seeing this lace monitor was a reminder of the importance of predators in a healthy ecosystem and how special it is to see a mesopredator in the wild, especially when you are just taking a walk to the beach.

Cape Tribulation, Queensland, Australia

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