Lace Monitor

Overview

The Lace Monitor (Varanus varius), frequently celebrated colloquially across Australia as the ‘tree goanna,’ is a massive, highly agile monitor lizard that reigns as the second-largest lizard on the Australian continent, surpassed in size only by the desert-dwelling Perentie. Belonging to the family Varanidae, this formidable predator represents an ancient Gondwanan evolutionary lineage that has dominated Australasia’s terrestrial ecosystems since the Miocene epoch. Ranging across eastern Australia from the tropical forests of northern Queensland down to the temperate woodlands of Victoria and South Australia, the lace monitor occupies a dominant niche as both an arboreal ambush hunter and an indispensable terrestrial scavenger.

Renowned for its intricate, lace-like patterning of cream, yellow, and black scales, the lace monitor is an astonishingly proficient tree climber despite its formidable bulk, easily ascending towering eucalypts using razor-sharp, recurved claws. Alongside its impressive physical dimensions—often exceeding six feet in total length—the species possesses specialized venom-secreting oral glands that induce hypotension, rapid shock, and impaired blood clotting in captured prey. Functioning as a primary cleaner of the Australian bush through its insatiable consumption of carrion, the lace monitor is an iconic wildlife symbol deeply embedded in Indigenous Australian Dreamtime mythologies and modern herpetology.

Biology and Physical Characteristics

Varanus varius possesses an exceptionally powerful, muscled anatomy tailored for both terrestrial sprinting and vertical arboreal climbing. Its elongated, laterally compressed torso is supported by robust limbs terminating in five long, powerful digits armed with massive, laterally flattened, curved claws that act as climbing crampons, digging into thick eucalypt bark with ease. The tail is extraordinarily long—measuring roughly 1.5 times the length of the head and body—and is laterally compressed with a sharp dorsal keel; this appendage functions as a dynamic counterbalance when running along horizontal tree boughs and as a defensive whip capable of delivering stinging strikes against predators.

The cranial anatomy of the lace monitor is optimized for macroeconomic predatory consumption. The jaws are equipped with backwards-curving, laterally compressed teeth with finely serrated edges that shear flesh and clamp down on struggling prey. Advanced biochemical research has confirmed that, like other varanid lizards, the lace monitor possesses complex mandibular venom glands located within the lower jaw; this venom contains proteins that cause rapid blood pressure collapse, muscle paralysis, and profuse hemorrhaging, ensuring that even large prey items that escape the initial bite rapidly succumb to shock. The senses are dominated by a long, deeply forked, blue-black tongue that flicks continually in and out of the mouth, transferring microscopic scent particles to the Jacobson’s (vomeronasal) organ in the roof of the mouth, enabling the lizard to detect rotting carcasses or buried reptile eggs from miles away.

Behavior and Ecology

Lace monitors are active, diurnal hunters that divide their time between patrolling the forest floor for carrion and scaling the high forest canopy in search of nesting birds, gliders, and possums. Foraging involves slow, systematic searching with the head held low and the forked tongue constantly sampling the air and substrate. When hunting terrestrial animals like rabbits or lizards, the monitor can unleash astonishing bursts of speed, sprinting on all four legs with an undulating gait. When threatened by terrestrial predators such as dingoes or introduced foxes, the monitor immediately dashes for the nearest vertical tree trunk, spiraling around the opposite side of the trunk as it climbs to keep the solid wood between itself and the threat.

Reproduction showcases one of the most remarkable mutualisms in the reptile kingdom. Breeding occurs in late spring and early summer, accompanied by dramatic ritualized wrestling matches between rival males who stand upright on their hind legs and tail bases in a ‘bear-hug’ grapple to assert dominance. Following mating, the gravid female locates an active, arboreal or terrestrial termite mound (typically built by Nasutitermes species). Using her powerful claws, she excavates a deep tunnel into the center of the mound and deposits a clutch of six to nineteen leathery white eggs. The industrious termites promptly repair the breach, sealing the eggs inside a natural, climate-controlled incubator that maintains constant temperature and high humidity throughout a lengthy nine-month incubation. When the hatchlings emerge the following spring, the mother frequently returns to dig open the rock-hard mound, assisting her offspring into the world.

Conservation and Human Impact

The Lace Monitor is currently assessed as Least Concern on the IUCN Red List of Threatened Species, maintaining widespread and relatively stable populations throughout its historical range across eastern Australia. Its status as an opportunistic generalist capable of exploiting both native wildlife and introduced pest species (such as European rabbits and roadkill) has allowed it to persist in landscapes where more specialized predators have declined.

Nonetheless, lace monitors face localized population stresses in developing regions. Extensive agricultural land clearing and commercial forestry remove the mature, hollow-bearing eucalyptus trees and large termite mounds strictly required for shelter, basking, and egg incubation. High vehicular road mortality is also prevalent, as the lizards are drawn to warm asphalt roadways to feed on roadkill carcasses, frequently falling victim to oncoming traffic. Furthermore, poison ingestion from eating toxic introduced cane toads (Rhinella marina) in northern Queensland has caused localized population crashes, though southern populations remain unexposed. Conservation efforts emphasize preserving old-growth woodland remnants, installing wildlife warning signs across critical road-crossing corridors, and legally protecting all native varanids under state and federal environmental legislation.

Interesting Factoid

Female lace monitors use live termite colonies as natural baby incubators: they tear open active termite mounds to lay their eggs, and after the termites cement the hole shut with rock-hard pulp, the eggs incubate in perfect humidity and temperature for nearly nine months until the mother actually returns to dig her newly hatched babies out.