The earless monitor lizard, Lanthanotus borneensis, is one of the planet’s most secretive reptiles. Native exclusively to the island of Borneo, this species is a subject of scientific fascination due to its elusive nature. It belongs to a unique family, Lanthanotidae, of which it is the only living member, and its rarity has made it a focal point for researchers.
Unique Physical Characteristics
The common name of the earless monitor lizard is a direct reference to its lack of any external ear structures. Despite this, the lizard is not deaf. It can perceive sounds by detecting low-frequency vibrations through the ground and water, an adaptation suited to its subterranean and aquatic life. This sense is complemented by a forked tongue, similar to its monitor lizard and snake relatives, which it uses to “taste” the air and ground for chemical information.
The lizard’s body is long and cylindrical, supported by short, strong limbs with sharp claws perfect for digging. Its skin is covered in rows of bumpy, keeled scales that offer protection and help it grip muddy surfaces. Its semi-prehensile tail aids in gripping as it navigates its complex environment. The lizard possesses transparent lower eyelids, a nictitating membrane that functions like built-in goggles, protecting its eyes while allowing it to see underwater or when burrowing.
Native Habitat and Behavior
The earless monitor lizard is linked to the lowland rainforests of Borneo. Its survival depends on the specific conditions found along the banks of streams, rivers, and in marshy areas. The species inhabits clear, rocky streams with a neutral pH, and can even be found in disturbed habitats like agricultural lands and palm oil plantations where streams still flow. These environments provide the necessary moisture and substrate for its lifestyle.
This reptile is primarily fossorial, spending a great deal of time hidden in underground burrows near water. These burrows, which can be up to a foot long, serve as retreats during the day. It is also a proficient swimmer and is considered semi-aquatic. Activity is largely nocturnal or crepuscular, and its diet consists of prey found within its watery habitat, including earthworms, small fish, and crustaceans like freshwater crabs.
A Living Fossil in the Modern World
Often referred to as a “living fossil,” the earless monitor lizard holds a special place in evolutionary history. It is the sole surviving species of the family Lanthanotidae, representing an ancient lineage that diverged from its closest relatives during the Cretaceous period. This uniqueness makes it a high priority for conservation, as its loss would represent the extinction of an entire reptilian family.
Due to its fragmented distribution, accurately assessing its population is challenging. The International Union for Conservation of Nature (IUCN) has listed the species as Endangered. The primary threats are habitat destruction and the illegal pet trade. Deforestation across Borneo for agriculture and development is shrinking the specific stream-side habitats it relies on.
Its rarity and unique appearance have made it a sought-after animal in the international pet trade, with individuals being sold for thousands of dollars. This demand fuels illegal poaching, impacting small, localized populations. To combat this threat, Lanthanotus borneensis is listed under Appendix I of CITES, which prohibits all international commercial trade of the species.