While many lizards are known for their terrestrial or arboreal lifestyles, a remarkable subset has evolved to thrive in aquatic environments. These water-dwelling lizards showcase an array of unique adaptations, allowing them to navigate and utilize watery habitats with surprising proficiency.
Lizards Built for Water
Lizards that frequently enter water possess distinct physical and physiological characteristics aiding their aquatic movements. Many aquatic lizards feature a laterally compressed tail, which acts like a rudder or paddle for propulsion through the water. Some species also exhibit webbed feet, increasing the surface area and transforming their feet into effective paddles for swimming.
Beyond external features, specialized internal adaptations support their time in water. Certain aquatic lizards have nostrils that can seal shut, preventing water from entering their respiratory system when submerged. They can also slow their heart rate to conserve oxygen, enabling them to remain underwater for extended periods. Some marine species possess salt glands, often located near their nostrils, which filter and expel excess salt ingested from their watery surroundings, maintaining their internal balance.
Why Lizards Take to Water
Lizards utilize water for several critical reasons. A primary motivation is escaping predators; when threatened on land, many species will quickly plunge into water and swim to safety, often submerging themselves to evade detection. Water also serves as a rich hunting ground for many aquatic lizards. They prey on various aquatic organisms, including fish, insects, tadpoles, and crustaceans.
Thermoregulation is another significant factor for lizards seeking water. As cold-blooded animals, they rely on external sources to regulate their body temperature. On hot days, water offers a means to cool down, either by soaking in cooler puddles or by entering larger bodies of water. Conversely, some may use warmer water sources to raise their body temperature. Movement between habitats is also facilitated by swimming; lizards can cross rivers, streams, or other aquatic barriers to access new territories or resources.
Notable Aquatic and Semi-Aquatic Lizards
Several lizard species are particularly renowned for their aquatic prowess.
Marine Iguana
The Marine Iguana (Amblyrhynchus cristatus), found exclusively on the Galápagos Islands, is the only lizard that forages in the ocean. These iguanas dive into the relatively cold ocean waters to graze on marine algae, using their flattened tails for propulsion and sharp claws to grip underwater rocks. After their dives, their dark coloration helps them rapidly absorb heat from the sun to warm up.
Water Monitors
Water Monitors (Varanus salvator) are large, powerful lizards found across Southeast Asia, often near rivers, swamps, and mangroves. They are exceptional swimmers, using their muscular, laterally compressed tails as rudders for efficient movement, and can hold their breath for extended periods, sometimes up to 30 minutes. These opportunistic predators hunt a variety of prey in and around water, including fish, frogs, and small mammals.
Basilisk Lizards
Basilisk Lizards (Basiliscus species), native to the tropical rainforests of Central and South America, are famous for their ability to run across the surface of water for short distances, earning them the nickname “Jesus Christ lizard.” This feat is achieved by high-speed foot movements, specialized fringed toes that create a larger surface area, and rapid paddling. When they can no longer run on the surface, they are also skilled swimmers and can submerge themselves to escape predators.
Other Aquatic Tendencies
Various species of water skinks, such as the Eastern Water Skink (Eulamprus quoyii) found in eastern Australia, inhabit areas near streams and ponds. They are known to feed on aquatic insects and can quickly disappear into water when threatened. Some geckos, like the Asian house gecko, have been observed running across water, utilizing a combination of foot slap and tail undulation. Additionally, the Water Anole (Anolis aquaticus) from Costa Rica and Panama can remain submerged for up to 16 minutes by forming an air bubble on its head, which it re-breathes.