Marine iguanas are remarkable reptiles found exclusively on the remote Galapagos Islands. They are the world’s only lizards that forage in the ocean. Their distinctive appearance, characterized by dark skin and often crusted white with salt, reflects their specialized marine lifestyle.
Remarkable Adaptations for Ocean Life
Marine iguanas have specialized adaptations for their challenging marine environment. They are primarily herbivorous, feeding on marine algae, which they scrape from submerged rocks using their blunt snouts and sharp, tricuspid teeth. To manage the significant salt intake from seawater and their algal diet, they have evolved specialized salt glands located above their eyes. These glands excrete highly concentrated saline solution, expelled as a forceful “sneeze” from their nostrils.
Their flattened, paddle-like tails provide efficient propulsion through water, enabling them to dive to depths of up to 15 meters to reach their preferred red and green algae. These lizards can hold their breath for extended periods, sometimes remaining submerged for over 30 minutes during foraging dives. After cold dives, their dark skin helps them rapidly absorb solar radiation, quickly raising their body temperature while basking on volcanic rocks. Their sharp, recurved claws provide a strong grip on slippery, wave-swept rocks, preventing them from being dislodged by strong currents.
Daily Life in the Galapagos
Marine iguanas inhabit the rocky coastlines and volcanic shores, where they can easily access both the ocean for foraging and sun-warmed rocks for thermoregulation. They are highly social animals, often seen congregating in large groups, especially during periods of sunbathing. These aggregations can number in the hundreds or even thousands, creating a striking spectacle on the black lava flows. Their foraging behavior is closely tied to tidal patterns; during low tide, some individuals may graze on exposed algae in the intertidal zone, while others dive into the cooler waters at high tide to access deeper algal beds.
The breeding season for marine iguanas occurs between December and March, with nesting taking place from January to April. Females dig burrows in sandy areas or volcanic ash to lay their clutches of one to six eggs, which hatch after about 90 to 120 days. Hatchlings, measuring around 20 centimeters, emerge from the nests and immediately face the challenges of survival in their coastal habitat. While peaceful, marine iguanas share their environment with other Galapagos wildlife, such as sea lions, which often lie among them, and various seabirds like boobies that may perch nearby.
Conservation Status and Challenges
The marine iguana’s conservation status is listed as Vulnerable due to a combination of natural and human-induced threats. Natural predators include Galapagos hawks, which prey on smaller iguanas and hatchlings, and Galapagos snakes, which are known to hunt hatchlings. Introduced species pose a more significant threat to their populations. Feral cats and dogs prey on both adults and juveniles, while rats can consume iguana eggs, particularly in nesting areas.
Climate change also presents a challenge, especially through events like El Niño, which can cause significant warming of ocean waters. These warmer temperatures reduce the availability of their primary food source, marine algae, leading to starvation and population declines. Human activities, such as increasing tourism and potential pollution, also contribute to habitat disturbance and degradation. Marine iguanas are protected within the Galapagos National Park, and ongoing conservation efforts focus on managing introduced species and monitoring their populations to mitigate these varied threats.