Isla Genovesa, Galapagos

When I thought about coming to the Galapagos Islands, the marine iguana was the first animal I wanted to see. These lizards have always fascinated me; they are irrepressibly eccentric, doing things completely different to most other reptiles. Though their large range of unusual behaviours seems strange at first glance, they have helped them survive the unique challenges and opportunities the Galapagos presents. Marine iguanas are the only lizards in the world that feed on seaweed, swim in the ocean and memorise tide cycles.

Marine iguanas are social, eschewing the solitary lives led by most reptiles; they gather in colonies of up to 500 members, cuddling together to warm their bodies. Warmth is vitally important for these cold-blooded creatures, and although they are known as marine iguanas, they spend the vast majority of their time on land, sunbathing. The longest they can spend in the unusually cool waters of the Galapagos is about 30 minutes, before which they must sunbathe for an entire morning. After soaking up all the heat they can from the sun, the warmed-up volcanic rocks and their cuddling companions, the marine iguanas will take to the waves. This is an example of an evolutionary trade-off. The iguanas must constantly make a compromise between heating and eating, resting in the warmth until their cold-blooded bodies gain enough heat for another dive into the depths.

Their life below the waves is born out of the necessity to exploit every available food source on these islands, which has led to the marine iguanas foregoing the fruitarian diet of most other iguana species (itself already strange; lizards tend to be insectivores or carnivorous) for a menu of algae and seaweed. The iguanas can graze underwater for about an hour at a time, holding their breath all the while. This is thanks to their large lung capacity, the ability to slow their heart rate whilst underwater, meaning less oxygen consumption, and the huge quantity of red blood cells in their blood, which helps them carry a good reserve of oxygen to keep them going underwater.

The iguanas use their sharp teeth like a pair of gardeners’ secateurs to snip away the algae, using their strong claws to grip the rocks, lest the powerful underwater currents carry them away. They swim remarkably elegantly, holding their limbs to the side and using their tall, muscular, ribbon-shaped tail to propel them through the water. When they are done feeding, they climb back onto the volcanic shore and get rid of the excess salt accumulated on the swim by ‘sneezing’ - violently expelling seawater through their noses.

It’s nice to share the simple pleasures of life with these strange lizards. I sit back on the rocks, sunbathing with the colony. They don’t seem to mind my presence, and I make sure not to take the best spots. I stretch out and close my eyes, getting myself warm enough for a dip in the cold Galapagos sea.