Charles Darwin's travels through the Galapagos brought him face to face with dozens of exotic species he found profoundly beautiful ... but marine iguanas were just not one of them. The legendary naturalist described the reptiles as "the most sluggish, disgusting, clumsy lizards", taking particular note of their "horrendous sooty colour" and "hideous heads" (to which he took particular offence). He even gave them a nickname: "the imps of darkness".
The 'father of evolution' may have detested the swimming lizards, but marine biologist and Earth Touch contributor Dr Simon Pierce feels quite differently. "I get the impression that he just didn't 'get' marine iguanas like I do," he says. "I've been obsessed with them my whole life, and I'm not exactly sure why ... something to do with their amazing adaptations, the fact that they managed to survive 'rafting' over 1,000 kilometres from the South American mainland in the first place, or possibly just because they look like Godzilla."
And they do. At first glance, a marine iguana looks much like its land-loving cousin, but a closer look reveals a slew of handy adaptations for diving, like blunt noses for grazing on seaweed, muscular limbs and strong claws for clinging to rocks and flattened tails for swimming. They've even developed a perfect solution for their high-sodium diets: salt sneezing. Snacking on salty food like seaweed can be hard on the system, so special glands connected to the iguanas' nostrils allow them to expel excess sea salt, an ingenious design that can also be seen in many sea birds.
Their ability to dive up to 25 metres in search of food makes Darwin's 'imps' unlike any other reptile on earth, which made getting in the water with them particularly special for Pierce. He recalls: "Diving with the iguanas was incredibly fun – certainly one of the most entertaining dives I've ever done. Obviously I was rapt just to see them, but the hilarity value was boosted by them feeding in shallow water with a powerful surge. The iguanas have long claws to cling to the rocks. I do not. At one point [my guide] said I actually went cartwheeling past him."
Like all reptiles, marine iguanas are ectothermic, which means they need to absorb heat from their surroundings to stay warm. And though the Galapagos archipelago lies close to the equator, the waters there are surprisingly cold. That's why underwater photographers can get so close, the iguanas can't waste any time bothering to interact with them. Finding food quickly and returning to bake in the hot sun are far more important.
"The Humboldt Current sweeps up from Peru here", explains Pierce. "As it hits the islands, nutrient-rich water is forced up to the surface from depth. The rocks around the shore can reach well over 50 degrees Celsius – but the water can be over 30 degrees cooler. Iguanas are reptiles, of course, so their body temperature is regulated by the environment. When they enter the water, the clock is ticking. If they stay too long, they'll cool down to the point where they can no longer function. I got the impression that they were completely aware of me, but not particularly interested – I wasn't an obvious threat, and there was a rapidly-approaching time limit on their seaweed buffet."
If you'd like to see the iguanas (and a whole ecosystem full of incredible marine life), Pierce will be leading a photographic trip back to the Galapagos next year.
Oceans
Film and Photo
Oceans
