Marine Iguana

Amblyrhynchus cristatus

Reptile

Transcript:

Today on Animal Fact Files we’re discussing marine iguanas. These animals are special because they're the only living marine lizards. A marine iguana's body is shaped to facilitate their more aquatic lifestyle. They have a compressed tail for swimming which helps propel them through the water. It's similar to how an eel swims, which is exactly how Charles Darwin described them during his observations in the Galapagos Islands. Marine iguanas also have a flat nose which makes gathering food from hard surfaces easier. They don't need a pointed snout for holding onto wriggling prey. These lizards also have long claws for holding tight to rocks and other hard surfaces while they eat. The waves can't push them around! Marine iguanas also have a dark body which helps them warm up more quickly after diving in cold water. These ocean reptiles range from 2 to 5 feet (60-150 cm) in length on average– and that's including their tail. However, it's important to note these amazing vertebrates are able to shrink during inclement weather. And not just their weight, they can reduce their entire body size!!

Marine iguanas are endemic to the Galapagos Islands; they're only found in this small section of the world. There are different subspecies spread across separate islands, but all of these separate groups are currently considered the same species. The water around the Galapagos Islands is usually cold which promotes an annual growth of red and green algae that prefers cold water. This is the marine iguana’s main source of food, however, warm weather events, such as El Nino, as well as global warming threaten the lizards’ lifestyle. Marine iguanas have adapted to the El Nino events over time, they can shrink their size, not just weight but also length, even reabsorbing their own bones to do so. When they shrink, they need less energy to survive, so lack of food is less of a problem. What's more, they can do this process multiple times throughout their life, adjusting as the weather goes through its natural changes. Unfortunately, global warming is a greater, more permanent threat from which these reptiles cannot shrink away.

Marine iguanas also face threats in the form of introduced predators not native to the islands. Cats, dogs, rats, and pigs all destroy marine iguana populations when left unchecked. Generally speaking, these reptiles have few natural predators, although herons and hawks prey on both adult marine iguanas and their eggs. On their side of the food chain, marine iguanas are the only living lizards to enter seawater to eat. They almost exclusively eat green and red algae when it's available. These lizards dive up to 16 feet (5 m) on average, but ventures to depths of 50 feet (15 m) is not wholly uncommon for these resourceful reptiles. A marine iguana's dives are typically no more than a few minutes long, but excursions over 30 minutes have been observed. The water they dive in is rough with strong waves, so they have to hold tight to the rocks and hard surfaces the algae grows on– thankfully their long, strong claws help facilitate this. Juvenile marine iguanas have it a bit easier as they go to intertidal zones to eat during low tide– obviously the adults don’t want to compete with their own children, so they eat elsewhere.

Marine iguanas are ectotherms meaning they get their heat from the surrounding environment, so they have to warm up by using the sun’s rays. A dive into the cold waters around the islands can greatly impact their body temperature to the point that they become so cold they're lethargic. When they’re too cold, they’ll act really aggressive as a bluff to scare potential threats away. These lizards are often seen basking and sneezing. They blast salt out of their nose after ingesting seawater. The salt encrusts on their head giving their head a lighter appearance than the rest of the body. Marine iguanas also change color during the mating season and the different subspecies change different colors. Some are bright red, others turn green– the algae they eat may play a role in the color change.

Male marine iguanas are territorial over a harem of females. They’ll fight over territory disputes, but these matches are not usually deadly. It's more like pushing and headbutting matches. The mating season peaks from December to March and nests are most abundant from January to April. Marine iguana nests are made on land in the sand. After she's laid her eggs, the female stays for a few days to keep watch of her offspring, but eventually leaves and the eggs incubate for 3-4 months. The babies hatch and must run, often on two legs, to find cover before they're attacked by predators. Female marine iguanas start mating around 3 to 5 years of age and males take nearly double that as they must gain dominance over the rest of the males in the area. The average lifespan for a marine iguana is about 10 years, but some can live more than double this if they can avoid threats.

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