WOD2014: Marine Iguanas

This Sunday is World Oceans Day; a day that commemorates the beauty and importance of our oceans which are so integral to our survival. As can be expected for a tropical archipelago, the Galapagos Islands have an especially intimate relationship with the seas. In the run-up to World Oceans Day we shall be posting a series of daily blog articles on the marine wildlife and associated conservation projects in Galapagos. Today’s post focuses on the marine iguana.


Not many people would consider the marine iguana a pretty animal. Charles Darwin called them disgusting and clumsy, famously describing them as “imps of darkness”, but as lizards go, marine iguanas are among the most unique on the planet.

To start with, they are large; growing to 1.5 metres in length. But there is no need to be intimidated by their size, for these are herbivorous lizards. And flashy ones at that – during the breeding season, males change from their normal relatively drab grey colour to a bright display of reds and greens to attract a female.

Their real claim to fame, however, is that they are the only sea-going lizards in the world today. In order to search and graze on algae, these animals are capable of holding their breaths for more than 30 minutes and they can dive to up to 15 metres. After surfacing, they can often be seen basking on the lava rocks to warm up whilst sneezing seawater out of their nostrils; their way of getting rid of excess salt.

It may seem strange that such large creatures should have enemies, but as juveniles they face dangers from many quarters. Galapagos hawks are known to feed on small marine iguanas and the great blue heron preys on hatchlings. Non-native rats, cats and dogs have also become a threat to their eggs and young.

Another major threat to marine iguanas is El Niño; a phenomenon that sees the sea temperatures in the eastern Pacific warm by several degrees. Depending on the severity of the El Niño, several things may happen, the first of which is another incredible and unique adaptation of the marine iguana.

During an El Niño, food availability (i.e. algal abundance) decreases. It has been found that in response to this, marine iguanas release a stress hormone which causes their body to shrink by up to 20%. Research has suggested that it is not only an iguanas muscles and connective tissue that shrinks, but also their bones.

However, whilst this is an incredible adaptation, it can only help so much and in years were there is a strong El Niño, mortality in marine iguana populations can be very high. During the 1997-98 El Niño event for example, some island populations decreased by as much as 90%.

Worryingly, experts have predicted that a strong El Niño is on its way this year. In the north of the Archipelago, surface waters have already warmed by several degrees and it is highly likely that this warm front will continue southwards and engulf the whole of Galapagos to potentially devastating effect.

Whilst El Niño is a naturally occurring phenomenon, there is an increasingly large body of evidence to suggest that the frequency and intensity of events have increased as part of the change to our climate which has occurred since the industrial revolution. It is sometimes hard to imagine what impacts our activities thousands of miles away from Galapagos can have on the Islands and how we may play a part in conserving such faraway places, but if we were all to make small changes in our life to reduce our carbon footprint it really would bring about positive change to our natural world.

We have been focusing this week on World Oceans Day on Sunday, but today is in fact World Environment Day. Why not take some time to think about how you can reduce your carbon footprint for the good of the marine iguanas of Galapagos, the oceans, the environment and ultimately the future of our planet.

by Jose Hong and Pete Haskell