Galapagos marine iguana  (Amblyrhynchus cristatus)

Galapagos marine iguanas have evolved anti-predator behaviours towards the native Galapagos Hawk (Buteo galapagoensis) but are also threatened by introduced cats, dogs and rats. These feral animals eat iguanas and their eggs and have decimated hatchling populations in many colonies (1) (2).

This species is also sensitive to environmental fluctuations caused by El Nino (5). This natural phenomenon is caused by a failing of the trade winds resulting in an increase in sea temperature of about 4.3 degrees Celsius along with an increase in sea levels and precipitation (2). On average, El Nino occurs every 12.3 years, although the 1982 to 1983 event was the most severe for around 100 years (2). The environmental fluctuations and the following invasion of an alga (Giffordia mitchelliae) excluded the normal food species of the Galapagos marine iguana, causing the death of 50 percent of the population (8).

Oil spills and marine pollution are also very serious threats as they destroy food reserves and the nesting beaches. A recent oil spill from an Ecuadorian tanker in January 2001 spilled millions of litres of oil and fuel into the waters of the Galapagos Islands. In the following year, around 15,000 iguanas on the Island of Santa Fe alone died; over 60 percent of the entire island population. Scientists believe the oil may have killed the bacteria that the iguanas need to help digest algae, making it impossible for them to absorb nutrients (10). Fortunately, iguanas can increase their reproduction rate when population densities are low (such as after El Nino events), and thus can potentially recover from disasters to some extent (9).

The Galapagos marine iguana occurs in one of the most biodiverse areas of the world. The Galapagos Islands have long been studied and protected and were influential in the formulation of Darwin’s theory of evolution by natural selection (2). Most recently, in March 1998, a 133,000 km² area was designated as the Galapagos Marine Reserve, making it one of the world’s largest protected areas. Detailed conservation and research programmes have been developed which focus on studying the islands’ ecology, the effects of environmental fluctuations on species, and the effects of humans on wildlife (11).

Controlling introduced feral animals on the islands is the most important and urgent measure, and the Galapagos National Park and the Charles Darwin station are tackling this problem (12). Long-term conservation efforts focusing on other aspects are also essential to allow this unique species to recover (12).