This chameleon of the species Calumma oshaughnessyi is only found in the mountainous rainforests of Madagascar. This makes the camouflage artist an example of numerous other reptiles, each of which is endemic to a single island. Of the 12,000 known reptile species worldwide, around a third live on islands – and almost four percent on Madagascar alone. In addition to this chameleon, such island reptiles include the Komodo dragon, the Galapagos tortoise, the tarantola geckos in Cape Verde and many species of anole lizards on the Caribbean islands. These species were able to develop because they hardly have any predators on their islands.
Their isolation makes the species unique, but also vulnerable. Because if their habitat is destroyed by human influences, the reptiles usually have no escape options or defense mechanisms. The island exotics therefore die out more easily than their mainland relatives. Around 30 percent of island reptiles are currently threatened with extinction, as a team led by Ricardo Rocha from the University of Oxford recently discovered. Across all reptiles, however, it is only twelve percent.
The tragic thing about it: The island reptiles usually fulfill important functions in their environment. “Reptiles are key species for island ecosystems. On Madeira, for example, wall lizards are ubiquitous; they hunt insects, pollinate plants and eat fruits. If the reptiles on islands disappeared, it would have a huge impact on many other species,” says Rocha. The destruction of their habitat therefore threatens the entire biodiversity and the fragile balance on the islands.
The human influencing factors include agriculture, deforestation, environmental pollution and the introduction of invasive predators – especially cats, which hunt and eat many island reptiles. “Our research in Madeira found that a single cat can eat more than 90 lizards in just one year,” said Rocha. The Madagascar chameleon, on the other hand, is threatened primarily by deforestation.
However, in order to better protect this and other island reptiles and avoid further losses, more research is urgently needed. Because these island inhabitants have so far been researched much less frequently than mainland reptiles. Since 1960, less than seven percent of all reptile studies have focused on them. This leads to the absurd situation where the islanders often die out before they have even been studied in more detail.