Extinction watch: A jaw-dropping, colour changing Boa

Among all terrestrial vertebrates on Earth, this is the only species that has an intramaxilliary joint that can separate and split the anterior and posterior bones of the upper jaw.

It is believed that this helps the snake to hold on to its preferred meal of geckos and skinks.

Once prevalent all over Mauritius, the introduction of pigs and rodents led to a huge population decline and animal grazing destroyed its habitat. Now this boa is found only on Round Island.


This group of snakes are not actually true boas, and diverged from all other snakes more than 65 million years ago. That is before the extinction of the dinosaurs!

Another distinction of this species is its specialised skin cells that allow individuals to change colour over a 24-hour period.

They darken during the day, when they are inactive, and are lighter at night when they are more active. Unlike true boas that give birth to live young, the Round Island boa lays eggs. There may be fewer than 500 individuals left in the wild which is why it is listed as endangered in the IUCN list.

Round Island is a protected area and visitors to the island are restricted to scientists and conservationists.

The Durrell Conservation Trust, along with the Mauritian Wildlife Foundation, has led a restoration programme for the snake, removing all introduced goats and rabbits from Round Island and reintroducing native plants, allowing the natural habitat to regenerate.

This conservation work has also helped the lizards of Round Island recover, leading to increased prey availability and therefore population growth for the boa, too.