Some of the world’s most unique animals can be found on islands. Ecosystems and predator-prey relationships on islands are more closed-off than their mainland counterparts, paving the way for some distinct adaptations—think of enormous Komodo dragons, Varanus komodoensis, (indigenous to the Indonesian island of Komodo and surrounding islets) or tiny Key deer, Odocoileus virginianus clavium, (indigenous to the Florida Keys). But island life isn’t always easy and even the smallest ecosystem changes can put these animals at risk.

Here are two species that have adapted to the island lifestyle, but are now under threat due to human activity and invasive species.

Kakapo

Evolving on the islands of New Zealand with few predators and plenty of space, these birds adapted to life on land in a big way. Kakapos (Strigops habroptilus) are the only flightless species of parrot in the world—and happen to be the heaviest, too.

Without predators, kakapos safely foraged on the ground and picked fruit from trees without a need for flight. But all that changed with human settlement and introduced species such as cats, rats, and weasels. Today there are fewer than 160 kakapos left.

Solenodons

Solenodons have been on islands of their own for a very long time, both genetically and geographically. Solenodons retain primitive mammal characteristics; DNA studies indicate they diverged from other mammals about 78 million years ago. Today, there are two remaining species, each indigenous to a large Caribbean island (Cuba, Atopogale cubana, and Hispaniola, Solenodon paradoxus).

Once a dominant predator on these islands, solenodons adapted an omnivorous diet and are one of the few venomous mammals in the world. Even their venomous bite, however, has not protected them from the introduction of other predators (mongoose, dogs (Canis familiaris), cats (Felis catus)), competing foragers (rats and mice), and human development. These forces have put solenodons at risk. Both the Cuban solenodon and the Hispaniolan solenodon are currently listed as endangered species.