The Strange World of Troglobites | 20 Years of Planet Earth | BBC Earth (Level 1)

Some animals live deep inside dark caves. They never go outside and never see the sun. These animals are called cave specialists. Caves are like lonely islands. Because these animals live in the dark for a very long time, they look very strange. They do not have colors on their skin. They do not even have eyes. It takes many years for animals to lose their eyes. But they have other ways to live. For example, the blind salamander feels small movements in the water to find food. The cave angelfish holds onto rocks in fast water and eats tiny bacteria. Food is very hard to find in a cave. Some animals wait many months to eat. When food finally comes, they must catch it quickly. It is amazing that these strange animals can live in such dark places.