An indri is built for leaping. It has very long, powerful back legs and short little arms. It cannot run on the ground very well, but it can launch itself from one tree to another and clear 10 metres in a single jump. It is one of the best jumpers of any animal in the world.
Each morning, indri families sing together. The dad and mum start, then their children join in. The song is a long, slow, eerie wail that rises and falls like a whale call. It can travel up to 3 kilometres through the forest. Other indri families hear the song and sing back from far away.
Scientists think the songs are a way of saying: this part of the forest is ours, please go around. But they also sing for joy, for family time, and to teach the babies how to make the family's song. Every group has its own slight version.
Indri have tiny stubby tails - barely there at all. Most lemurs have long tails for balance, but indri have such powerful legs that they don't need them. They mostly stay upright on the side of a tree trunk, looking very much like a furry pear with arms.