This is the call of a tree hyrax, a small, furry mammal that looks like a cross between a groundhog and a ground squirrel—minus the bushy tail. John Oates: The most characteristic sound of the majority of tree hyrax populations is loud, repetitive shrieking or screaming cry that you only hear at night, which reverberates through the forest. Bender: Each species of tree hyrax has its own unique call: due to their distinctive shrieks, Oates and an international team of researchers discovered a new species of the mammal. They live in those rocks.” Well, tree hyraxes are supposed to sleep in trees. Oates: There’s a lot more to this thing than just this poor little rabbit or marmot or groundhoglike animal that makes strange noises in the middle of the night.