Rabbs' fringe-limbed treefrog
This charismatic little frog may truly be the loneliest creature on Earth: only one specimen is known to exist in the world, at the Atlanta Botanical Garden in Georgia. It is the latest species to fall victim to the devastating chytrid fungus, an infectious disease of amphibians believed to be the principle reason for the sharp decline in amphibian biodiversity around the world.
The Atlanta specimen previously had a companion — a male at Zoo Atlanta — until it had to be euthanized in 2012 after its health began to fail. The last known recording of the species in the wild was in 2007. The region where it was heard later became infested with the chytrid fungus, and the frog's characteristic croaks haven't been heard since.
The Rabbs' fringe-limbed treefrog is easily recognized by its chirp, which it uses to woo females. Unfortunately for the lone male, its chimes are now forever destined to go unrequited.