Limbani the chimpanzee was rejected by his mother as a baby because he had pneumonia.
Scientists estimate there are only 2,500 great green macaw parrots left on the entire planet.
Scientists use drones to track the population of the endangered green turtles.
This will be the seventh pygmy marmoset at Vienna Zoo, which aims to protect the vulnerable species.
Diego, who is more than 100 years old, is widely credited with saving his species from the brink of extinction.