The Rhesus Macaque is an Old World monkey found throughout Asia. The Rhesus Macaque is able to adapt to a variety of climates, from dry, extreme heat in the desert to freezing cold winters in the mountains. They can also be found living alongside humans in densely populated cities, mostly commonly in India, where they are generally left undisturbed. This promiscuous omnivore measures about 18-25 inches long with a tail adding another 10 or so inches. In addition to the invaluable contributions the Rhesus Monkey has made to medical research (Rh-factor, polio and smallpox vaccines), it was also sent into space ahead of humans.