When a wave of Herpes B virus swept through the monkey population in Puerto Rico’s Caribbean Primate Research Center in 1979, a few hundred rhesus monkeys were shipped to an island off South Carolina’s low country and have thrived in their new home ever since.

Breeding at a rate of 750 newborns per year, the rhesus population on Morgan Island has now reached over 4,000. The monkeys have lived on this federally protected island for over three decades, and the only people allowed on the island are researchers who tag the monkeys, and take 500 per year from their home for medical testing.

Morgan Island’s rhesus population has been involved in a number of studies on vaccines, polio, AIDS and even bio-terrorism. Given the controversy around animal testing, the island is well protected, and off limits to civilians. Even those willing to break the law to get onto the island should take note that the monkeys are extremely territorial and do not react well to strangers setting foot on their island.