Animal testing on non-human primates between the monkeys natural behaviors versus the behaviors expressed by the diazepam induced monkeys in thirteen different locations inside the maze. Scientist Barros and his colleagues created this model to allow the monkeys to roam a less confined environment and slightly eliminate outside factors that may induce stress. Many of the best-known allegations of abuse made by animal protection or animal rights groups against animal-testing facilities involve NHPs. The so-called "pit of despair" was used in experiments conducted on rhesus macaque monkeys during the 1970s by American comparative psychologist Harry Harlow at the University of Wisconsin–Madison.<ref name="Blum1994/95">Blum, Deborah. "The Monkey
Crab-eating macaque of populations due to increased wild trade and rising levels of human-macaque conflict, which are reducing overall population levels despite the species being widely distributed. Each subspecies faces differing levels of threats, and too little information is available on some subspecies to assess their conditions. The "M. f. umbrosa" subspecies is likely of important biological significance and has been recommended as a candidate for protection in the Nicobar Islands, where its small, native population has been seriously fragmented, and is listed as vulnerable on the IUCN Red List. The Philippine long-tailed macaque ("M. f. philippensis") is listed as near threatened,