<P> In Central and South America forest fragmentation and hunting are the two main problems for primates . Large tracts of forest are now rare in Central America . This increases the amount of forest vulnerable to edge effects such as farmland encroachment, lower levels of humidity and a change in plant life . Movement restriction results in a greater amount of inbreeding, which can cause deleterious effects leading to a population bottleneck, whereby a significant percentage of the population is lost . </P> <P> There are 21 critically endangered primates, 7 of which have remained on the IUCN's "The World's 25 Most Endangered Primates" list since the year 2000: the silky sifaka, Delacour's langur, the white - headed langur, the gray - shanked douc, the Tonkin snub - nosed monkey, the Cross River gorilla and the Sumatran orangutan . Miss Waldron's red colobus was recently declared extinct when no trace of the subspecies could be found from 1993 to 1999 . A few hunters have found and killed individuals since then, but the subspecies' prospects remain bleak . </P>

Monkeys found mostly in africa that tend to be more omnivorous and are both arboreal and terrestrial