褐吼猴是巴西及阿根廷大西洋沿岸森林的特有種。2016年因黃熱病爆發，導致牠們的數量下降了86.6%而成為瀕危。巴西政府與保育團體組織了一項計劃，與圈養設施及專家合作，將吼猴野放到其數量已經消失或減少的地區。為對抗黃熱病，科學家亦成功地將原為人類開發的黃熱病疫苗改造給吼猴。
Brown howler monkey is endemic to the Atlantic forest in Brazil and Argentina. They became endangered after a yellow fever outbreak in 2016, which resulted in a 86.6% decline in their population. Brazilian government organized a program with conservation organizations to work with captive facilities with experts to release howler monkeys to areas where their population have vanished or declined. To fight the yellow fever, scientists successfully adapted the yellow fever vaccine that was developed for human use to a vaccine to howler monkeys.
