Northern muriqui

Northern muriqui are frugivorous and folivorous, but they also rely on seeds, flowers, nectar, bark, twigs, stems, vines and soil to supplement additional nutritional needs.[8][5][9] Northern muriqui consume the fruits of Margaritaria nobilis, Andira species, Anadenanthera species, Plathymenia foliolosa, Palicourea tetraphylla, Psychotria wamingii, Genipa americana and Carpotroche brasiliensis, as well as the seeds of Mabea fistulifera.[9] The amount of what each group eats depends on seasonality, wherein they will consume foods higher in calories, which results in higher fruit consumption during the wet season, and increased leaf consumption in the dry season.[10] This affect how groups of B. hypoxanthus travel as they forage for food, as bigger family groups need to travel further to attain adequate food sources. The muriqui also utilize vertical niches when foraging, as they can access all levels of forest, from the floor to the canopy. Muriqui group home ranges overlap, so unrelated groups of muriqui will avoid each other by traveling to or foraging for food by using these niche levels.[11]

Northern muriqui live in egalitarian, fission-fusion societies,[11] where the males are philopatric, and females will leave the natal group to join other muriqui groups at an average age of 6 years old before they reach puberty.[12] Male muriqui have been documented to form social cliques within their natal groups, with groups that are differentiated between older males and younger males.[13] Males display tendencies to form cooperative associations between cliques, and therefore leads to diminished intragroup conflicts compared to other species of primate. These tendencies make themselves apparent during mating season as there is little to no aggression displayed between males vying for mating opportunities, or when dealing with other natal groups of muriqui when traveling or defending their own homerange.[13] Different muriqui groups will interact with each other as group home ranges overlap.[11] During these interactions, females can enter new groups by vocalizing and interacting with new group members by hugging or touching them. Female muriquis are more independent than males; they leave their natal groups at an age of about six years.[14] Male muriquis have almost no interaction with infants. When there is an interaction between the two, the infant would be the one to initiate it.[15] Muriqui social groups are dominated by females, and males will continue to associate closely with their mothers into adulthood. It is through their mothers that adult males gain access to more females.[16]

The Northern muriqui's reproductive cycle is based on the seasonality of their environment. Infants are generally born during the dry season so that when there is a high amount of fruit production during the wet season, they can access calorie dense foods as they are weaned off of their mothers milk.[10] Females will on average be ready to mate at the age of nine, wherein they can copulate with several partners in order to conceive, however,some males can be shown preferential treatment by females.[7] Evidence points to having multiple partners in order to confuse paternity, limit male aggression, or improving odds of fertilization.[17] The gestation period for northern muriquis is a little over 7 months. The visual determination of sex can be seen within a week or so of birth, based on the shape and positioning of their genitalia.[18] There is no definitive research on the average life span of the northern muriqui, there are documented individuals reaching past the age of 30 years of age.[19]