The stump-tailed macaque has long, thick, dark brown fur covering its body, but its face and its short tail, which measures between 32 and 69 mm (1.3 and 2.7 in), are hairless.[5] Infants are born white and darken as they mature.[5] As they age, their bright pink or red faces darken to brown or nearly black and lose most of their hair.[5] Males are larger than females, measuring 51.7–65 cm (20.4–25.6 in) long and weighing 9.7–10.2 kg (21–22 lb), while females measure 48.5–58.5 cm (19.1–23.0 in) and weigh 7.5–9.1 kg (17–20 lb).[5] Males'canine teeth, which are important for establishing dominance within social groups, are more elongated than those of the females.[5] Like all macaques, this species has cheek pouches to store food for short periods of time.[5]
A study population was introduced toTanaxpillo, an uninhabited island inLake Catemaco,Veracruz,Mexico in 1974, where it ranges in seminatural conditions.[5] Most information on the species comes from the introduced population on Tanaxpillo and other captive settings, as few long-term studies have been conducted on the stump-tailed macaque in the wild.[5]
Stump-tailed macaque generally share the same social structure of any macaque species, with a linear, hereditary dominance hierarchy hereditary in females yet fluctuates among males based on their fighting ability and social maneuvering. Compared to rhesus and long-tail macaques, stump-tails defuse intense confrontations, are relatively tolerant of group members, and have a surprisingly rich repertoire of reconciliation tactics.[9] This species lacks pair bonds and is promiscuous, a staple for macaques. Physical violence very rarely occurs, and although minor scraps often flair up and physical intimidation displays occur, they tend to quickly be resolved, resulting in this species being labelled as peaceful.[citation needed] Stump-tailed macaques are remarkably unfussy in their eating habits, though fruit generally is a staple part of their diet. Stump-tail macaques have a large, bulky, muscular build with thick, solid limbs, making them very mobile on land yet quite ungainly in trees, and this unusual physique for a macaque may be responsible for this species unique tendency to consume larger quantities of meat than other macaque species. Stump-tail macaques feed on very large quantities of insects, small animals and eggs.[citation needed]
A study population of female stump-tailed macaques was found to have increased levels of steroid sex hormones, specifically 17β-estradiol and progesterone levels. 17β-estradiol levels were significantly greater during summer and fall and progesterone levels were significantly greater during summer, fall and winter. This explains how stump-tailed macaques have two mating seasons per year: one in summer (July–August) and one in fall (November). This is supported by the distribution of birth frequency in stump-tailed macaques.[10]
^Mondragón-Ceballos, R.; García-Granados, M.D.; Matamoros-Trejo, G.; Hernández-López, L.E. (2018). "Annual variations in sexual hormones and births' frequency in female stump-tailed macaques (Macaca arctoides)".Theriogenology.108:201–206.doi:10.1016/j.theriogenology.2017.11.013.PMID29227912.