Yucatan spider monkey
Ateles geoffroyi yucatanensis

The Yucatan spider monkey (Ateles geoffroyi yucatanensis ), also known by its mayan name "Ma'ax", is a disputed subspecies of Geoffroy's spider monkey, and is one of the largest types of New World monkey. It inhabits Mexico, Guatemala and Belize. It is a social animal, living in groups of 20-42 members.

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The subspecies is no longer recognised by the International Union for Conservation of Nature (IUCN) or the Integrated Taxonomic Information System (ITIS), it is listed as a junior synonym of the Mexican spider monkey (Ateles geoffroyi vellerosus ).

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The Yucatan spider monkey weighs around 9 kg, making it one of the largest of the New World monkeys. It has long arms and a prehensile tail, which can support its own weight. The body is long and slender and covered with black hair, which is coarse and often looks matted. Adult body length ranges between 305 to 630mm, with a 635 to 840mm long tail. They live in large fruit trees and jump from branch to branch effortlessly moving up to 40 feet in one swing, causing them to be a great seed disperser for many tree species. The fur is somewhat paler than that of the Mexican spider monkey. There are usually tan-coloured markings around the eyes and chin, and whiskers around the head area.


Habits and Lifestyle

The Yucatan spider monkey is very social, living in groups of anywhere between 10 and 100 members (20-42 members on average). These groups are typically dominated by females, one of whom plans foraging routes for the rest of the group.

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Male-male relationship have also been documented. In these there is a focus on physical behaviour such as grooming, embracing, arm-wrapping, and grappling. Though most of these actions are reciprocated between the two males, the most successful bonds tend to be between males of similar ages, with pronounced differences in male-male relationships with a larger age gap (between individuals of <10 years and ≥ 14 years). Actions performed between males of similar ages showed that the affection was beneficial for both of the monkeys, while in the relationships with larger age differences, a lot more affection was given by the younger male than was received, possibly showing the value of respect of elders in groups.

The Yucatan spider monkey find the tallest trees for better protection from predators and access to fruits. They feed primarily during the early morning and rest for the remainder of the day. When threatened, these monkeys will "bark" while throwing objects including feces or branches while jumping up and down.

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Diet and Nutrition

The Yucatan monkey is frugivorous, with a diet consisting of around 90% fruit and 10% eggs and insects. In captivity, the Yucatan spider monkey’s diet generally consists of fruits, dog food, bread and a few vegetables, such as carrots and lettuce. Wild Yucatan spider monkeys favor wild figs called "koochlé", the fruits of ramón, and other wild tamarind fruits.

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The Yucatan spider monkey moves in straight lines towards its food, and is able to orient its movement to foraging areas invisible from its current vantage point. Individuals consistently plan out foraging areas ahead of time.

Foraging behaviour after a natural disaster (a hurricane) showed increased splitting up into smaller sub-groups. Less time was spent moving, and the main food source changed from fruit to leaves.

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Mating Habits

Yucatan spider monkeys reach an average age of 25 years in wild, while in captivity this is closer to 35 years. A female Yucatan spider monkey ovulation is suppressed by lactation and birth occurs once every 2 to 3 years. Females have an estrous cycle of 24 to 27 days. Mating is a period of two to three days. They have a long gestation period of 226-232 days. Males are sexually mature in five years and females in four.

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The infant monkey is completely black, and will cling to its mother’s back for the first two years of its life. It will also only start eating fruit at around two years old. The males have no role in offspring carrying.

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The Yucatan spider monkey is classified as Endangered by the IUCN due to ongoing rapid population decline (totalling well over 5-% over three generations) caused by continued habitat loss and fragmentation, pet trade and severe hunting pressure. Deforestation related to illegal drug trade rates are 20-60% per year.

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1. Yucatan spider monkey Wikipedia article - https://en.wikipedia.org/wiki/Yucatan_spider_monkey
2. Yucatan spider monkey on The IUCN Red List site - https://www.iucnredlist.org/species/160872795/17979441

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