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Ladies Special: The Matrilineal World of Stump-Tailed Macaques

Things are remarkably different in this primate troop without an alpha male heading it

By RG Staff

Living in a world like ours, it’s easy to forget that females play crucial leadership roles in the animal kingdom. Take African elephants for example. Herds are commonly led by the oldest female, who mediates conflict between members and decrees how the herd will react to outside dangers. Among orcas too, older females are important members of the pod, valued for their knowledge of habitat, and their ability to find food even in the leanest of times.

Closer home, stump-tailed macaques too display matrilineal kinship. This means that they live in female-bonded social groups, where hierarchy is determined by age, and members groom, babysit, and look out for each other. Unlike male-dominated groups, stump-tailed macaques do not have a single alpha, relying instead on the leadership of a few of their oldest female members. “One might lead the troop while foraging, while another might lead in another activity,” explains Narayan Sharma, who studies the behavioural ecology of the primates of the Upper Brahmaputra Valley. “At least this is what we have observed in the Gibbon Sanctuary. It is difficult to make generalisations because the troops are so large, sometimes having over 100 members. But also because there isn’t enough research.”

Stump-tailed macaques are fascinating primates that are remarkably similar to human beings in some ways, and leagues apart in others. In India, they can be found in the northeastern states, from Assam to Arunachal Pradesh, with healthy populations living in the Hollongapar Gibbon Sanctuary, near Jorhat in Assam.

Stump-tailed macaques tend to live in troops of ten to sixty individuals (though larger ones have been observed in Hollongapar). Since they are matrilineal in nature, females remain in the group of their mother, and any female offspring they produce also remains in the troop. In effect, this means that all female members in a group are related to each other. Photo: Narayan Sharma

Males too are part of the troop, but they are not core members, and do not share the same social standing as females. Interestingly, primatologists have observed that macaques that are patrilineal in nature are far more aggressive, as males spend considerable time displaying (or maintaining) their dominant status. In the case of matrilineal kinship, dominance is granted to the eldest members, resulting in far less conflict. Photo: Udayan Borthakur

Males remain with their mother’s troop until they reach sexual maturity. At this point, they leave the group for another, therefore restricting breeding with their siblings. When males join a new group, they form their own dominance hierarchy through aggression. These displays might appear intensely combative, but primatologists say they are tame compared to other macaque species, and governed by ritual behaviour. After a fight, the subordinate presents his rump to the dominant individual, as a gesture of supplication. Following this, the aggression ceases, and normalcy is restored. Photo: Diganta Gogoi

Male aggression also comes in handy when danger approaches. Stump-tailed macaques have varied predators, ranging from dogs and leopards to large birds of prey, and it is the role of the males to protect their troop. Their main defence mechanism is to appear threatening, which they do by baring their teeth, and letting out guttural roars. Photo: Udayan Borthakur

Females are the primary caregivers of offspring, with infants receiving care from multiple females, in addition to the birth mother. The higher the social standing of the mother, the more grooming, play time, and protection the little one receives from other members. Babysitting is also a way for the younger females to gain favour with elders. Photo: Udayan Borthakur

Stump-tailed macaques are born white, with pale faces and silver hair. As they grow older, their faces gain colour, turning crimson, and eventually black. Infants are dependent on their mothers for the first nine months of life, after which they are taught to forage, climb, and protect themselves. Photo: Udayan Borthakur

Like some humans, stump-tailed macaques bald as they age. The process begins at the forehead and advances toward the back of the skull over time. Unfortunately for the macaques, this has made them desirable subjects for testing of hair regrowth. Photo: Diganta Gogoi

Foraging is a crucial skill for stump-tailed macaques and troops spend most of their day scouring the forest floor for fruit, leaves, flowers, even mushrooms. Unlike other monkeys — with long tails that help maintain balance — these primates are more comfortable at ground level, rather than up in the trees. Photo (above): Udayan Borthakur, Photo (below): Narayan Sharma

However, when the foraging is done and it’s time to call it a day, the entire troop retires to a single tree, finding nooks and crannies to rest for the night. Amid the foliage, the females groom each other, tend to their young, and eventually, fall asleep huddled with their sisters, daughters, and mothers, until the sun rises, and a new day beckons. Photo: Narayan Sharma

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