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Team alpha Himalayan langurs

Every Himalayan langur group has many males which aid the rest in times of need. Photo: Himani Nautiyal

Every Himalayan langur group has many males which aid the rest in times of need. Photo: Himani Nautiyal  

‘Leave no one behind’ may be the motto of male Himalayan langurs. A dog attacked a group of these primates as they walked through a field of finger millet one evening in Mandal Valley in Garhwal Himalaya, Uttarakhand. In the melee, most of the langurs raced ahead to the safety of trees while a few returned to the forest they had just left. Three adult males also made it across the field. That night was a rare occasion when the group slept in two different trees a kilometre apart, says Himani Nautiyal, who spent five years studying the species.

The three males rose well before dawn the next morning and set out to fetch the stranded members. While one waited at the edge of the forest, another stopped in the middle of the field, while the third made his way towards the isolated group. The panic-stricken langurs that had probably spent a sleepless night leaped down and followed him. The other males stood alert, keeping an eye out for danger until every member made it safely across the cropland.

Staying together

Incidents like these answered a question that had perplexed Nautiyal about the composition of Himalayan langur groups in Uttarakhand. In other species of langurs living on the plains, a single adult male typically lords over many females and young. Why would the langurs of the mountains behave so differently from their lowland cousins, allowing many males in their groups?

The terrain of Garhwal is a mosaic of forest patches and short-statured crops further bisected by fast-flowing streams. Breaks in the canopy force the tree-dwelling primates to descend to the ground, says Nautiyal, to ford streams and walk on all fours from one stretch of forest to another across farmlands. They are vulnerable to dogs, vigilant farmers protecting their farms, and other predators. A single male langur cannot safeguard his group. While entertaining rival males may not be to the alpha male’s advantage, they protect the other members of the group in times of need.

However, the young living with many adult males would ordinarily be in trouble since infanticide is common among langurs. When the alpha male deposes his rival in a typical lowland group, his first act is to kill the offspring of his erstwhile rival. If the males of these mountain primates dispatched each other’s young, no infant would be expected to survive. How does the species deal with the problem?

Plenty of food

Unlike the humid tropical forests, temperate zones have pronounced seasons, dry cold winters and wet moderate summers. Similarly, the langurs of the mountains have a defined breeding period that coincides with the time of plentiful fruits and leaves. If their young were killed, they’d be forced to give birth during inclement weather when food is scarce, which does no good for the newborn, the mother, or the group as a whole. Nautiyal says the other males prevent a new chief from going after the babies should he become aggressive. That’s perhaps the reason Himalayan langurs don’t practice gory infanticide.

Instead, the males of this species go above and beyond what other langur males do. Females focus on their newborns and cannot carry their one-year-olds as well. These youngsters scurry to keep up with the rest of the troop but often need help.

Nautiyal observed a group cross a swift stream, bounding from rock to rock. While all the adults reached the other bank, the stranded juveniles began bawling. The adult males returned and found a more accessible route for the juveniles. “They seemed to say, ‘jump here, jump there’,” she says.

Although langurs are at a disadvantage on the ground and in the open, they will not hesitate to take on dogs in the forest. When two canines caught a young langur, an adult male fought with the predators, while other males escorted the unharmed youngster to safety. A single male can’t do this, says the researcher.

Instead of bickering with each other to gain a monopoly over females, these males opt for teamwork to survive in the mountains.

The writer is not a conservationista but many creatures share her home for reasons she is yet to discover.

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Printable version | Sep 23, 2020 8:22:05 AM | https://www.thehindu.com/sci-tech/energy-and-environment/team-alpha-himalayan-langurs/article32520556.ece

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