But Trinley Norbu, a 37-year-old truck driver, and others in the remote area on the edge of the Tibetan plateau lament that the tradition is waning, as women increasingly want a bit more commitment from a man.

The arrival of the internet, smartphones, livestreaming and popular Korean television shows, along with improved transport and education opportunities beyond the valley, have exposed the once isolated Zhaba to other lifestyles.

“Now the women especially have begun to want the same things as outsiders – fixed marriages, and financial assets such as a house or car,” he said.

But an even more dramatic challenge looms on the horizon: one of the world’s tallest dams will soon flood the Yalong valley, forcing villagers to scatter as they relocate from ancestral homes.

“It’s heartbreaking. They’ve turned our area upside down, and we don’t have any say in it,” said Trinley Norbu, who is temporarily working at the construction site.

His friend Khando Tsering stared up at the towering, unfinished support pillars of a highway that will soon halve travel times to the nearest city – and bring tourism to the once-pristine enclave.

“The economy will develop and people’s character will degenerate. Everything will be about money, and our local traditions will disappear,” he predicted.

“That’s just how things work in this era.”

Walking marriages began disappearing in the 1980s as the government imposed strict family planning measures.

The new policy meant heavy fines for babies born without legal fathers, forcing Zhaba people to obtain government marriage certificates and identify – on paper at least – a single partner as their spouse.

That process introduced the idea of “people as possessions” and caused a rise in notions of jealousy, an emotion once rarely overtly expressed, according to a paper by Qinghai Normal University anthropologist Feng Min.

Since then, walking marriage has become less and less common. Feng’s 2004 survey of 232 households found that only 49 per cent of Zhaba households still practised the tradition.

Children in such families are raised by their mother and her siblings in large, six-storey communal houses of yellowed stone on the lush green hillsides, with cavernous rooms too large for much light to penetrate.

Fathers might provide some financial support, but live with their own mothers.

“I don’t have a husband. Their father lives somewhere else,” said 60-year-old matriarch Dolma Lhamo after a breakfast of yak butter tea and tsampa, roasted flour eaten by hand, as she led two daughters out to tend the family potato field.

Shopkeeper Pema Bazhu used to share a home with her mother, grandmother, sisters and uncles, but she recently chose to move out and live separately with her husband and two-year-old son.

“It’s much more common now to see families living on their own as a unit,” she said. “It’s more convenient, and it’s better for raising children.”

Tsultrim Paldzone, 30, explained that when he and his friends were younger, they would snag tokens from girls they fancied on festival or market days, calling cards to be returned that evening during a nocturnal visit to her home.

“If she’s willing, then she’ll run just a little bit less fast. If she’s really not willing, you won’t grab that token no matter how hard you try to steal it,” he laughed.

Cars were uncommon then. He had once walked over 10km to reach one lover’s home, starting before sunset and arriving after midnight.

Now no one in the small community – just some 13,624 people according to the latest 2010 census – lives more than a half-hour’s motorbike trip away.

Trysts are arranged ahead of time on the popular cellphone messaging app WeChat, and the coy game of token-grabbing has mostly disappeared.

“There’s no challenge any more; it’s definitely not as fun as before,” the painter of temple frescoes lamented.

Government bureaucracy, too, is making it more difficult for the Zhaba’s walking marriages.

Children born to parents without marriage certificates are not allowed “hukou,” all-important registration documents that allow them to access health care and schooling.

Today, even those who wish to continue with walking marriage resort to paying unmarried acquaintances or strangers to apply for the certificate with them, said Tsultrim Paldzone.

“The government won’t let you just do as you please.”