BBC Fast Track
Tourists can help at elephant camp bath time on the outskirts of Gunung Leuser National Park in northern Sumatra
They trundled over the rocky path, meandering down towards the river just after daybreak, a single file procession of majestic grey beasts linked by trunks and tails.
The seven adult elephants and two small calves play like mischievous children, spraying their handlers with water through their trunks and then falling, almost comically sideways, splashing and submerging their mammoth bodies into the cool river.
It's bath time at the elephant camp on the outskirts of Gunung Leuser National Park in northern Sumatra - and tourists are allowed to help.
The mahouts, or elephant trainers, will give you a scrubbing brush, as their grey charge lies on her side to let the ritual begin.
The skin is leathery and tough to touch, and it's a little disconcerting to be brushing with such force, yet clearly the elephants enjoy the vigorous scouring, dousing and overall attention.
But these are no ordinary elephants.
Many of the herd came from areas in Aceh where humans encroached on their land and these wild elephants often retaliated, destroying fields, houses and sometimes whole villages.
The Indonesian authorities were then forced to round up the rogues and move them to government camps.
This group of seven has been rehabilitated and trained to carry humans, and they are now instrumental in the local tourism efforts in Tangkahan.
"Our main function is to protect the National park of Leuser Mountain and the elephants play an important role in eco-tourism on our patrols twice a week," says Abdullah Hamid, an elephant mahout and an unofficial park ranger.
Fight against illegal logging
The elephants, together with their mahouts, and sometimes the odd tourist, regularly patrol the jungle around Tangkahan, in an effort to stop or deter illegal logging.
This tiny, remote village - a bumpy, three and a half hour drive from Medan - was practically built on the logging trade in the 1980s.
Elephants can go deep into the jungle on patrol for illegal loggers
But in 2001, with the help of the Indonesian NGO, Indecon, the community banded together to form the Tangkahan Tourism Institute (Lembaga Pariwisata Tangkahan (LPT) and passed regulations prohibiting the exploitation of the surrounding forest.
And so the CRU or Conservation Response Unit was born - a team of Sumatran elephants and their mahouts that helps safeguard the national park to protect it from encroachment.
"We use the elephants for the patrol because sometimes we have to go very deep into the jungle."
"Sometimes we see the illegal loggers - we cannot arrest them, but we try and educate them to conserve this forest," Hamid tells me as he prepares Eva, his 43-year-old elephant for the morning patrol.
I climb up and perch on an oversized, padded saddle on Eva's back and we begin to cross the river and into the dense rainforest on the other side.
The path is muddy and slippery beneath the lush green canopy and I'm glad I'm riding high, because down below looks like a leech wonderland.
Sumatran elephants are a lot smaller than their African relatives and they can spend up to 14 to 19 hours a day feeding.
Carmen Roberts found a sense of pride in the rural community of Tangkahan
And so our patrol is punctuated by the odd break to tear into a shrub or munch on a nearby branch.
The mahouts have also brought along fruit, for us to feed the elephants by hand.
I'm in awe at the dexterity of the trunks that can clasp a tiny chunk of pineapple from my hand and minutes later, uproot a small bush.
At times the terrain is quite steep, I'm hanging on for dear life, and yet I'm amazed at how nimble and deceptively light-footed these large creatures seem to be as we traverse ravines and gullies with ease.
As we arrive back to the elephant camp, there's a small crowd of local villagers gathering for lunch.
A group of barefoot children beg their parents for a ride, and the mahouts are obliging, even though they aren't paying visitors.
"The community gets a lot of benefit from these elephants and their work, it allows them to make money from eco-tourism and it encourages the villagers not to take wood from the forest," Hamid explains.
Tangkahan is referred to as a hidden paradise in Sumatra, but what makes it different is that it's an example of how grass roots eco-tourism efforts can help stop illegal logging and instill a sense of pride in a community.
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