Chained-up monkeys in south-east Asia could be picking the coconuts used to make the various trendy brands of water and oil sold in health food stores and supermarkets across the world.

Baby monkeys are stolen away from their mothers, who are often shot by hunters, and sent to special schools where they are taught to pick as many as 1,000 coconuts a day.

Many of the coconut-based products, which have become the must-have for healthy eaters and celebrities alike, are sourced from Thailand where the majority of coconuts are picked by these cruelly-treated animals, reports claim.

Several major brands that MailOnline investigated source their products from Thailand, as well as the south-east Asian nations of Indonesia and the Philippines.

These coconut oils and waters have been espoused by several celebrities who blog about their health benefits and use them as nutritious alternatives in their 'free-from' bakes.

And nearly every supermarket or grocery store now features coconut water, making the whole industry worth around a billion pounds.

But as demand grows, so does the abuse of macaque monkeys who suffer 'serious psychological damage' as a result of being chained up 24-hours-a-day.

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Training regime: A monkey named Dam (pictured) lifts weights made from coconuts at the Phuket Monkey School in Laem Sai, Thailand

Hard day's work: The monkey's are chained up by their necks and forced to pick as many as 1,000 coconuts a day

Cruelty: Chained-up monkeys (pictured in Thailand) in south-east Asia could be picking the coconuts used to make fashionable health products such as coconut water and oil

Aggressive: Animal charity Wild Futures has told MailOnline that chaining the animals and forcing them to do menial tasks all day long damages their mental state

Hard labour: Monkeys are abducted from their mothers as babies, and taken to special schools (pictured in Thailand) where they are chained up and trained to pick coconuts

Harmful: The monkeys are shown off to tourists as amusing attractions, but being chained up for up to eight-hours-a-day causes the socially intelligent creatures serious damage, animal charities claim

Many coconut water companies source their product south-east Asian countries like Indonesia, where 18m tonnes of coconuts are harvested every year, and Thailand, which produces just over one million tonnes annually.

It is unknown how many of the coconuts used to make the products are picked by monkeys.

But the Bangkok Post claims that if the drink sourced from Thailand, the coconuts were 'most likely' picked by monkeys.

Some monkeys are known to work from 8am to 5pm and only stop for a short break on rainy days and Sundays.

When they are not working, their owners place a muzzle on their faces and shackle them to a tree stump or a shed - restricting their movement and interaction with other monkeys.

A well-trained monkey can pick hundreds more coconuts than a human, who are limited to a few hundred at most, and fetch up to £1,200 when sold to other farmers.

Chained up: Monkeys are forced to work from 8am to 5pm and are shackled even when they are not working

Efficient: Well-trained monkeys (pictured in Indonesia) can pick up to 1,000 coconuts a day while a human can pick a few hundred at most

Trained: Monkeys are taught to spin the coconut with both hands and feet to dislodge the coconut quickly

Cruel process: The monkey's handler hold the rope (left), which is tied to a chain around its neck, as it climbs the tree and throws coconuts down (right)

Manual labour: Footage shows a monkey scaling a tree to collect coconuts before his owner yanks the chain around his neck - signalling him to come back down

Collection: Some monkeys are even trained to collect coconuts from the ground and place them in bags, which saves their owners hours of back-breaking labour

Footage from a monkey training school in Koh Phangan, Thailand, shows a monkey expertly scaling a tree, removing a coconut and throwing it back down - all within 30 seconds.

Once it has emptied the tree, the monkey's handler yanks the chain tied around the its neck to make it climb back down.

These monkeys are shown off to tourists as amusing spectacles by their owners who claim the animals enjoy climbing and picking fruit.

But chaining them up the socially-intelligent creatures, and forcing them to carry out menial tasks, causes 'lasting psychological damage', Claire Turnbull of the Wild Futures monkey sanctuary told MailOnline.

HOW MONKEYS ARE TRAINED TO PICK 1,000 COCONUTS A DAY The First Monkey School in Surat Thani, Thailand, describes how it turns wild monkeys into coconut-harvesting employees on its website. It says the monkey should be comfortable in its surroundings, even though the images and video on the website show the animal chained up. The monkeys are first taught how to rotate coconuts - which helps loosen them from trees. A trainer starts by turning the coconut which has been placed on a pole and soon, the monkey will become 'curious' and want to copy them. Once it has learned how to rotate the coconut with its hands and feet, the trainer will simulate a real situation by hanging it from a bamboo rod decorated with some coconut leaves. No rest: When they are not working (pictured), their owners place a muzzle on their faces and shackle them to a tree stump or a shed The website says the monkey 'will never climb into a coconut tree without a line' - which is tethered around its neck - so it must learn to free itself should that line become stuck. This is method takes between three and six months to teach and costs £108. Some monkeys then qualify for 'secondary school' where they are taught to pick coconuts and put them in a bag, which they will carry to any place the owner wants. This takes another six months and costs the owner £450. The highest level of education offered in this establishment is called 'high school', where they teach the monkey to do 'practically everything the owner wants'. Advertisement

She said: 'By keeping them socially isolated, on chains or in small cages, monkeys can develop a host of abnormal behaviours which range from "extreme submission" to self-harming behaviour.

'As they mature, primates naturally become aggressive. In order to keep them submissive, primates are typically subjected to abusive training methods which make them anxious and fearful.

'We absolutely urge companies to make sure they source fruit from farms that do not exploit monkeys in this way.'

Monkey schools claim training places emphasis on showing the macaques kindness and never punishing them for mistakes.

Working monkey: A macaque rides on the back of a pickup truck with its owner at a coconut plantation in Chumphon province, southern Thailand

Commodity: Well-trained coconut pickers can fetch up to £1,200 when sold to other farmers

False industry: Monkeys are shown off to tourists as amusing spectacles by their owners who claim the animals enjoy climbing and picking fruit

The monkeys are taught how to free themselves from become entangled in ropes and even how to select ripe fruit.

According to the Bangkok Post, one training centre claims that using pig-tailed macaques is safer than using humans because they are 'strong, enjoy climbing, do not complain, do not call for higher wages... and are not corrupt.'

It adds: 'They do not require social security and accident insurance. Monkeys are therefore considered a "living machine" that is very valuable for coconut farmers.'

Some monkeys are even taught to collect grounded coconuts and put them into sacks, which saves their owners hours of back-breaking labour.

Locals in Thailand argue that monkeys have been helping their 'human friends' harvest coconuts for hundreds of years.