Dolphins are being strapped into tiny crates so that they can be transported by aeroplane to perform in travelling circuses where they are made to jump through hoops of fire.
Shocking footage of the animals being packaged into boxes was taken in Indonesia by campaign group Jakarta Animal Aid Network (JAAN), which is part of the Asia for Animals (AfA) network, Daily Mail reports.
Scooped out of water and strapped into a wooden container barely the size of their body, the traumatised live dolphins are loaded into the darkness of a plane's hold.
Animal lovers worldwide have been left outraged after the organisation made the footage public, and are already demanding an end to the cruel practice.
Indonesia is the last country in the world to still host travelling dolphin circuses, with three companies believed to own more 70 dolphins between them.
The creatures are plucked from the wild to ensure a miserable life of performance, which will ultimately kill them.
In the wild, dolphins can expect to live up to 50 years, while those in the circus have much shorter lifespans.
JAAN and the Dolphin Project suspect the dolphins are dying when they are as young as five-years-old, with circus owners simply replacing them with new animals when they perish.
The highly intelligent mammals often succumb to a premature end due to the stress of performance, travel and noise from crowds; their captivity and lack of social relationships; and the unsuitable pool water they are kept in.
Local activists say there are facilities available in the country to rehabilitate the dolphins and release them back into the wild.
Despite the obvious cruelty of transporting a dolphin by plane for a travelling circus, neither the airline nor the circus has broken any Indonesian laws.
Animals Asia's Animal Welfare Director Dave Neale said: "People are quite rightly outraged by the fate of dolphins in aquariums. Even the biggest pools are totally unsuitable for these animals, but what they suffer in travelling circuses is unparalleled.
"The performance pool is far too small but even this must be a welcome relief compared to how they travel. The crates the dolphins are boxed into are barely the size of their body.
"What a bewildering, stressful and horrific experience for an animal which naturally roams hundreds of miles with family and extended social group.
"Once the nightmare of air travel ends, the dolphin's only reward is to jump through hoops of fire in a tiny pool in exchange for food while surrounded by loud music. To subject dolphins to a life like this is nothing short of extreme cruelty, it is little wonder they die so terribly young."
In 2013, after pressure from animal rights campaigners, then Forestry Minister Zulkifli Hasan promised to put an end to the practice.
However, in the years since not a single dolphin has been confiscated, and campaigners are now calling on the airline to stop transporting the animals.
JAAN has called on airline Sriwijaya Air to end what the organisation describes as "its appalling business agreement with an industry built on suffering."
The group has launched a petition in an attempt to put pressure on the airline to stop transporting the creatures.
Thousands of people worldwide have put their names to the cause and have shared the petition on Facebook.
Pia Sandgren wrote: "This is so awful. Can you imagine yourself laying in a box like that and what a torture it must be? Poor poor dolphins I wish I could save them."
Joanna Smallridge said: "I just can not understand how anyone can think that this is an acceptable thing to do. What is wrong with some human beings?"
And Clare Hankey added: "So sad and so cruel. Nothing surprises me any more, don't understand how anyone can find this acceptable. Why can't these animals just be left alone in the wild?"
Mail Online has approached Sriwijaya Air for comment.