Investigative official Akhilesh Pratap Singh told CNN that the dolphin’s carcass was found on the bank of the Sharda channel in the Pratapgarh district on Dec. 31.
On Thursday, three people allegedly seen on the video were arrested, police said. Nine people – also seen on the video – are currently still on the run, Singh said.
The video shows a group of men with sticks and an ax bludgeoning the dolphin to death. Some laughed as the dolphin’s nearly lifeless body was pulled around in the shallows by its fin.
Forest officer Varun Singh, who was part of the initial investigation, told CNN that the dolphin was an adult river dolphin in the Ganges.
The Ganges river dolphin was “once present in tens of thousands of numbers” but has now “declined dramatically” to a population of less than 1,800 in the last century, according to the World Wildlife Fund (WWF) India.
The rare freshwater dolphin is essentially blind and is known locally as ‘susu’, a reference to the sound it makes when it breathes, according to the WWF.
When hunting, the dolphin emits ultrasonic sounds that bounce off fish and other prey, allowing them to visualize an image in their heads.
According to the WWF, female river dolphins in the Ganges only give birth to one calf once every two to three years.