Investigating officer Akhilesh Pratap Singh told CNN that the dolphin’s carcass was found on the Sharda canal embankment in Pratapgarh district on December 31.
On Thursday, three people who were allegedly seen in the video were arrested, police said. Nine people – seen in the video – are still on the run, according to Singh.
The video shows a group of men with sticks and an ax hitting the dolphin to death. Some laughed as the dolphin’s almost lifeless body was pulled around him by its fins in the shallow water.
Forest Officer Varun Singh, who was part of the initial investigation, told CNN that the dolphin was an adult dolphin from the Ganges River.
The Ganges dolphin was “once present in tens of thousands of numbers,” but has now “fallen abysmally” 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 noise it makes when breathing, according to WWF.
When hunting, the dolphin emits ultrasonic sounds that bounce off fish and other prey that allow them to visualize an image in their minds.
Ganges dolphins give birth to a single calf every two to three years, according to WWF.