Brazil’s Araguaian river dolphins (Inia araguaiaensis) are normally hard to find and study. But researchers from the University of Vermont and University of St. Andrews came cross them near a fish market in the town of Mocajuba, where shoppers often feed them. The researchers shot rare video footage of the dolphins which also managed to capture a number of vocalizations. Clicking sounds are used for echolocation. Midway through the video, a young dolphin makes a short, two-part call as it approaches its mother, causing bubbles to escape its blowhole as it produces the sound. The dolphin was thought to be quiet and solitary, but the biologists found they can make hundreds of different sounds — a finding they believe could help uncover how communication evolved in marine mammals.