The Indo-Pacific finless porpoise is one of India’s smallest cetaceans, inhabits turbid coastal waters, and lacks a dorsal fin — all of which make it a difficult species for researchers to spot. Recent research suggests these animals are far more prevalent in Indian waters than visual sightings suggest, yet they may be disappearing before they can be accurately counted, reports contributor Mansab Sayyad for Mongabay India. A fully grown Indo-Pacific finless porpoise (Neophocaena phocaenoides) measures 1.5-1.9 meters (4.9-6.2 feet) in length and weighs about 30-45 kilograms (77-88 pounds). It’s highly inconspicuous: it has a blunt, rounded head, no dorsal fin, and occupies shallow, muddy waters, surfacing only briefly. But the finless porpoise can be “heard”. It navigates turbid waters by echolocation, emitting high-frequency pulses that are unique to the species and far above the range of human hearing — but detectable by specialized sound-recording devices. In 2025, a study counted finless porpoises using both visual and acoustic surveys off the Sindhudurg coast, north of Goa state. The acoustic surveys detected finless porpoises four times more often than visual surveys. Lead author Isha Bopardikar, from the Indian Institutes of Science Education and Research (IISER) Tirupati and Cornell University’s K. Lisa Yang Center for Conservation Bioacoustics, said relying on visual estimates in Indian waters is a significant drawback due to limited visibility and the animal’s brief surfacing. This means that population assessments that only use conventional visual sightings from boats may be capturing only part of the picture. Understanding the population trends…This article was originally published on Mongabay