Marine Mammal Reporting Records Along the Tamil Nadu Coast, India: A Five- Year Baseline for Wildlife Surveillance and Conservation

The ocean is vast and often hidden from view, making it difficult to know exactly what lives beneath the surface or what happens when those creatures face trouble. For scientists who study marine mammals—animals like dolphins, whales, and dugongs that breathe air but live in the sea—understanding their health and where they go is a constant challenge. These animals act as sentinels for the ocean; because they live long lives and sit high up in the food chain, their health often reflects the overall condition of the marine environment. When they become sick, injured, or die and wash up on shore, these events are not just sad occurrences but valuable clues. By carefully recording these sightings and strandings, researchers can learn about which species are present, what threats they face, and how to protect them. This kind of monitoring is especially critical in places where systematic, year-round scientific surveys are rare, turning every report from a fisherman or a forest ranger into a vital piece of a larger puzzle.

In the southeastern coast of India, the state of Tamil Nadu stretches along the Bay of Bengal and the Indian Ocean, hosting a rich variety of marine life. To understand the status of marine mammals in this region, a team of researchers from the Tamil Nadu Forest Department conducted a comprehensive review of official records kept over a five-year period, from 2020 to 2024. They gathered every report of a marine mammal sighting or a dead animal found on the beach that had been logged by the department. This collection included 250 separate reports, which represented 343 individual animals. The team did not go out to sea to count animals themselves; instead, they analyzed the existing data to see what the current system was capturing, how well it was working, and what gaps remained in their knowledge.

The records revealed a diverse group of animals, though many were difficult to identify precisely. Among the 343 individuals documented, the dugong, a large, gentle sea cow that feeds on seagrass, was the most frequently recorded species, with 104 individuals spotted or found dead. Following the dugongs were various types of dolphins and porpoises, including the Indo-Pacific finless porpoise and the humpback dolphin. The researchers also noted rarer visitors, such as a blue whale, a humpback whale, and a pilot whale. However, a significant portion of the data remained vague. More than half of the reports, specifically 135 out of 250, did not identify the animal beyond a general category like "unidentified dolphin" or "unidentified whale." This lack of specific identification limits the ability of scientists to understand the exact needs and risks facing different species, as each type of dolphin or whale may have different habitats and conservation requirements.

The location of these reports told a clear story about where the animals were being found and where the reporting network was strongest. The vast majority of the records, 167 out of 250, came from the Ramanathapuram Forest Division. This area covers the Gulf of Mannar and Palk Bay, regions known for their rich seagrass meadows and coral reefs, which are critical habitats for dugongs. While this concentration suggests that many animals are indeed present there, the researchers noted that it also reflects where the reporting effort is highest. Other coastal divisions reported far fewer events, with some recording only a handful of sightings over the entire five years. This uneven distribution highlights that the data is influenced by how many people are watching the coast and how quickly they can report what they see, rather than just the actual number of animals in the water.

Time played a role in the reporting as well, though not in a predictable seasonal pattern. Reports came in throughout every month of the year, with no single season dominating the data. The number of reports fluctuated from year to year, peaking in 2022 with 72 records and dipping in 2021 with 28. This variation suggests that the frequency of reports is likely tied to factors like weather, human activity on the coast, or the availability of observers, rather than a strict biological cycle of the animals themselves. The sources of these reports were also diverse, coming from a mix of forest department staff, local residents, and fishermen. This collaborative network shows that the community is actively engaged in watching the coast, with forest personnel accounting for the largest share of reports, followed closely by local residents.

When it came to understanding why animals died, the data was often incomplete. Of the 207 reports involving dead animals, only 47 included a specific diagnosis or a clear explanation of the cause of death. For the remaining 160 cases, the cause of death was unknown. Among the few cases where a cause was identified, injuries from trauma were the most common, followed by signs of illness such as pneumonia. This gap in diagnostic information is a significant hurdle. Without knowing whether an animal died from a fishing net, a disease, or natural causes, it is difficult for conservationists to design effective protection strategies. The researchers found that while post-mortem examinations were performed on many carcasses, the results were not always recorded or were inconclusive due to the condition of the animal when it was found.

The study concludes that while the current reporting system in Tamil Nadu has successfully built a valuable baseline of information, it needs strengthening to become a truly powerful tool for conservation. The existing records prove that a network of observers is in place and that a wide variety of marine mammals frequent these waters. However, to move from simply counting events to understanding the health of the population, the system requires more standardized methods. The researchers suggest that better training for field staff to identify species, improved protocols for examining dead animals, and a more consistent way of recording data would greatly increase the scientific value of these reports. By refining these processes, the state can transform its collection of reports into a robust surveillance program capable of detecting emerging threats and guiding the protection of these vital marine species.