Dolphin and whale records from collaborative Sea Country surveys with Indigenous Ranger groups in the Northern Territory, Australia

Context Information on cetacean distribution in coastal and offshore northern Australia is limited, constraining conservation planning. Indigenous Ranger Groups play a key role in Sea Country stewardship across the Northern Territory (NT), yet opportunities for systematic marine megafauna monitoring remain limited. Partnerships with researchers provide opportunities to strengthen local capacity, integrate Indigenous knowledge, and establish baseline data for conservation. Aims We aimed to document cetacean assemblages across NT waters and build Indigenous Ranger Group capacity in marine biodiversity data collection. Methods In partnership with nine Indigenous Ranger Groups, boat-based surveys were conducted between June 2021 and November 2023, totalling 10,342 km of survey effort. In addition, citizen science records for this period were collated and integrated into a central database. Key results Across all surveys, 112 records of eight cetacean species were documented. Four threatened, two Near Threatened and one Data Deficient species were recorded. The most frequently recorded species were the Australian humpback dolphin, Indo-Pacific bottlenose dolphin, false killer whale, Australian snubfin dolphin, and dwarf spinner dolphin. Offshore species recorded included the humpback whale, common bottlenose dolphin, and killer whale. Citizen science contributions to our study added 19 verified records of seven species including four species not recorded in our surveys, of which records of Risso’s dolphin, and the pygmy blue whale represent the first confirmed live sightings from this area. Conclusions Collaborative Sea Country surveys with Indigenous Ranger Groups substantially improved knowledge of cetacean occurrence across NT waters and confirmed the presence of several Threatened and poorly documented species. The study demonstrates the value of ongoing researcher–Ranger partnerships and citizen science in addressing major knowledge gaps in marine mammal distribution across northern Australia. Implications This research provides a foundation for conservation planning and decision-making by researchers and Indigenous Ranger Groups. However, large areas remain poorly surveyed, highlighting the need for continued monitoring and capacity building.