Pesut

Pesut, the Indonesian name for the Irrawaddy dolphin (Orcaella brevirostris), is a small to medium-sized toothed whale that inhabits brackish and coastal waters. In Indonesia, the pesut is best known from the Mahakam River in East Kalimantan, where long-term observations have documented its presence and behavior.

Taxonomy and description: Orcaella brevirostris belongs to the family Delphinidae. Pesut have a robust, fusiform body, a rounded forehead, a short beak, and a small, triangular dorsal fin. They are gray to brown with a lighter ventral side.

Habitat and distribution: They live in estuaries, river mouths, and shallow coastal zones. In Southeast Asia they are found in brackish waters of river systems and near coasts; the Mahakam River hosts a notable population, while other regional populations exist in coastal and riverine habitats.

Behavior and diet: Pesut are social, usually occurring in small groups. They surface to breathe and often feed on small fish and crustaceans, foraging in shallow channels and near river mouths. They are known to interact with boats but can retreat when disturbed.

Reproduction: Sexual maturity is reached after several years. Gestation lasts about 10-12 months, and calves stay with their mothers for 2-3 years. Population growth is slow, contributing to vulnerability.

Conservation: The IUCN lists the Irrawaddy dolphin as Endangered. Main threats include bycatch in gillnets, habitat loss and pollution, and disturbance from boats and coastal development. Conservation actions focus on protected areas, bycatch reduction, community-based management, and ongoing research and monitoring, particularly in the Mahakam River.