Finless porpoises are rather shy and elusive animals (4), which do not form large schools and are most often seen in pairs consisting of a mother and calf or an adult pair (2). They generally swim quietly, rarely leaping, splashing, or riding the bow waves of boats like other small cetaceans (2). They are opportunistic feeders, consuming a variety of schooling fishes, squids, octopuses, shrimps and prawns. The finless porpoise itself is known to be preyed on by the great white shark (2).
Knowledge of reproduction in the finless porpoise currently comes only from individuals in Japanese and Chinese waters. Females are thought to calve every two years, with the peak calving season varying with location. For example, on the Pacific coast of Japan calving takes place in May and June, while it occurs in April and May in the Yangtze River (2). It is estimated that the gestation period in this species is around eleven months and that the mother feeds her calve for approximately seven months. Finless porpoises are known to reach sexual maturity at four to nine years of age and live for up to 25 years (2).