Harbour porpoise. A small toothed whale found mainly in cold coastal areas of the Northern Hemisphere, commonly seen in waters shallower than 200 m. It lacks a beak and has spade-shaped teeth, and primarily feeds near the seafloor on schools of small fish and squid. Usually it travels in small groups, but can form large aggregations while foraging. Its hearing is specialized for high frequencies, and it uses high-frequency echolocation clicks—an adaptation that helps against predators such as orcas. Reproduction is relatively fast with short intervals between births; it reaches maturity at a young age and typically lives for a decade or more. Although the global population is large and the IUCN lists it as Least Concern, some regional populations show serious declines.