Smallest migrant

Copepods (subphylum Crustacea) are planktonic organisms measuring on average 1–2 mm (0.04–0.08 in) long, although some polar species might reach 1 cm (0.4 in) in length. Despite their tiny size, they are the principle diet of much of the oceans’ inhabitants – including whales. Copepods live predominantly at the bottom of the ocean to avoid predators, although make a nightly ascent to the surface to feed. This vertical migration is also considered the most massive migration.