The gregarious giant devilray tends to move around in groups, swimming close to the surface (2) (5). They apparently make long migrations (2), and show a preference for stretches of ocean traversed by strong currents (5). The giant devilray feeds on plankton and small pelagic fishes (1) (2) (5), which are strained out of the water (4). Their horn-like cephalic fins assist in feeding (5).
Giant devilrays are ovoviviparous (2), a method of reproduction in which embryos develop within eggs that remain inside the mother’s body until they hatch. The gestation period is long, lasting about 25 months, and results in only one, or rarely two, pups born in summer (2). These newborn devilrays can measure up to an astonishing 180 centimetres in width (2).