The generic name Cystophora means "bladder-bearer" in Greek, from the species' unusual sexual ornament – a peculiar inflatable bladder septum on the head of the adult male.

Sexual dimorphism is obvious from birth and females are much smaller: 2.03 meters (6 ft 8 in) long and weighing 145–300 kg (320–661 lb).

Hooded seals live primarily on drifting pack ice and in deep water in the Arctic Ocean and North Atlantic.

They can be found on four distinct areas with pack ice: near Jan Mayen Island (northeast of Iceland); off Labrador and northeastern Newfoundland; the Gulf of St. Lawrence; and the Davis Strait (off midwestern Greenland).

[8] Hooded seals are known to be a highly migratory species that often wander long distances, as far west as Alaska and as far south as the Canary Islands and Guadeloupe.

From January 1997 to December 1999, a total of 84 recorded sightings of hooded seals occurred in the Gulf of Maine, one in France and one in Portugal.

[9][10] The diet of the hooded seal is composed primarily of various amphipods (crustaceans), euphausiids (krill), and fish, including Atlantic argentine, capelin, Greenland halibut, cod, herring, and redfish.

[12] Hooded seals tend to feed in relatively deep waters ranging from 100–600 m (330–1,970 ft), and dive from 5 to 25 minute durations.

The purpose of this happening is for acoustic signaling, meaning that it occurs when the seal feels threatened and attempts to ward off hostile species when competing for resources such as food and shelter.

[15] In sexually mature males, a pinkish balloon-like nasal membrane comes out of the left nostril to further aid it in attracting a mate.

[17] There are four major breeding areas for the hooded seal: the Gulf of St. Lawrence; the "Front" east of Newfoundland; Davis Strait (between Greenland and northern Canada); and the West Ice near Jan Mayen.

The NE herd whelping (giving birth) around Jan Mayen generally disperse into the sea after they breed in March.

They are born with a slate blue-grey coat (giving them the name "blueback"), with a pale cream color on the belly, which they will molt after about 14 months.

Studies show that cardiac blood flow provides sufficient oxygen to sustain lipolytic pathways during dives, remedying their hypoxic challenge.

This is due to the large stores of oxygen, either bound to hemoglobin or myoglobin, which the seals rely on to dive for extended periods of time.

[26] Studies have shown that newborn hooded seals undergo a stage after birth where the thickness of their blubber grows rapidly, which maximizes their ability to thermoregulate and compensate for their thin fur coat.

The first test on each subject yielded differing results, ranging from reduced diving activity and rapid exploratory swimming.

[26] Conservation practices, brought about by international cooperation and the formation of the Northwest Atlantic Fisheries Organization (NAFO) led to hooded seal population increases.