Natural History Hooded seals are generally regarded as solitary in nature, except during moulting and mating.
Hooded seals are sexually dimorphic with males being larger than females.
Male hooded seals also have a black, crescent shaped, inflatable nasal sac that when flacid droops down over the muzzle. With one nostril closed, male hooded seals can also inflate their nasal septum through the opposite nostril, producing a large red balloon-like structure. Both are used in courtship and dominance displays. Females lack these secondary sexual characteristics. Females give birth to one pup yearly on pack ice, away from the edges of ice floes.