to 250 meters. Male harbour seals have considerable individual and geographic variation in their underwater vocalizations. Territory holders use the acoustic displays of intruders to locate and challenge invaders and will respond aggressively to a male call. Males assess each other by their vocalizations before deciding whether to respond. These vocalizations are energetically expensive to produce and are honest signals of male quality and dominance. Male body condition will decline as the mating season progresses. Aquatic hierarchies in harbour seals develop before the breeding season and dominance is determined by direct male contests. These contests involve repeated confrontations between two males using surface splashing, fighting, paired somersaulting, and chasing techniques. The hierarchies may aid in holding territories or to mate with females during the breeding season. The dominance relationships are determined by size and sex, with adult males dominant to sub-adult males, and sub-adult females submissive to all other social classes. Aquatic courtship is long in duration and involves rolling, bubble blowing, and splashing to attract females. Female choice appears to play a strong role in this mating system but it has yet to be formally studied. The mating system of spotted seals is quite different from harbour seals as spotted seals are serially monogamous. During the breeding season, a male will join a female approximately ten days before the female gives birth to a pup from the previous years mating. The pairs are considered to be territorial as they keep widely spaced from other spotted seals. The social group consists of an isolated adult pair and the females pup. The female spotted seal receives direct benefits from the male as he provides protection for her and the pup until it is weaned. Immediately after weaning mating occurs. References Phocins Mammal genera Taxa named by Carl Linnaeus