We call them colonies, but they are in fact just huge harems. In the case of the northern fur seals, the first to invade the beaches in March are the males. Once they reach the sand, they become aggressive with each other, fighting for the best spots. They do not even go fishing into the sea, to keep the best locations.

For 2-3 months, their life means fight and hunger, in a general uproar, in blizzard and fog conditions. This is what they like, as on sunny days, the weather gets so harsh for them that they temporarily stop the fights. Around the middle of June, the agitation increases, as thousands of females come from their 6,000 km (3,750 mi) journey, from the shores of California to Alaska (those from Siberia come from Japan and Korea).

Now, males stop the fights, as hierarchies have been established, and they try to lure as many females in their harems. Anyway, the best spots attract most females. Once a female has been "fooled" into the territory of a male, he cuts off her retreat passage, grabs her with the jaws from the nape and throws her over the crowd of already conquered females. The best tactics can produce harems of up to 100 females.

The males must be alert not only that the females cannot escape, but also to their neighbors, who do not escape the opportunity to steal from his females. If the "owner" takes notice of the theft, the poor female can become the object of a rope game (in which she is the rope), in which one males pulls her from the tail and the other from the nape.

Soon after the harems' formation finishes, the females start to give birth and soon after that enter in the fertility period. Sometimes, the sultan cannot accomplish his duty due to the continuous fightings in which he is not always the winner.

The loser males can suffer severe wounds, which makes them more vulnerable to the attacks of a great white shark or an orca (killer whale). Sometimes, they gather in "associations of the frustrated", far away from the main colony.

Mothers too struggle for the best places, far away from the males' turmoil, because in their skirmishes, males do not attentive to the offspring, which can be accidentally smashed. The best places for the mother are near rocks close to the beach, under which the offspring can easily hide if necessary.

After mating, the male relaxes the loop, and the females can go fishing, leaving the offspring alone. If she gets killed by a predator in the sea, the orphan is doomed, as neighboring females will not feed it, no matter how much milk they have; oppositely, females are aggressive to foreign young, beating and pushing them away. The mothers and the offspring recognize each other by their call.

This scenario is valid also for the relatives of the fur seals, the sea lions. But amongst the true seals, only the elephant seals form such huge harems. What about the other species?

They too form harems of 30-50 females, with beach owners, only that their colonies are looser.

Why do seals form the harem system? Biologists say that this way the best males, with the best genes, will deliver the healthier offspring. But when researchers analyzed paternity in a seal colony, they were surprised to find that one in three seal pups were not fathered by the beach master! Moreover, even if the beach master remained for years the same males, a "hidden lover" could have been the father of a female's offspring for years! Thus, the females were found to even be faithful to their lovers!

The females cheated the sultan with low rank males, prowling around, which get into the beach when the master is not aware, mate with an unfaithful female and quickly disappear.

They make their appearance especially during the night or in foggy time, when the male gets it harder to watch upon his harem. Sometimes, a daring females enters the sea mimicking food search, while she is just on the look for an affair.

In fact, the worst places for a female are those close to the harem's owner. The best places are the edge ones for exactly these two reasons: to avoid the killing of her offspring during the males' fights and to have the opportunity to choose "lovers" at her wish. It appears that the harem life of the seals is determined by the scarcity of the proper breeding places, like just a few small beaches.

Seals living more to the poles form more monogamous relationships. The "ladies" are located so far one from another, that the "husband" has no chance of paying a little visit to a neighboring one.

One thing is certain: the females are not so dependent on the sultan. And the lover-system could ensure a more varied gene influx in the population's genetics.