Wednesday, January 31, 2007

Why Is It Beneficial to Have a Stable Sex Partner?

Living in couple means investing your genes in just one variant, and, like a gambling, he/she may be the best, right, not right or the worst.

But there must be an advantage in forming a monogamous pair, besides securing a sex partner, because animals have sex just during the mating season. Otherwise, they wouldn’t exist.

This is a scene not very rare in the African reserves: a herd of lions is devouring a zebra corpse, when suddenly, in the middle of the feast, a female jackal appeared, right under the nose of one lion.

The pissed off lion charged roaring towards her, but the little thief avoided it. At the same moment, another jackal appeared, stole a piece of meat and ran with it. A few hundred meters away, the male jackal shared its prey with its partner, which helped it in this diversion. On the way to their den, an eagle attacked the male jackal, thrusting its claws into its back. Then the female rushed, jumped and hit the eagle with such a power, that the eagle released its claws from the jackal’s fur and rolled over the ground.

Few days later, the male was turning back from a hunt while he found a hyena, three times his size, trying to dig up the den and eat the female.

Only the back of the hyena was visible and the male inflicted to powerful bite to the hyena’s bottom.

The hyena jumped like it would have been

burnt and turned around preparing to attack.

The next moment, the female leaped out of the den and together with its partner managed to chase away the hyena.

It’s clear: a pair achieves more food and survives better than the bachelors. That’s why the jackals spend every morning about 30 minutes grooming each other (photo above), an activity that strengthens the bond between the two.

The “married” jackals were found to live on average 3-4 years more than the solitary ones.

Of course, this is available for other mammalian species forming couples, too.

Amongst the monkeys of the Old World, only the gibbons form stable monogamous pairs (photo center).

After the age of 18, for the “married” gibbons the retirement period starts.

They can no longer produce offspring, losing the parents quality, but they are accepted by the “family” of one of their offspring, as grandparents.

This way they profit from the community protection and when it’s about feeding, they can get some scraps.

The solitary gibbons do not pass the retirement age, as they won’t be able to defend and feed themselves.

Couple life is rather rare amongst mammals, being found amongst some carnivores, monkeys and antelopes (dik-dik). In birds is something much more common.

The families can form colonies, which can be huge in the case of the marine birds (like gulls, albatrosses, petrels, penguins, auks and others), but not necessarily (crows, weavers).

In the case of the gulls nesting on steep rocks in the Northern Atlantic, the advantages of a marriage are huge.

There are many gulls looking for the best spot, but only the stable couples manage to keep their nest: while one is gone searching for food, the other remains guarding.

Lone gulls often lose their sleeping place, and the worst places are those where there is the risk of being hit to the rocks during the storms and die.

Some gulls simply can’t find the right partner.

In this case, the marriage is a continuous quarrel and the partners die at an early age.

Growing offspring would be less costly than family fight.

Researchers found that “married” gulls reach the age of 26, while the bachelors and the quarrelsome barely overpass eight.

The macaws (photo below) not only marry, but they also plan raising offspring.

A pair that lives harmoniously can reach 45 years.

Macaw females lay just 2 eggs, once every five-seven years.

This way, a density of three macaw pairs at five square kilometers is maintained naturally.

They are equally peaceful with their neighbors as they are inside their family.

And their croaking, which can last for hours, is not a fight but simply their way of making love declarations, declarations that last till they die.
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