Don't think that only humans live in marriages.

Wild cats, too, live in families with strict rules when it comes to sex.

Only the 2-3 dominant males in a pride father the cubs. And this is the case of leopards and tigers, too.

A male dominates the territory of 2-3 females, which form their harems, and they will mate only with him, even if they rarely meet (it's like spouses sleeping in different rooms...).

The female cheetahs that prowl the Serengeti in Tanzania appear to live up to their name, scientists have shown. The gracious cheetah females break the rule: DNA analysis discovered that they are serial cheaters, and about 50 % of their litters are fathered by more than one male, a risky behavior that could on the other hand boost the genetic diversity of this imperiled species. "If the cubs are genetically more variable it may allow them to adapt and evolve to different circumstances. If there is a big change in the environment some may be able to cope better", said co-author Dada Gottelli of the Zoological Society of London (ZSL).

Cheetahs (Acinonyx jubatus) are classified as vulnerable and the effective breeding population is estimated to be less than 10,000 individuals in Africa, being further threatened by habitat loss and poaching by farmers, while the Asiatic cheetah, persisting just in Iran, could have effectives of no more than 60 individuals.

The new 9 years study was made on a cheetah population in the Serengeti National Park (north-west Tanzania). DNA analyses from the fecal samples of 176 cheetahs showed that from 47 litters of cubs, 43% were fathered by two fathers, sometimes even three.

The phenomenon may occur in the case of other big cats, too, but it is not so rampant. "If anything, this is an underestimate. Cheetah cubs suffer high mortality on the first few weeks so it was difficult to get samples from all of them", said Gotelli.

Female cheetahs release a new egg with each mate, the so-called induced ovulation, common in cats and other mammals, like rabbits. This means that each egg can be fertilized by sperm from a different male.

The cheetah female's high promiscuity can render them more vulnerable to predation, parasites and disease, but this is a powerful factor against inbreeding and may also protect the cubs from neighboring males. "Infanticide has not been observed in the wild cheetahs, like it has been in lions, tigers and leopards. Maybe this is why. It may create confusion in the males. In that case it's better not to kill any cubs in case they were yours." said Gotelli.