Photo: Reuters .

This charade sex to establish hierarchy and reduce aggression between males. This activity also in primates, but this is the first time scientists discovered that in animals without backbones.

Donald Edwards scientists at the University of Georgia in Atlanta, US, and colleagues explored Louisiana crayfish in the laboratory. They've seen the type pseudocopulate among males in the wild and in captivity, but its cause is still unknown.

Typically, a male crayfish begins sex opens by approaching the children from behind and provocative "her" with his antennae. Next, he climbs atop her body and flips her over. If her subjection by straightening the legs, males will perform clutched and mating behavior of 30 to 90 minutes.

In 20 pairs of male crayfish tested, sex drama happened in 16 pairs. In 12 pairs of them, as weaker males succumb, pretend sex acts almost like a normal mating takes place from 7 seconds to 9 minutes. In the remaining four cases, males were forced to subdue opposition to this rite.

In the demonstration took place pair mating, the initial action violence between rivals, such as fighting or breaking tails - were significantly lower in the first 1 hour interaction. All the animals survived the first 24 hours.

However, in the double no pseudocopulate procedures, the initial act of violence does not decrease during the first hour. Half weaker males were killed, disarm or be eaten within 24 hours of the first part. 

This suggests that sex plays helped shape the hierarchy between males and reduce the struggle between the rivals.

"In general, aggression or its threat is to establish and maintain a dominant position in the animal community. However, the violence that is dangerous for both dominant and subordinate, because However, many animals find ways to avoid such conflicts, "Edwards said.

In the future, the researchers will continue to investigate whether crayfish females mating with each other or not pretend.