A family is nor only a social unit, but also a reproduction unit. Since we were children, we know that only fittest survive. From ecological point of view the fittest one is the one who has more offsprings. In order to succeed, one shouldn’t rely on himself, but also find an appropriate partner (according to Darwin’s opinion that breeding pairs do not form accidentally). But traditional beliefs that most fertile females and most aggressive males win the game, simplify the situation. Females choosing the father of their future children, want him to care about little ones.
 

According to the research, recently performed in RAS CB Institute for Animal Systematics and Ecology under the supervision of RAS corresponding member Evsikov V.I., even laboratory mice worry about this problem. And the solution for mice lies in the smell.
 

In the course of the experiment the scientists from Novosibirsk allowed female mice to choose a partner. A female, ready for mating, nosed two male mats. The scientists took the mat, which got more attention, and put it to other male mats. If the female chose this mat again, she mated the mat owner. The couple was settled together and gave birth to three broods. On the next day after little mice were born, their fathers were tested for parental care. For this purpose parent mice were taken out of the cage and little mice were moved to the corner opposite to the nest. Then the father was returned and was considered to be a bad father if he didn’t bring any of his children back to the empty nest within 10 minutes.
 

The scientists continued selection among newborn mice. After five or six selection stages the share of caring fathers in the test group was almost twice as high as in the control group. It’s pleasant to note that next generations keep their fathers’ good qualities. The more “children” a mouse has, the more caring the father is. 46% of fathers cared about their first brood, and 68% cared about their next broods.
 

But how do males combine their care with aggression necessary for success? And how to measure it? Scientists leave males by pairs for 10 minutes and count all contacts between them. Females appear to choose males, whose acts of aggression share about 60% of all contacts with other males – average level of aggression. Males, which appeared to be more aggressive, were bad fathers, and dull and spiritless males are useless.
 

Those females that make a good choice are good mothers themselves. During the period of mother care almost none of the little mice die.
 

So, mice are like human beings. Women, who are serious about the family, marry a good father – attentive and able to care about his family. Should we wonder that scientists spend so much time with mice?