Mouse mothers have a hard time: they generally have to look after their offspring alone - their partner elegantly pulls out of the affair. Only under very cramped conditions, such as those prevailing in a laboratory cage, does the Lord take on some of the parental duties; for example, he warms the little ones and offers them protection. But what exactly is it that triggers the paternal instincts in this forced close coexistence? The question has now been asked by the team of Hong-Xiang Liu of Kanazawa University and, in search of an answer, investigated different mouse families.
First, the researchers separated the fathers and mothers from their little ones for a few minutes. In some cases, parents stayed together during this phase, while in others they were housed in separate cages. Then they were put back in the family cage. It quickly turned out that even a few minutes of separation was enough for the fathers to forget all care for their own children - provided that the males were at this time alone and in a clean cage.
Instructions by ultrasound
On the other hand, if they stayed together with their mothers during the separation, they looked after their offspring in exemplary fashion when they returned: they carried him back to the nest, dug him into the cuddly wood shavings and licked him off carefully. Physical contact with the mother, however, was obviously not the decisive trigger: even if the parents had been separated by a Plexiglas disc and could only hear, smell and see, then the fathers showed the caring behavior.
So what is it - hearing, seeing or smelling? An essential factor is apparently the hearing, showed further tests. Because when the mouse mothers are separated from their children, they give off special ultrasound shouts. The fathers react to the observed behavior, the scientists report - even when the calls come from the loudspeaker and there is no female in the vicinity.
Double protection by means of fragrance signals
But that does not seem like the whole story. The nose also seems to play an important role. When the researchers stuffed wax drops into the ears of the mouse men, they were still encouraged to caring - if they could smell the mother. In summary, it could be said that the females in an emergency situation - when they are separated from their offspring - tell the males by scent mark as well as by acoustic signal, what they have to do, my Liu and his colleagues.
These results, according to the researchers, shed new light on the understanding of pair bonds and parental behavior - even if they originate from an unnatural environment for the mice and have so far only been observed in a single laboratory mouse strain. Next, they will now investigate which molecular mechanisms are involved in the process and whether the usual suspects among the socially active hormones - oxytocin, vasopressin and co - play a role here.
Original work of the researchers
- Hong-Xiang Liu (Kanazawa University, Japan) et al .: Nature Communications, doi: 10.1038 / ncomms2336