The mating itself can alter the physiology of the female mammal, even if pregnancy does not occur. To such conclusion the group of Australian and new Zealand scientists, who have settled to mice of different males: healthy, unable to conceive and unable to mate. It turned out that such a neighborhood affects the lives of females, even after cessation of contact with the males: those who had the opportunity to mate, not having, subsequently more prolific, but die early. The authors suspect that it is the hormone prolactin, which appears in the body of the female after mating. A study published in the journal Proceedings of the National Academy of Sciences.
Procreation — the process is energy-consuming. It robs the parents (primarily the mother) the resources which it could spend on their own body. It is logical to assume that reproduction should reduce the number of resources in the mother’s body and therefore years of life.
At the same time, the production of offspring can be divided into two parts — mating and pregnancy. Which one has stronger effect on the further life of the mother is unknown. Although the gestation of the offspring, it would seem, takes more energy, it is known that even contact with a sexual partner in some of the animals can affect the metabolism. For example, flies have a meeting with a female can shorten the life of the male.
To study the effect of mating apart from pregnancy, Michael Garrett (Michael Garratt) from the University of Otago in New Zealand, together with colleagues gave mice females to males after vasectomy. Such males are able to mate, but can’t fertilize the female. For comparison, the researchers gave a control group of mice to females, fertile males, or castrated males, which have impaired production of androgens, so they are not capable of not only fertilization, but also on grooming. Females spent in the company of partners 9 months of his life, from the 2nd to the 10th, and then they are resettled or in a separate cell (to measure the survival rate) or in cages with fertile males (to evaluate fertility).
Changes in the physiology of mice began in the first months of life with partners: females began to gain weight. And it affected those who lived with healthy males, and those who were put to vasectomypenis males. Neutered males and females such influence on its neighbors has not had what the researchers concluded that the effect caused by the act of mating itself. After that, females have settled out from the neighbors, and the changes in weight is preserved only in those who have settled to the new, healthy males, it is allowed to multiply.