What could be unusual in that mating increases fertility? After all, mating usually ends in conception, especially in animals; it would be strange if mating fecundity diminished. But in mating, nevertheless, there is actually mating, and there is conception. And so the researchers from University of Otago decided to find out whether mating by itself affects the body.
For this, young female mice were introduced to barren males – animals could mate, but no offspring appeared. Females were then watched throughout their lives. It turned out that mating has long-lasting consequences: mating females grew larger, but at the same time they lived less than females that did not mate. If, after some time, both were provided with ordinary, prolific males, then females with mating experience gave birth to more cubs. That is, mating by itself, in addition to pregnancy, milk production and everything that follows conception, affects the female – she will live on average less, but she has a chance to bring more offspring. True, this effect was only from mating with sterile males: in an article in PNAS it is said that if young females were allowed to mate with ordinary males from the very beginning, from whom they could become pregnant, then later they brought less offspring.
Similar results were obtained earlier in experiments with insects, but such studies have not yet been conducted with mammals. What physiological mechanisms are working here, for now, one can only speculate, although it is obvious that hormones regulating sexual behavior and pregnancy should work here. It would be interesting, by the way, to check whether mating affects the life expectancy and fecundity in males. (As for early fatherhood, we once wrote that it shortens life for men.)
Whether the obtained results apply to people is also not yet known. But, probably, they will be useful in animal husbandry, where, in order to increase the fecundity of any animals, it is possible to carry out, so to speak, installation mating with sterile males.