Bats

For men bats, the intelligence comes at a heavy price. A new study has revealed that the bat species with large brains smallest testicles.
The correlation is probably a compromise between development, have a large brain and the production of shipments of semen, said Scott Pitnick, biologist at the University of Syracuse in New York, he at the forefront of research.
"The man multiplier's the greatest number of sperm May this game to win, and hence many bats have large testes scandalous," said Pitnick. Because they live with a knife energy demand shows bats May not be able to drive their development, the testes and big heads. "
Female bats in many species mate with more than a simple man, and the sperm can enter the body of the woman during the long period leading to a fierce competition between sperm to fertilize the egg. Pitnick suspected that the men, the testicles relatively large and small brains leave more that the large-brained children and less fertile competitors.
In the study, Pitnick and his colleagues studied 334 species of bat, and noted that the species with the promiscuity of women, men have larger testicles, but relatively small brains. In species where the women are loyal to their companions, the link has been made. The study also showed that the men of loyalty seems to have no effect on the testicles or size of the brain.
In some species of bat, the testicles of males can be up to 8.5% of body mass. Of all mammals, the bats the largest selection of testicular mass: between 0.12 percent and 8.5 percent of body mass.
By comparison, the mass of the testicles in primates (including humans) varies from 0.02 to 0.75 percent