It is usually thought that men share only symbolically, if at all, in the experience of pregnancy, but recent studies have shown that paternal males undergo changes in the same hormones as maternal females. The work promises to biologically verify the experiences of new fathers.
Among mammals, males typically do not provide direct paternal care. In some species, such as rats, males will attack and consume newborn young at sight. But in species whose males do provide paternal care, there is evidence that hormones mediate the onset and the maintenance of paternal behavior.
This is most remarkably shown in Djungarian hamsters (Phodopus campbelli), whose males act as midwives during birth. They pull pups from the females, lick off birth membranes, open the pups' airways and clean up the amniotic fluid and the placenta. The males even clean and rebuild the nest area, and baby-sit when the female goes off to feed.