I've just been reading an article about an experiment with birds in which males where provided opportunity to associate a specific set of stimuli with the chance to mate, and were also placed the same number of times in another place where they did not form similar associations.
When two birds who has been in each 'box' where allowed to mate the female in quick succession, those that had been exposed to the stimuli predictive of the chance to mate fathered much more of the litter.
http://www.medicalnewstoday.com/articles/84623.php
I have heard of ppl setting their dogs up to form similar associations, with being put on a particular lead or harness or taken to a particular area or similar being used to get their dogs revved up before they even got near the bitch. I wondered about it, it seemed to risk problem behaviour to me, that dog might get too excited and difficult to manage, it hadn't occurred to me that it might enhance fertility.
Libby