ScienceDaily (Aug. 8, 2011) Scientists at the University of Liverpool have found that male fruitflies experience a type of 'paranoia' in the presence of another male, which doubles the length of time they mate with a female, despite the female of the species only ever mating with one male.
Females in many species of animal have multiple mates and males have evolved particular reproductive characteristics to ensure their sperm are successful when in competition with the sperm of other males. Adaptations include physical traits that result in increased sperm count, as well as behavioural alterations such as mating with females for up to 21% longer than they normally would.
& 
Compatiable 