The California mouse and the deer mouse are very similar, except California mice find one partner and mate with them for life, while deer mice take on as many mates as possible. That lifestyle difference has a major biological impact.
While debates rage among humans over the value of promiscuity, the argument is settled among honey bees. New evidence from several scientific studies suggests that queen bees who mate with multiple males are able to build healthier hives that are more productive, well-fed, and disease-resistant than hives where the…
From a strictly evolutionary perspective, there's no reason why female beetles should be promiscuous. Unlike males, taking on multiple partners won't allow females to spread their genes more widely, and too much sex can actual shorten the female beetle lifespan.
Men have always had evolution to blame for their wily Cassanova ways—that whole spreading their seed far and wide thing. Finally, evolution is coming through for women, too!
Like humans, zebra finches form monogamous partnerships in order to rear children. And, very much like us, these birds are also known to indulge in "extramarital" sex, even when these affairs serve no obvious evolutionary purpose.