Some possibly do (http://rsbl.royalsocietypublishing.org/content/9/3/20130003 http://rsbl.royalsocietypublishing.org/content/9/3/20130003), but many of the anim

Some possibly do (http://rsbl.royalsocietypublishing.org/content/9/3/20130003 http://rsbl.royalsocietypublishing.org/content/9/3/20130003), but many of the animals that are said to be monogamous are only ever proven to be 'genetically monogamous'. It's hard to prove whether one male's sperm simply outcompetes other sperm.