It's not the best parallel but it reminds me of the "breeding policies" of kanguroos. They can have actually § offsprings in diffrent states of developement. - a "toddler" which already leaves the breeding badg - a "baby", which is still grown together with a teat in the breeding bag - and an embryo (hibernating in a very early state) in the uterus. Fast replacement if one of the offspings dies. It's not so much about guarding the females but about as fast as possible replacement. That is ... in case this theory will hold.