Over the past 20 years, long-term studies have shown that mammalian fathers, brothers and even unrelated males may contribute substantially to the care of the young. Recently, more field studies of mammals with male care have further expanded interest in male care potential. Male mammals can never be sole care-givers because offspring depend on maternal milk, but assistance provided by males may allow females to produce more energetically costly litters. The need for such male care contributes to the development of obligate social monogamy or communal breeding.
Woodroffe, R. & A.C.J. Vincent. (1994). Mother’s little helpers – patterns of male care in mammals. Trends in Ecology and Evolution 9:294-297. https://doi.org/10.1016/0169-5347(94)90033-7