Male mammals may invest heavily in reproduction through efforts to enhance reproductive success (e.g., courtship displays, intrasexual combat) or to provide paternal care. However, the costs of paternal care have rarely been studied in mammals, in large part because only 5-10% of mammals exhibit such care.[9][10] Nonetheless, in those species in which males do provide extensive care for their offspring (i.e., biparental species, including humans), indirect evidence suggests that its costs can be substantial. For example, mammalian fathers that care for their young may undergo systematic changes in body mass and in circulating or excreted concentrations of a number of hormones (e.g., androgens, glucocorticoids, leptin) as a function of reproductive status,[11][12][13] and several of these hormones have important effects on body composition, metabolism, and organismal performance.[14][15] Nonetheless, the energetic and performance consequences of male parental investment have rarely been investigated directly in mammals.[16]
In mammals, paternal care is found most commonly in primates, rodents and canids.