Male caregiving behavior is a critical aspect of human social behavior and human evolution, though it has traditionally received less research attention from neuroscientists precisely because it is uncommon in most other species (Kenkel et al., 2017). Male caregiving takes two forms, paternal care and alloparenting -i.e. the provisioning of care by individuals other than the young’s biological parents. Understanding both modes of caregiving by males is critical to understanding its dysfunction and thereby informing interventions. Alloparental care is a universal behavior among human societies (Sear and Mace 2008). Meanwhile, in our closest living relative, the chimpanzee, alloparenting is displayed only very rarely (Kishimoto, Ando et al. 2014). In order to accomplish the feat of having large offspring who develop quickly, humans are believed to have employed a communal/cooperative breeding strategy with a high level of alloparenting (Kennedy 2005, DeSilva 2011).

Alloparenting remains critically important in contemporary culture. By the age of 3, over 90% of American children have experienced regular alloparental care (Network 2001). Understanding dysnfunctional alloparental care is crucial because children are somewhere between six (Schnitzer and Ewigman 2008), eight (Stiffman, Schnitzer et al. 2002), fifty (Schnitzer and Ewigman 2005), or even a hundred (Daly and Wilson 1988) times more likely to suffer fatal abuse when living with an unrelated adult, i.e. while under alloparental care.

My work has largely focused on alloparenting by male prairie voles, though I have also studied paternal care by vole fathers as well as female alloparenting. When presented with a pup, prairie voles experience a surge of oxytocin and diminished levels of corticosterone (Kenkel et al., 2012). Centrally, oxytocin neurons are activated, while corticotrophin-releasing hormone neurons are inhibited. All this suggested the pup might produce a calming, anxiolytic effect on the alloparent, which was supported by behavioral measures of anxiety.

However, when I recorded alloparental voles’ heart rates using implantable radiotelemetry, I found that alloparents’ heart rates were sustained at near maximal levels (Kenkel et al., 2013). Outwardly, the alloparents appeared calm, but certain aspects of their physiology were evidently very worked up. I next set about trying to test alternative hypotheses to explain this effect and found that it could not be explained by: novelty, locomotion, experience, duration, or sex. The eventual explanation for the high heart rates came when I tested caregiving voles with pups in warmed environments which abolished the caregivers’ cardioacceleratory response, thereby showing that the need to provide pups with warmth had caused the high heart rate (Kenkel et al., 2015). One lesson of this work was the importance of assessing a phenomenon from as many angles as possible -hormonal, behavioral, neural, and autonomic approaches may all be needed to arrive at a fully integrated understanding