UC Riverside Undergraduate Research Journal

In many biparental mammalian species, such as California mice (Peromyscus cali- fornicus), new fathers exhibit affiliative behavior toward unfamiliar infants, whereas reproductively naïve males show highly variable behavioral responses to infants. The sources of this variation are unknown. We investigated the effects of acute stress on pup-directed behavior in reproductively naïve male California mice. Each mouse underwent three 10-minute tests with an unfamiliar pup at 48-hour intervals. Males in the stressed group (N=22) were stressed using subcutane- ous oil injections, a common experimental stressor used in rodents, immediate- ly before each of the first two tests. The controls (N=22) were left undisturbed to avoid any experimentally induced stress. Compared to controls, stressed mice spent significantly less time performing paternal behavior in tests 1 and 2, while only marginal differences were seen in test 3. In tests 2 and 3, signifi- cantly fewer stressed mice interacted with the pup than controls. These findings suggest that acute stress experienced by reproductively naïve males might con- tribute to both short-term and long-term differences in pup-directed behavior.