Testosterone induces a conditioned place preference to the nest of a monogamous mouse under field conditions

Transient increases in testosterone (T-pulses) occur after social interactions in males of various vertebrate species, but the functions of T-pulses are poorly understood. Under laboratory conditions, the rewarding nature of T-pulses induces conditioned place preferences (CPPs), but what are the effects in a complex field environment? We present the first evidence that T-pulses administered to males at their nest site in the wild increased time spent at the nest regardless of pup presence in the monogamous, biparental, and territorial California mouse (Peromyscus californicus). Female partners of the T-males, in turn, spent less time at the nest. Independent of treatment, mice produced more ultrasonic vocalizations (USVs) when alone, but T-mice produced more USVs than controls. T-males produced USVs with a smaller bandwidth that likely traveled farther. Our combined results provide compelling evidence that T-pulses can significantly shift the behavioral focus and location of individuals in a complex field setting.