Testosterone response to courtship predicts future paternal behavior in the California mouse, Peromyscus californicus

In the monogamous and biparental California mouse (Peromyscus californicus), paternal care is critical for maximal offspring survival. Animals form pair bonds and do not engage in extrapair matings, and thus female evaluation of paternal quality during courtship is likely to be advantageous. We hypothesized that male endocrine or behavioral response to courtship interactions would be predictive of future paternal behavior. To test this hypothesis, we formed 20 pairs of California mice, and evaluated their behavior during the first hour of courtship interactions and again following the birth of young. We also collected blood from males at baseline, 1 hr after pairing, 3 weeks paired, and when young were 4 days old to measure testosterone (T). We found that male T-response to courtship interactions predicted future paternal behavior, specifically the amount of time he huddled over young when challenged by the temporary removal of his mate. Males that mounted T increases at courtship also approached pups more quickly during this challenge than males who had a significant decrease in T at courtship. Proximity of the male and female during courtship predicted paternal huddling during a 1-hr observation, and a multiple regression analysis revealed that courtship behavior was also predictive of birth latency. We speculate that male T-response to a female in P. californicus is an honest indicator of paternal quality, and if detectable by females could provide a basis for evaluation during mate choice.