Few species of mammals — only about five percent — are bi-parental, with both males and females showing high levels of care to their offspring. The California mouse (Peromyscus californicus) is among these rare species and has attracted the attention of behavioral neuroendocrinologist Elizabeth Becker, Ph.D., who’s kind of a rare breed herself. Behavioral neuroendocrinology is a rather specialized field, with few active researchers. Dating back to her doctoral studies, Becker’s research looks at neural and hormonal mechanisms underlying the development of social behavior in animals and humans.

“My training in neurobiology and psychology has led me to explore the complex questions of the nature versus nurture debate: How much of our behavior is determined by genetics, and how much by our upbringing?” asks Becker. “I’m particularly interested in the ways in which our social interactions can change our biology.”

Becker’s research looks at the California mouse to explain parental effects on development of the offspring brain. While many studies have shown that mother-offspring interactions from infancy help to shape brain and behavior, with paternal care being rare in mammals, the role of fathers has been understudied. The goal of Becker’s research is to clarify the importance of dads in early-life interactions.

“Simply put, since we know that mothers can influence behavior, my studies examine how, through changes in the brain and hormones, fathers and their style of parenting affect their offsprings’ — more specifically, their male offsprings’ — behavior into adulthood,” explains Becker.

Becker and her team of student researchers have performed a number of studies examining the influence of paternal retrievals (a behavior that involves fathers grasping their pups by the scruff of the neck and carrying them back to the nest) on offspring development. This set of studies focuses on fathers, because in the wild their presence is related to survivorship, and retrievals, because they hypothesize that retrievals protect the offspring from dangers outside of the nest.

Lab studies have allowed Becker and her team to manipulate the number of retrievals an offspring experiences and examine changes in brain, hormones and behavior. They’ve found that male pups who are retrieved more often by their fathers, have an increase in the hormone testosterone, leading these pups to be more aggressive and better parents as adults. The result is important for the California mice because males may need to be aggressive to protect their territory, offspring and mates in the wild. Further, in a recent study, Becker has shown that males who receive high levels of care from their fathers also show high levels of care toward their own offspring.

Although Becker’s research focuses primarily on father-son relationships, some of her newest research on father-daughter interactions has resulted in some interesting discoveries. Becker has identified a similar spike in testosterone production for female pups who are retrieved often by fathers.

“Understanding that parental behavior is linked to the care one receives early in life has important societal implications,” says Becker. “It should give hope to adoptive parents that the love they give their children will significantly influence who they become as adults. Research of this nature will also help us understand the biological mechanisms underlying the cycle of abuse that is repeated when children are victims.”

Currently in the Becker lab, they are examining the mice’s brains to determine whether changes in receptor expression underlie the development of paternal behavior and aggression. They suspect the answer lies in the brain because research between mothers and daughters indicates that this is so.

“We know so much about mothering and the role it plays in shaping the brain, but mammals like the California mouse can teach us how fathers factor in,” says Becker.