Wild mice reveal secrets: scientists explore the origins of humanity's strongest emotions.

The study of Peromyscus mice, agile wild rodents from North America, resembles Aesop's fable of the city and country mouse, reflecting the diverse lifestyles of these creatures and their habitats. Unlike their well-studied lab counterpart, Mus musculus, these mice exhibit a rich natural variability in behavior. This variability has enabled scientists to explore some of the strongest instincts prevalent in humans, as noted by The Scientist.

This behavioral diversity makes wild mice invaluable for investigating the genetic and neural influences on traits such as parenting, mating habits, and responses to threats. The behavior of Peromyscus species, ranging from monogamy and selfless parenting to promiscuous mating and minimal care for offspring, has provided researchers a glimpse into the complex world of social nature.

For over a century, naturalists have marveled at the behavioral variability of these mice across North America. With the advancement of molecular technologies, researchers have begun to delve deeper into their neurobiology to understand these unique forms of behavior. Unlike lab mice, which often lack genetic variability, Peromyscus mice, whether captured from the wild or maintained in laboratories as external strains, allow for rigorous testing in controlled settings.

Many species of this genus can interbreed, facilitating genetic studies that link specific genome regions to various behaviors. This natural variability, as highlighted by Felix Bayer from the Max Planck Institute for Brain Research, enhances the value of these mice as models for behavioral studies.

Parental behavior in Peromyscus species varies significantly, serving as a clear example of behavioral and genetic diversity. In species such as P. polionotus (the Oldfield mouse) and P. californicus (the California mouse), both parents actively participate in raising their young, which is rare among mammals.

A study led by Andres Bendeski, now at Columbia University and published in the journal Nature, showed that such behavior is largely hereditary. Cross-fostering experiments revealed that offspring adopt the behavior of their biological parents regardless of the rearing conditions.

Some studies also indicate genetic factors, such as the expression of vasopressin precursor genes in the hypothalamus, affecting parenting strategies and nest-building quality. Threat response behavior is another area of intrigue. In his research, Bayer compared species such as P. maniculatus (the eastern deer mouse) and P. polionotus, discovering differences in threat reactions influenced by habitat. While P. maniculatus, residing in dense vegetation, quickly flees from danger, P. polionotus, adapted to open fields, initially freezes.

Neuroscientific studies have shown that the dorsal periaqueductal gray (dPAG) area of the brain plays a crucial role in these responses, with activity levels correlating with escape speed. Finally, studies of fatherhood in monogamous species, such as the California mouse, have revealed neural plasticity associated with parenting. Wendy Saltzman from the University of California, Riverside, investigates whether fatherhood alters auditory systems for better detection of pup vocalizations, indicating sensory adaptation in parental roles. R

The Peromyscus genus, with its natural diversity and ability to interbreed, presents a promising model for studying the genetic and neural foundations of behavior, offering insights that are unavailable with traditional lab mice. This research enriches our understanding of evolution and the interplay between genetics, environment, and behavior, opening possibilities for comparative studies of other mammals while shedding light on human behavioral traits.