PRINCETON, N.J. – Male caregiving is rare. Of the nearly 6,000 mammalian species, fewer than 5% of fathers stick around to raise their own young. Most are even instinctively hostile.
Even among the mammals that pitch in with caregiving duties, including humans and a handful of rodents, there's still a range of caregiving quality, from contenders for "Dad-of-the-Year", to at worst, abusive.
"Why is it that some males are caring while others are neglectful?" said Forrest Rogers, Ph.D. , a postdoctoral researcher at Princeton University in the labs of assistant professor of neuroscience Catherine Peña , Ph.D., and associate professor of molecular biology Ricardo Mallarino , Ph.D.
Now, a new study led by Rogers reveals a molecular "switch" in the brain that may account for the difference between a doting dad and a neglectful or abusive one.
The findings were published February 18 in the journal Nature.
The male brain on babies
To understand this range of parenting behavior, Rogers turned to a rodent called the African striped mouse.
Both in the wild and in the lab, striped mouse males vary in their nurturing tendencies and parenting styles. The best caregivers take an active role in looking after the young, licking and grooming pups to keep them clean, or nestling them under their bellies to keep them warm and safe from the elements. The worst ignore helpless pups or even attack them.
To determine what parts of the brain reflect these parenting differences, the researchers put striped mouse males in different environments with and without pups and mapped their neural activity.
They found that a specific brain region acted as a "parenting hub." Neurons in the medial preoptic area (MPOA) became significantly more active when they came across a pup.
Not every male, however, experienced the boost to the same degree. When the researchers compared males that were caring towards pups with ones that were more standoffish or hostile, caring males showed greater activity in this region than neglectful ones.
Scientists have long known that new mothers of other rodent species — such as voles, hamsters, and rats — also undergo changes in the MPOA, suggesting the brain region is similarly rewired in moms as well as paternal striped mice.
"But in the case of these males, it's not pregnancy or even parenthood that transforms their brains," Rogers said. "Bachelors can be just as capable of caring as experienced dads."
Rogers found instead that males who spent more time caring for pups had lower levels of a specific gene called Agouti in their brains.
"Agouti is better known for its roles in skin pigmentation and metabolism, so discovering this previously unknown role in the brain for parenting behavior was exciting," Rogers said.
A caregiving switch
The team then uncovered that certain environmental conditions influence Agouti levels in the MPOA, which in turn affect males' behavior toward pups.
If males lived alone, they had low levels of Agouti and were more likely to become nurturing adults.
Males that lived in groups, on the other hand, had naturally higher levels of Agouti and devoted half as much time to childcare compared with males who lived a solitary life. High levels of Agouti even appeared to suppress neural activity in the MPOA.
To better understand how the Agouti gene affects parenting, the researchers used gene therapy to artificially boost Agouti levels in the brain, mimicking the natural biology of a neglectful dad.
When males re-encountered pups after treatment, they showed less interest in pups than they had before, with some even becoming aggressive. Agouti, in a way, acts like a molecular "off switch" for caregiving in the brain, turning attentive males into neglectful or even abusive ones.
As a natural "treatment," the researchers later moved some males from a communal living arrangement to a solitary one and found that Agouti levels dropped and males took more interest in pups.
Figuring out fatherhood
Taken together, the findings support a growing body of research showing how experience can alter gene expression in developing brains that affect parenting behavior later in life.
"Our findings point to Agouti as a potential evolutionary mechanism that allows animals to integrate environmental information, such as social competition or population density, and adjust the balance between self-preservation and investment in offspring," Mallarino said.
The researchers are still working to identify the specific environmental cues, including crowding or competition for food and mates, that cause Agouti levels and interest in pups to rise and fall.
While the MPOA and the Agouti gene are both found in humans and striped mice, the team cautions that it remains unknown whether these same mechanisms regulate paternal behavior in people.
"Parenting is a complex trait. We're not suggesting that you can take a pill to become a better parent, or that struggles with parenting reflect some molecular deficiency," Peña said.
By studying the biological changes that support fathering in species that are naturally paternal, the researchers hope their findings shed light on factors that place some father figures at greater risk for child abuse and neglect.
This research was supported by Princeton University, the New York Stem Cell Foundation, the Vallee Foundation, and grants from the U.S. National Institutes of Health (F32 HD110180, R35GM133758).
CITATION: Agouti integrates environmental cues to regulate paternal behaviour. Forrest Dylan Rogers, Sehee Kim, Sarah A. Mereby, Anna M. Kasper, Anastasios B. Callanan, Ricardo Mallarino, and Catherine Jensen Peña. Nature, February 18, 2026. DOI: 10.1038/s41586-026-10123-4
