Mouse ‘Doula’ Aids Pregnant Friend in Childbirth

Mice have been observed aiding pregnant females during difficult births, particularly among seasoned mothers. This represents a significant discovery as it marks the first documented instance of such behavior in non-primate animals, broadening our understanding of caregiving behaviors across species.

While humans are recognized as the only animals that consistently assist each other during childbirth due to the challenging nature of the process—characterized by larger-than-average infant head sizes navigating a narrow birth canal—other primates, like black-nosed monkeys and bonobos, have shown instances of mutual aid during births, albeit rarely.

Research conducted by Robert Froemke and colleagues at NYU Langone Health in New York City stumbled upon this behavior while studying the brain activity of mouse subjects during birthing events for a different purpose. They noticed that fellow mice in the cage seemed to assist the birthing mice during their delivery processes.

To delve deeper, scientists genetically modified pregnant mice to lack receptors for oxytocin, a hormone that triggers uterine contractions essential for childbirth. Without these contractions, the mother mouse might struggle to move and face fatal consequences. Consequently, survival for both the mother and her pups becomes more precarious.

In a structured experiment, 10 modified mice were caged individually and each paired with a previously birthing female. A separate group of seven pregnant mice without oxytocin receptors were isolated in their cages.

During delivery, when the modified pregnant mouse could not move, the experienced female stepped in. “She acts like a mini midwife, using her mouth and paws to carefully extract the pups,” shared Dr. Froemke at the Society for Neuroscience conference in San Diego, California. The assisting mouse even broke open the sac surrounding the young, ensuring they could breathe.

A remarkable nine out of ten pregnant mice paired with these midwives successfully birthed, with approximately 90 percent of their pups surviving. By contrast, only one from the isolated group succeeded in giving birth, with all pups not surviving. “Mammals are social creatures, and the primary reason is due to mutual assistance during such vulnerable moments,” Froemke noted. “Even rats experience challenges during childbirth and rearing; their social structures provide support, reflecting traits akin to humans.”

To investigate if the presence of experienced mice was crucial, researchers placed 14 pregnant mice, lacking oxytocin receptors, in a different environment. Seven were coupled with male mice, while four were with females untouched by childbirth and three with females lacking oxytocin receptors. In addition to their role in uterine contractions, these receptors are known to be critical for social interactions.

Results revealed that nearly 60 percent of pregnant mice paired with male companions and half of those with non-mother females endured the birthing process. Notably, these non-mother mice did not assist in pulling the pups out; instead, the male mouse mounted the female, exerting pressure to facilitate the birth, while the non-mother female groomed and applied belly pressure similarly. Differences in approaches among groups remain unclear. Of the group with non-oxytocin receptor females, merely one mouse survived.

The pups did not survive due to the unbroken fluid-filled sacs, indicating the necessity for maternal experience for successful outcomes. “I essentially play the midwife role,” Froemke remarked.

The findings bolster the notion that caregiving behaviors may be more prevalent in the animal kingdom than previously acknowledged. For instance, research has shown that rats are capable of administering first aid to their unconscious peers. These new findings suggest that the birthing and nurturing of offspring are pivotal elements shaping animal social dynamics and relationships, according to Froemke.

“Parental care stands as one of the most significant social interactions,” says Bianca Jones Marlin from Columbia University, underscoring the necessity of support during these critical moments.

Froemke speculates that similar midwife-like behaviors might occur among wild rodents and other animals. “Childbirth represents one of the most vulnerable periods in an animal’s life,” he observes. “Due to their need to evade predators, many animals exhibit concealment behaviors, explaining why field researchers see such assistance less frequently in species outside of humans.”