Scientists have observed mice assisting pregnant females during difficult births, marking the first such behavior documented in non-primates. Experienced mother mice proved most effective in aiding delivery. This discovery challenges assumptions about caregiving in the animal kingdom.
Researchers led by Robert Froemke at NYU Langone Health in New York City stumbled upon the behavior while studying brain activity in mice giving birth. In a separate experiment, they genetically engineered pregnant mice to lack oxytocin receptors, which are crucial for uterine contractions. Without these, pups often get stuck in the birth canal, endangering both mother and offspring.
To investigate, the team housed 10 such pregnant mice with female companions who had previously given birth to at least one litter. During labor, these 'midwives' intervened when pups became stuck. "She will come over and act like a little mouse midwife and very carefully, with her mouth and with her paws, pull the pup out," Froemke described. The assistants also broke open the fluid-filled sacs around newborns to help them breathe.
Nine of the 10 paired mothers survived, with about 90 percent of their litters also surviving. In contrast, only one of seven solitary pregnant mice survived, and all pups in that group died.
Further tests showed that prior motherhood experience was key. Pregnant mice paired with males saw nearly 60 percent survival through males mounting to apply back pressure, but no pup extraction occurred, and none of the pups survived due to intact sacs. Half of those paired with non-mother females survived via grooming and abdominal pressure, yet again, pups did not. Pairings with females lacking oxytocin receptors yielded only one survivor out of three.
"It seems that the experience of being a mother is required to be a successful [mouse] midwife," Froemke noted. He presented these findings at a meeting of the Society for Neuroscience in San Diego, California.
The results suggest caregiving during birth is more widespread among animals than previously thought. "There are a lot of reasons mammals are social, and a primary reason is to help each other out, especially in these really vulnerable periods," Froemke said. Bianca Jones Marlin at Columbia University emphasized that parental care "requires support."
Froemke suspects similar behaviors occur in wild mice and other rodents, hidden from observers due to the vulnerability of birth, when animals seek seclusion from predators.