Species: Rhinopithecus bieti
Habitat: Evergreen forests in an isolated mountainous area of south-west China
Humans aren’t built for giving birth. Babies’ heads are big to accommodate their big brains, but the mother’s hips are small because they walk upright. As a result, birth takes hours and is extremely painful – and midwives almost always help out.
Other animals may find birth difficult, particularly if the babies have been gestating for a long time and have grown large. Nevertheless, most mammals have it easier than humans. Monkeys give birth in less than ten minutes.
So it is a surprise that female black snub-nosed monkeys may be assisted by “midwives” when they give birth. This behaviour has only been seen once in this species, but it suggests that it’s not just human mothers that need help giving birth.
Black snub-nosed monkeys live in societies called bands, which can be over 400 strong. Each is divided into smaller groups of around 10 monkeys. Most groups contain one male and several females plus offspring, but there are also all-male groups.
Wen Xiao of Dali University in Yunnan, China, and colleagues have been observing black snub-nosed monkeys in the province for years, but had never seen one give birth: the monkeys normally deliver at night. Then on 18 March last year, they got lucky.
A female monkey gave birth to her first infant within fifteen minutes late one morning. While sitting in a rhododendron tree, she began twisting her body and calling faintly. After 10 minutes she started screaming, and then another female climbed up the tree. She was an experienced mother, and sat beside the labouring female while the crown of the infant’s head appeared. Once the head was fully exposed, the “midwife” pulled the baby out with both hands and ripped open the birth membranes.
Within a minute, the mother had reclaimed the infant from the midwife, severed the umbilical cord, and begun eating the placenta. A few minutes later, the midwife went back down to the forest floor to forage.
“This is a fairly rare observation,” says Sarah Turner of McGill University in Montreal, Canada, who was not involved in the Yunnan study. She says female monkeys often pull their babies out themselves, and the midwife may have adapted this behaviour. “It’s hard to know what’s going on in her head,” says Turner, but it seems she was genuinely helping.
That could be because female black snub-nosed monkeys tend to stay in the group they were born in. As a result, the females in a group are likely to be closely related and to have strong social bonds. Animals often help their relatives because doing so preserves their own genes, a phenomenon called kin selection.
The juvenile females in the group watched the birth closely, and may have picked up a few tips. Turner says many primates remain with their groups while giving birth, giving juveniles a chance to learn.
In a human childbirth, having help on hand can be vitally important should things go wrong, Wen notes. “The assistance means the infant has a better chance of surviving,” he says. There could be a similar benefit for monkeys aided by a midwife.
But primates, with the exception of humans, rarely help each other give birth. In one case, a male cottontop tamarin was seen pulling at his infant’s shoulders until they emerged. Another report claims that a female capped langur was groomed by other females during birth, perhaps in an attempt to ease her distress.
While primates generally give birth unassisted, other creatures get more help. In possibly the cutest observation in all of natural history, male Djungarian hamsters regularly assist with deliveries, pulling infants out with their front paws and incisors.