Why do female mongooses give birth at the same time?

(CNN) – The vast majority of mongoose-to-be moms within a group give birth on the same night. The synchronous arrival of the tiny cubs makes it impossible to tell which mongoose the offspring belongs to.

At first glance, it doesn’t seem like the best approach to parenting, but researchers in the UK say this is a good thing and may even shed light on how the concept of equity evolved.

The fact that virtually all mammals give birth at the same time creates what researchers call a “veil of ignorance,” and this means that parents provide the same care for all mongoose cubs, giving one litter community of up to 20 puppies a better chance of survival.

“In most of the natural world, parents favor their own children,” said Harry Marshall, senior professor of zoology at the University of Roehampton, in a press release.

“However, in ringed mongooses, the evolution of remarkable synchrony at birth has led to the unusual situation that mothers do not know which cubs are theirs and therefore cannot choose to provide additional care for them.”

The researchers studied the behavior of seven groups of banded mongooses, small feline creatures with dark bands on their backs found in parts of Africa, in Uganda. Half of the pregnant mothers in each group were given 50 grams of boiled egg each day, while the other half were given no additional food.

The mongooses that were given the extra food gave birth to larger pups than those that were not, but those differences in body weight did not persist as the mongoose mothers gave special care to the smaller pups.

«This ignorance about the relationship with puppies is key. Our study tests and finds support for the theory that, where such ignorance exists, individuals should choose to invest in the weakest offspring and ‘raise the bar’ for them. They do this because, as far as they know, this lower quality offspring could be theirs, “explained Marshall and study co-author Michael Cant, professor of evolutionary biology at the University of Exeter, in an email to CNN.

“Our study shows that fairness can evolve in animal societies and is not a concept restricted to humans.”

Puppy mongooses next to an adult. Once they emerge from the den, they form caring relationships with another adult, called an escort.

Community nursery

The researchers said that the mongoose mothers nurse all the cubs in their underground dens for a month, without any discrimination, and the cubs feed on many different mothers. Once the cubs emerge from the burrow, they form a caring relationship with the adults, called companions, who can be any adult male or female.

Adults feed and protect the puppy in their care until it can find food for itself at around 90 days of age.

“Companions individually recognize and respond preferentially to calls from ‘their’ particular puppy and actively search for their puppy if it becomes separated or lost,” says the study, published Wednesday in the journal. Nature Communications.

“Puppies, for their part, aggressively defend access to their companion and continually ask for food.”

The study said that synchronous delivery was the key to successful teamwork because on the rare occasions that mongoose moms don’t give birth at the same time, females kill other female offspring instead of caring for them.

It is not known exactly how mongooses are orchestrated by reproducing at the same time, a process that can sometimes involve up to 12 female mongooses. One hypothesis, Marshall and Cant said, is that dominant females produce a pheromone that acts as a signal. However, as the birth occurs in an underground lair, it has not been possible to observe the synchronized arrivals.

“When they don’t, the young almost always die soon after,” they added.