Environment

Mongooses Wear Themselves Thin Being Devoted Babysitters

Animals do the most amazing things. Read about them here in this series by Janaki Lenin.

The researchers investigated the cooperative behavior of "babysitting" and "escorting" young. Credit: Harry Marshall

The researchers investigated the cooperative behavior of “babysitting” and “escorting” young. Credit: Harry Marshall

Male banded mongooses have distinct personalities. They are either selfish or cooperative throughout their lives.

Professor Michael Cant and his colleagues from University of Exeter, U.K., observed hundreds of banded mongooses in 14 groups in Queen Elizabeth National Park, Uganda. To identify individuals, they fastened radio collars on a couple of animals in each group, affixed coloured collars on some, and shaved the fur of others in patterns.

Banded mongooses live in packs of 10 to 30 animals, and males outnumber females. Instead of a single breeding pair, each pack has several breeding adults. Almost all females above the age of 12 months have babies, while only a few males get to be fathers.

The most fecund females are older and heftier. When they go into oestrus, the dominant male mongooses guard them for a few days, and aggressively chase away rivals. Despite these precautions, females mate on the sly with other males as well as younger chaps.

And although they mate on different dates, pregnant mongooses give birth together on the same day. This is unusual behaviour for mammals. Overnight, as many as 20 hungry pups have to be fed and nurtured. Parents apparently can’t recognise their babies, and females suckle pups, theirs and others, indiscriminately. This is puzzling because, like our family matriarchs, female banded mongooses appear to have an intricate understanding of who is related. They avoid mating with males of their bloodline and actively seek unrelated males.

Within 10 days of giving birth, adult females go into oestrus again. Dominant males cannot stay at the den and look after pups if they have to jealously guard females while they forage. So the parents go gallivanting, leaving their babies under the watchful eyes of the pack’s bachelors.

Unlike human societies, childcare is exclusively male preserve among banded mongooses. Without such protection, predators such as marabou storks and martial eagles, and rival mongoose neighbours can kill babies.

Once the pups are a month old and start to accompany the pack, each pup forms an exclusive bond with a young male and looks up to him. Often the chaps who babysat the babies become pup-escorts. They teach the youngsters how to find insects, feed them when they beg, and carry their charges away from danger. At the den, the chaperones play with and groom their wards. Such one-on-one bonding between a pup and a young adult is unique in the mammal world.

Although all pups are fed by the group, the ones who have male-nannies grow faster and are more likely to survive to adulthood. Such cooperative behaviour is not unique to banded mongooses. Their closest relatives, meerkats, also raise their packs’ youngsters as a community.

Prof. Cant and his team found that some males consistently help with child care throughout their lives. But some others get away by doing little; they steadfastly refuse to care for pups.

Professor Cant said in a press release, “Over the last 15 years, we have observed how many days each male banded mongoose invests in two different cooperative pup care behaviours. We found that some banded mongooses have strong cooperative personalities and we wanted to find out why.”

Another research project showed caregivers lose weight by taking care of young. Since males less than two years old are unlikely to become breeders, loss of weight doesn’t hurt them. They can always put it on by the next oestrus cycle. Females, however, would pay a price for being skinny. They need to be well-built to be successful mothers. Since they go into oestrus precisely when pups have to be cared for, caregiving doesn’t pay. So males overwhelmingly tend to care for young.

Why do male banded mongooses have such distinct personalities?  Why do some cooperate in raising young, while others don’t? Most of the mongooses in a pack are related. Young males are likely to be uncles, brothers, or cousins. Since the babies are their kith and kin, bachelors help to rear them. This also ensures the size of the group grows. Larger groups have larger territories and access to more food than smaller groups. They can also beat up their neighbours in war.

Despite the additional care provided by their male buddies, many pups do not survive. With so many incentives to help raise one’s own relatives, and even though they don’t lose much, why don’t other males cooperate? Prof. Cant says the reason for the development of these different personalities is unknown.

Sinead English of the University of Cambridge, U.K., who studied cooperative behaviour in meerkats, told The Wire, “Sanderson et al. present some intriguing suggestions, particularly in terms of the underlying mechanism. Perhaps individuals have different metabolic rates and foraging abilities. There is also a need to understand why consistent individual differences in behaviour have evolved. Sanderson et al. suggest that we measure the adaptive benefits of different individual strategies in terms of own offspring produced and also the reproductive output of relatives.”

“We also need to develop new theoretical models to explain why natural selection would result in some individuals specialising as ‘super-helpers’ in cooperative mammals, yet without the division of labour, such as workers and breeders, that is a feature of insect societies.”

Perhaps the lazy sods mistakenly think they stand a chance with the ladies and don’t want to lose weight looking after the little ones. The paper, ‘The origins of consistent individual differences in cooperation in wild banded mongooses (Mungos mungo)’, was published in the journal Animal Behaviour on July 21, 2015.

Janaki Lenin is the author of My Husband and Other Animals. She lives in a forest with snake-man Rom Whitaker and tweets at @janakilenin.