Fat means fate for meerkats, according to a study published Wednesday in the journal Nature. In a mob or colony, only a pair of parents are allowed to breed and the only way to achieve that dominant status is by becoming the fattest and heaviest female of all.
These mammals are known for living in a unique cooperative society, but researchers have discovered how fierce the competition is to be able to reproduce and the inequality the system is based on.
University of Cambridge behavioral ecologist Tim Clutton-Brock said female meerkats can give birth up to 81 pups in their lifetime. However, they must work really hard to gain such a privilege if they don’t want to be invisible during the rest of their lives.
The species live in mobs of up to 50 that keep watch for predators, fend off any invading snakes and babies are raised communally. But it works because all the females who aren’t alpha are resigned to babysit the dominant mom’s offspring unless one of them gets to replace her once she dies or by gaining more weight than her.
“There’s very strong selection on females to get to the breeding position and they consequently compete like hell to get there,” Clutton-Brock said, as quoted by The Washington Post.
Fat is power
Every female in the group is constantly trying to gain weight in order to become the largest and fattest to be allowed to reproduce, which results in a never-ending competition. Meerkats are highly sensitive to one another’s weight and always try to modify the number of calories they consume based on the growth of the other candidates around them.
The competition never ends because the group’s alpha female must carefully maintain her physical authority to prevent others from displacing her. Once she ascends to the breeding position, she eats basically everything she can during three months in order to keep being the fattest. Her effort is particularly strong when the next-fattest female is coming closer to her size.
The study
Clutton-Brock has been closely studying wild meerkats in the Kalahari desert of southern Africa for the last 24 years. His team recognizes every single individual in more than 60 mobs.
Study co-author Elise Huchard from the University of Cambridge chose 14 of these colonies and selected some of the smaller and younger meerkats, who were fed by the research team twice a day for three months with half a hard-boiled egg. These individuals were described as “the challengers.”
The study found that larger individuals who had to find food by their own, noticed that the challengers were getting fatter and started eating much more in order to maintain their social status. The study authors wrote in the paper that the growth of nearly all siblings was proportional to the growth of their fed challengers by the end of the experiment.
Scientists are yet to determine the methods meerkats use to monitor the weight of their competitors but they already know their sense is impressively accurate since they don’t simply eat more all the time regardless of what happens around them. Huchard pointed out that meerkats are the target of many predators and are careful to spend too much time foraging and digging.
Inequality
The dark side of life among meerkats is based on inequality. Dominant females breed like crazy and the fact that everyone else is forced to take care of their pups allows them to have time to fiercely defend their status.
Meerkat moms have different methods to ensure that only their descendants will survive. They eat the younger breed of other meerkats and sometimes annoying subordinates end up being exiled from the colony to face the merciless desert on their own.
In other cases, alpha females teach young meerkats to eat venomous scorpions alive.
As for males, their efforts are focused on displacing the alpha of other groups and take over from the deposed rather than trying to become the head of their own mobs.
There are other species whose social system works similarly but it’s less conflictive because it works the other way around. In coral globes, for example, subordinates eat less to prevent themselves from reaching the size of dominant individuals. They prefer to avoid getting in trouble.
What to study next
Huchard and her research team want to study the costs of eating too much regardless of the growth of competitors in terms of health risks. They’re also interested in being able to measure the hormone levels of meerkats to discover whether unfed individuals experience changes that determine their growth rate regardless of the amount of food they consume.
Some hints of this were found as subordinate meerkats finally reached the dominant status and grew faster during the few months after becoming the alpha females, even when they didn’t make any effort to get bigger.
Source: Washington Post