Johannesburg - Testosterone has a long rap sheet. It is the driver behind many violent crimes, but in one society it is the unlikely glue that holds everything together.
The testosterone-fuelled, over-aggressive leader in this society is not male. It is a matriarch and she rules with her teeth, claws and dollops of fear.
Scientists working in the Kalahari desert have found that testosterone appears to play a crucial part in cooperation in meerkat societies.
In these clans the boss is the matriarch, who, with her mate, rules over a group of subordinate females and males.
What keeps her in charge, the researchers found, are very high levels of testosterone.
In meerkat society only the matriarch breeds and it is the subordinates who help raise her pups.
And it is here where the aggression comes in. To ensure her underlings care for her pups, she will attack pregnant subordinates even going so far as expelling them from the group or killing their offspring.
The matriarch’s reign of terror will include her dominating others through pushing, shoving, biting and growling.
“We always think of male competition being driven by testosterone, but here we are showing that it is driving female competition, too,” Christine Drea, professor of Evolutionary Anthropology at Duke University, said in a statement.
The research team worked with 22 clans of meerkat at the Kuruman River Reserve in the Kalahari Desert. Their study appeared this week in the journal, Nature Communications.
To monitor testosterone levels, they collected blood and faeces while making careful observations of the matriarch’s behaviour during her pregnancies. They would note when she was being particularly aggressive.
“In non-pregnant matriarchs, testosterone values are equivalent to the males’, and just a little bit lower in subordinate females. But when matriarchs get pregnant, they ramp up,” said Drea.
The matriarchs’ heightened aggressiveness corresponded with increases in testosterone levels as her pregnancy progressed.
It was found that after birth, her pups were also aggressive, demanding care and feeding from the subordinates.
To work out if testosterone was the cause of this aggressiveness and if it helped the matriarch keep her spot as the ruler of the clan, the researchers conducted an experiment.
They treated some of the matriarchs with flutamide, a testosterone-receptor blocker that prevents the hormone from acting. The matriarchs, treated with flutamide, became, well... soft. They didn’t shove, bite or growl as much, and her subordinates picked up on this. They weren’t as obedient.
Her pups behaviour also changed. Without the testosterone booster they got in their mother’s womb, they too became less aggressive and more calm.
The scientists had found that, ironically, testosterone assists with the mothering and raising of meerkat pups.
Testosterone helps matriarchs have more pups and gives those offspring a great start in life by enabling them to bully the subordinates.
“Females are not primarily competing for food,” she said. “Competition is about ensuring that other individuals help raise their kids. And testosterone helps them win that reproductive battle,” Drea said.