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Thursday, July 26, 2001
The king is a beast, but the queen is a democrat
By ROWAN HOOPER
Imagine a place where all the females give birth at the same time, where grandmothers nurse their daughters' children and baby-sit for them, and where all children are raised in a protective nursery. Where females join together in defending the community against dangerous strangers and those of the same age eat together without squabbling. Sounds rather progressive, almost idyllic, doesn't it?
But these mothers don't wear Birkenstocks. They will fight to the death to protect their territory, and their children, when their teeth are grown, eat freshly killed meat, raw, the blood still warm. This is a place where rogue males may show up and indiscriminately slaughter all the youngsters in the group.
Things like this happen in Tanzania, among lion social groups. Female African lions have a unique system of "plural breeding," whereby pride members consistently produce similar numbers of offspring. Craig Packer and colleagues, of the Department of Ecology, Evolution and Behavior at the University of Minnesota, analyzed data gathered over three decades from several generations of Tanzanian lions and found that, unlike other animal societies in which a dominant female controls the reproduction of her subordinates, lion society is egalitarian.
"Virtually every other carnivore species is strikingly despotic," said Packer in an interview. "In packs of wild dogs, wolves, jackals, coyotes, mongooses or meerkats, there is a single reproductive female, and in spotted hyenas there is a really obnoxious dominant female. Yet the queen of beasts is a democrat."
Lions are the only social cats. Female lions can reproduce at any time of the year, but tend to do so communally. If most other carnivore females are despotic, what's special about lions?
Given that egalitarian species are so rare, studying why they occur is important, not least because a similar underlying egalitarianism might have promoted some of the qualities in human societies that we value.
There are three main differences between lions and other cooperatively breeding birds and mammals, which, say Packer and colleagues in tomorrow's issue of the journal Science, accounts for the egalitarian nature of lion society.
First, in many other species, the young live in a central den or nest, and there they are vulnerable to persecution from the alpha female. Lions -- like other cats -- are highly secretive during the birthing period. Lionesses give birth alone and even hide their cubs from pride members for the first few weeks of life. Secrecy during the first few weeks after birth helps protect the cubs from aggressive males, but also reduces the opportunity for potentially despotic females to cause trouble.
Second, to interfere with another female's young means picking a fight with a fully grown lioness, one of the most formidable natural fighting machines on the planet, 180 kg of muscle, teeth and claw.
"The lions' extensive weaponry carries a greater risk of 'mutually assured destruction' than in other social species," notes Packer. Everyone has seen domestic cats that have been in a tangle with the local tom; the damage is that much worse in lions. "Females will kill each other, but these are gang attacks where one pride goes after its neighbors."
Lions can get irritable when feeding together, "but they generally resolve these disputes without going ballistic," said Packer. Still, he has seen lions with shredded ears as the result of squabbling; blinding is also a risk. Because of this danger, lionesses have quite good manners when they sit down at the carcass to eat. "Owners" of carcasses are respected, and a growl is enough to let a newcomer know that she should eat elsewhere.
Cubs learn lion etiquette early on, as litters are merged to form a creche and cubs nurse mainly from their mother, but sometimes from other females. In a dispute over a nipple between cubs of the same size, the "owner" of the nipple (the one that was there first) usually wins. Rules like this stop disputes from becoming full-fledged fights.
The third reason for the egalitarian nature of lion society lies in the advantages of the nursery system. Cubs have a much higher chance of survival if they grow up in a nursery, looked after by multiple mothers, than if they are raised by their mother alone. This, says Packer, is mainly due to the terrible danger posed if a new male enters the pride. New males have no genetic stake in the pride, so they will often try to kill existing cubs -- forcing females to make another breeding attempt, this time with him.
"Males may be as despotic as warlords," said Packer, "but the females are as egalitarian as soccer moms. They are a true wonder of evolution."
E-mail Rowan Hooper at firstname.lastname@example.org