The battle for breeding rights in the animal kingdom is almost always associated with the males of a given species, not the females. Whether its two bull elks locking antlers in the Canadian wilderness or two douchebags hinting at their incomes in a night club, we usually consider the fight for reproductive opportunities to be a masculine one. However, researchers suspect that this type of competition between females may be just as active, if not as apparent.

One reason we don’t have an immediate image for female competition is that is usually takes a far more subtle form. In a special issue of Philosophical Transactions of The Royal Society B, Paula Stockley and Anne Campbell point out that just because male forms of competition are more visible – peacock tail feathers, moose antlers, Jersey Shore blow-out hair cuts – that doesn’t mean they are the only ones trying to nudge same-sex competitors out of the picture. At present we have years of data suggesting that female aggression has played an equally crucial role in the sexual selection, and thus the ultimate evolution of a given species.

Breeding rites are often associated with such male-centric confrontations such as this contest between two bighorn rams. This particular battle can also take place between man and ram when Mountain Dew rights are at stake.  (Steve Price)

Females of social species will also form complex hierarchal systems in which subordinate females will share the responsibility of raising an alpha female’s young. By intimidating other females into raising her young, an alpha can have more offspring, and thus plug more of her DNA into the gene pool. These communal child rearing groups are basically the animal version of The Babysitter’s Club, except that if you don’t show up to babysit for the McCarthy twins, you’ll be exiled to the open savannah, where you’ll likely starve to death.

Females don’t just display a spike in aggression when they are looking to breed; There is also a significant spike in aggression once their children are born and need to be defended. The catalyst for this second stage of female beast mode may be due to increased levels of oxytocin. Oxytocin is often called the “motherly love hormone,” which spurs mother-child bonding, but it can also serve as a “motherly hate for hungry predators” hormone as well, since it causes an aggressive defense reaction toward potential threats to her young.

Long known for their hunting ability, female wolves can also show another form of aggression when subordinating other females to help raise to help raise their young. (Richard Seeley/National Geographic)

One reason the forms female aggression are less dramatic may have to do with the expenditures they will have to make once they are fertilized. Usually playing a minor role in the rearing of their young, males can afford to direct more physiological resources toward growing massive horns for sparring or traveling long distances just to pick a fight. Females, however, can’t afford to spend three weeks being an abrasive asshole to everyone they see, since in a matter of months they will soon be carrying a child and thereafter protecting it.

Hyenas represent one of the few species for which females will directly engage with each other. (NatGeo)

Can we observe any of these alternative forms of aggression in human females or have societal and cultural norms eclipsed these biological phenomena? Will you be better about leaving the toilet seat down now that you know your girlfriend could be supercharged with oxytocin at any given time?

Source: DiscoveryNews