||IV. Male Animals Are Not Consistently More Aggressive Than Females||Page 7|
Competitive fighting, which consists of fighting over food under conditions of starvation, is an important type of aggression which may be more pronounced in females than in males. It is apparently a special case of offense. Although the earliest study we published showed no sex differences, more recent data from our laboratory indicates that females have higher levels of competitive fighting than males in the laboratory rat. Our preliminary data indicate that this is due to a specific effect of estrogen on the offense-motivational mechanism. In any case, there is certainly no reason to say that males are more aggressive than females under these conditions.
As a general rule there is no sex difference in predation in those species in which this non-social form of aggression is found. This is the case not only in carnivores, but in other mammals. There is, for example, no sex difference in the mouse-killing behavior of rats.
Defense, as opposed to offense, is a type of aggression used against predators and other threatening species as well as against threatening animals of the same species. As a rule there is no sex difference in defense among most mammalian species. This is especially true for the biting defensive attack. Some might claim an exception in the greater tendency for male rats to show boxing in response to footshock, but I believe that this reflects the size differential of males and females, and is easily controlled by testing males and females in differing cages of a size proportional to body size.
In sum, we may conclude that female mammals are as aggressive as males, unless one narrows the focus to only one particular type of aggression or only one type of laboratory condition. In the broad view, it turns out that certain types of aggression are more pronounced in males, other types more pronounced or exclusive to females, and other types common to both sexes. In any case there is no support here for the myth that humans have inherited a general mammalian tendency for males to be more aggressive than females.
(End of chapter)