Far from evil, cackling scavenger-label spotted hyaenas are a curious and remarkable species, and one which defies any sexist gender-role expectations. Female spotted hyaenas leave the males with no doubt as to who is in charge.
Spotted hyaenas are territorial hunter-scavengers, living in large, female-dominated clans that can consist of up to 80 individuals. Females are larger than the males and will stay with their natal clan while the smaller, subordinate males leave the clan after a couple of years.
Socially organised much like that of old world monkeys, a group that includes baboons and macaques, spotted hyaenas are able to recognise individuals within their clan and will cooperate or compete depending on their relationship. Female dominance is regularly asserted by aggression, however higher-ranking females maintain their rank by allying with those they have formed good relationships. This reduces the need for dangerous altercations.
Rank within the clan is nepotistic, with female cubs inheriting their status from their mothers, while even the most dominant of males are still subordinate to the lowest-ranking females. Passivity in males is rewarded with greater success in mating.
Female spotted hyaenas have an extraordinary pseudo-penis which is an elongation of the clitoris and is almost indistinguishable from the male's penis, both being around the same length, erectile and have spines present. The urethra and vagina exit through an opening that extends the length of the pseudo-penis, which allows for copulation, birth and urination.
The vagina is blocked by the enlarged clitoris and false scrotum made from fused labia, making the spotted hyaena the only mammal without an external vaginal opening. This makes the mating incredibly complicated and the male's penis needs to be carefully and expertly inserted into the female's vagina through her partially-retracted pseudo-penis, a process that can take months of experience to perfect.
Giving birth is also problematic as the cub needs to exit via the narrow clitoris, which regularly ruptures at the tip during the process. In some instances where the umbilical chord does not stretch far enough or the pseudo-penis does not split the cub may suffocate. This means that firstborn mortality can be as high as 60% while one in every 10 females die whilst giving birth for the first time.
In the womb, developing spotted hyaenas are provided with androgen, a steroid hormone that develops male characteristics in vertebrate animals. This supply encourages the behavioural and muscular masculinisation of the females, although it doesn't explain pseudo-penis development as this commences before androgen is delivered.
More dominant females supply a higher concentration of androgen than their lower-ranking fellows, meaning that the cubs of dominant females are born much more aggressive and sexually charged.
The reason for this apparent gender-reversal could be explained by the increased aggressiveness as a selective advantage for this stocky hunter-scavenger. Spotted hyaena mothers are solely responsible for their young and in groups where a large number of animals may surround one kill, it pays to be the offspring of a powerful and dominant mother.
The pseudo-penis could also be a winning below in the sexual arms race that is a constant battle between males and females of each species. Throughout the animal kingdom, males and females compete in order to guarantee the continuation of their genetic line, and as such a number of adaptations have arisen in order to dissuade cheats. One of these adaptations appears to be the female spotted hyaena's lack of external vagina which removes the ability of males to sexually coerce and rape females. This immediately allows the females to dominate mate selection.
It is unclear which of these theories is the main reason, it is probably a mixture of the two (or perhaps neither!), but either way we can all agree it has provided confirmation, the female of the species is perhaps more deadly than the male. In spotted hyaenas at least.