The Spotted Hyena (Crocuta crocuta) is a predatory mammal, closely related to civets and mongooses, and are found throughout sub-Saharan Africa. Their lifespan in the wild extends to about 25 years, and they generally weigh from 110-190 pounds. [7,9] They live in clans of up to 90 members, of unrelated males and closely related females. The clans are female dominated and rank is inherited along maternal lines. Spotted Hyenas show great social complexity that is comparable to primate societies. However, perhaps the most remarkable characteristic of the Crocuta crocuta, not seen at all in the other two species of hyena, is the hyper-masculinization of the females. Spotted Hyena females are about ten percent larger than the males, and are considerably more aggressive. Females also have an enlarged clitoris that is fully erectile, with labia that are folded over and fused in such a way that resembles a scrotal sack. Thus, the external genitalia are difficult to distinguish between genders, although it has been noted that the male genitalia is slightly thinner and longer. Female spotted hyenas urinate, mate, and give birth through a hole in this pseudo-penis. The internal organs of the females are similar to what is found in most other female mammals, except that there is a hairpin turn in the urogenital canal that goes through the enlarged clitoris.[1] This leads to difficulty in giving birth, such that there is a significant chance of mortality in first time mothers. The pseudo-penis also a part of social interactions. [5].
Currently there are two contending categories of hypotheses concerning the nature of the spotted hyena pseudo-penis. The adaptive hypothesis is currently the stronger of the two and what will be more thoroughly discussed in this review. The second hypothesis states that the pseudo-penis is a side of effect of other adaptations that contributed to their other "masculine " traits, such as large body size and aggressiveness.