From ancient Roman naturalists to modern writers such as Ernest Hemingway, people have struggled for thousands of years to tell the difference between the male and female hyenas. All kinds of different explanations for the hyena’s anatomy have flourished, some based on myth, others based on sober scientific understanding. There are four different species in the hyena family. Three of the four, including the spotted hyena, the brown hyena, and the aardwolf, are all found in sub-Saharan Africa, while the striped hyena is endemic to both northern Africa and Asia. Of all four species, only the spotted hyena has a matriarchal society in which all female members rank higher than the males, giving them greater access to food and resources (the females form their own ranking from the most to least dominant too). This matriarchal society also comes with significant physical changes that set them apart from all other mammalian species and make hyena births very difficult. So, how do hyenas give birth and what makes it so unique? Keep in mind that this article will have some very detailed descriptions of hyena anatomy, reproduction, and the birthing process. The spotted hyena will be the main focus unless otherwise mentioned.
What is so unique about the female hyena’s reproductive anatomy?
What makes the female hyenas so interesting is that they do not have a typical vaginal opening; instead, their reproductive organ looks like male genitalia. The name of this strange structure is the pseudo-penis. It looks almost exactly like you would expect from a real penis. It’s even capable of getting an erection. But while it may superficially resemble the male genitalia, the pseudo-penis is actually just an enlarged clitoris (a vestigial structure present in just about all mammalian female bodies) that can be retracted back into the abdomen when not in use. The normal vaginal opening is fused together into a fake scrotum that doesn’t really serve much of a purpose. Internally, the female anatomy looks mostly as you would expect. There’s the typical hyena birth canal and uterus like all other females. Her body also produces normal eggs that must be fertilized by sperm. But the pseudo-penis does introduce several anatomical complications. The female must do all of her normal business out of it, including such functions as female copulation, urination, and birth. Two of these functions obviously hadn’t evolved with the penis in mind. This requires some unusual adaptations, which will be covered below. While many mammalian species have a fake penis for display purposes (including some moles and lemurs), the spotted hyena is the only one with this unusual penis-clitoris configuration. Not even its closest living hyena relatives have anything quite like it. Additionally, Hyenas are considered to be fantastic mothers. Hyenas are one of the few animals in the animal kingdom that spends a surprising amount of time nurturing their young. Hyenas give birth to 1 to 3 cubs or pups that are born with teeth and their eyes open. Hyenas are close cousins to cats, so it’s interesting to note that cats are born blind and helpless.
Why did the hyena evolve such unique anatomy?
It’s not entirely clear why evolution would favor this anatomy, but one possible answer is that the development of the pseudo-penis is a byproduct of other changes in the female’s body that make them more aggressive and dominant. These unusual changes begin shortly after the hyena is conceived in the womb. Female spotted hyenas (unlike female striped hyenas or brown hyenas) are exposed to very high levels of the male-specific hormone testosterone, which allows them to become more muscular; the female is actually the larger of the two sexes, enough to challenge and even surpass the males for dominance. Dominant, high-ranking females will also give their developing offspring, both males and females, higher levels of the hormone androgen compared with lower-ranked mothers. Androgen is associated with higher dominance and social status. Essentially, the dominant females are “passing down” the high ranking to their offspring to their children. Why would female hyenas need to be just as aggressive and muscular as the males? One explanation may be related to the feeding strategy of the hyena clans. Spotted hyenas (unlike even the striped and brown hyenas) eat together as a group. More than 20 individuals may have access to a single kill; sometimes the entire carcass can disappear into a swarm of mashing teeth within a matter of minutes. Dominance hierarchies usually determine the order of their feeding: the alpha female and her offspring eat first, then the less dominant females and their offspring feed, and finally the males eat last. But not everyone is assured of having enough to eat. Scientists have hypothesized that the female’s extra aggressiveness and musculature give them the ability to dominate resources over both males and weaker females in an otherwise highly competitive feeding situation. This gives priority to her offspring as well, ensuring that the most dominant members of the next generation are well fed and cared for. According to this hypothesis, the “end goal” of evolution in this case was to make more dominant female hyenas. The pseudo-penis is simply a byproduct of greater exposure to male chemicals in the womb and not really the goal onto itself. That doesn’t rule out the possibility that the pseudo-penis has its own important uses. Scientists have suggested there is pressure for females to appear like males because dominant females have the tendency to kill the female offspring (and therefore potential competitors) of lower-ranked females to give their own offspring an additional advantage. This would mean the pseudo-penis is an advantage for lower-ranked female offspring to literally avoid the wrath of the alpha female. After all, it is obviously harder for dominant females to target and kill younger offspring if they have a pseudo-penis that looks exactly like a male. Indeed, the female’s development would seem to favor this explanation. Male and female hyenas are basically indistinguishable from each other, except at a molecular level, immediately after birth. The two sexes only become more anatomically distinct as they age.
How does the hyena mate?
Spotted hyena reproduction can actually take place at any time of the year, but peak mating usually occurs in the wet season, when it’s most likely to rain. Males will make a bowing display to the female and immediately back off if she shows any signs of aggression. If she accepts his offer, then the female essentially has the ability to retract the pseudo-penis and allow the male to enter. It still takes some awkward positioning on the part of the male to mount her correctly, which means he will probably need months of practice before his first attempt. The sons of the alpha female usually have the best chances of succeeding on their first attempt; because they’re been exposed to extra androgen in the womb compared to lower-ranked offspring, they are generally more aggressive and will start practice mounting at a few months of age, making them well-prepared for the real thing. A single female may have multiple mating partners every year.
How do hyenas give birth?
The birthing process is where the downsides of the pseudo-penis genitalia become most apparent. As mentioned previously, the entire structure of the hyena birth canal is highly modified to account for the unusual quirks of the pseudo-penis. After the eggs are fertilized, the offspring gestate in the uterus for a few months like normal. However, when she is ready to give birth, the mother essentially needs to squeeze a 2-pound cub through a narrow opening in the hyena birth canal that’s only about an inch in diameter. The problem is compounded by the fact that spotted hyena cubs are among the largest offspring in relation to the mother’s weight throughout the entire animal kingdom. Needless to say, this means hyena births can cause severe tearing that may take weeks to properly recover from. It might be the most traumatizing and difficult birthing process in the entire animal kingdom. Death rates are exceptionally high for both mothers and cubs. Mothers will sometimes bleed to death from the rupture of their reproductive organs, while the cubs will easily suffocate on their way out. First-time mothers will often have the highest death rates; they rarely produce viable cubs on their first attempt. Despite these high death rates, hyenas manage to produce very healthy population numbers. They can bear a litter of anywhere between one and four cubs at a time, although twins are the most likely outcome. If the cubs are of the same sex, then they will sometimes fight violently to the death. This ensures more food for the stronger sibling. The mother produces a new litter every 11 to 21 months before mating again. The alpha females generally have younger ages of first reproduction, shorter hyena birth intervals, and increased survival chances for their offspring.
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