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Reproduction
The female Spotted Hyena's urogenital system is unique among mammals; the female's clitoris is elongated to form a fully erectile phallus, and the vaginal opening is at the tip of this phallus. Only the shape of the
glans at the tip of the phallus makes it possible to differentiate the sexes. The female urinates, mates and gives birth through this
pseudo-penis. Since it is impossible to penetrate without the female's cooperation, female hyenas have full control over whom they choose to mate with. The male hyena's penis lacks a
baculum, a bone found in the genitals of most mammals.
Birth is very difficult: the internal birth canal extends almost to the subcaudal location of the
vulva (which in Crocuta is fused to form a
scrotum containing fatty pseudo-testes) before turning abruptly towards the clitoris, and the clitoris itself is narrow (although it ruptures with the first
parturition, making subsequent births easier). In a female giving birth for the first time the pseudopenis may tear as much as 15cm along its length to accommodate the passage of the baby.
[13] In captivity, many cubs of first time mothers are stillborn because of the long labour times involved, and in the wild, it is estimated that 10% of first time mothers die during labour.
[14] Spotted hyenas usually have 2 cubs at a time and they are raised for about 10 months.
Researchers originally thought that one of the things that causes this characteristic of the genitals is androgens that are expressed to the fetus very early on in its development. However, it was discovered that when the androgens are held back from the fetus, the development of the female genitalia was not altered. Other hyena species lack this adaptation, making it a fairly recent one in the hyena line. Masculinised female genitalia also appears in some
lemurs,
spider monkeys, and the
Binturong but the fused vulva is unique to the hyena.
Hyenas are born with their eyes open and teeth already fully developed after a 4 month gestation period. At birth, the cubs weigh 1 to 1.6 kg (2.2–3.6 lb), and are among the few mammals to commit neonatal
siblicide. A same sexed litter will result in vicious fighting between the cubs, often resulting in death. This siblicide is estimated to contribute to 25% of hyena cub mortality.
[15] Since a single cub will receive more food and mature faster, this behavior is probably adaptive. Spotted hyena milk is very rich, having the highest protein content (14.9%) of any terrestrial carnivore, and the fat content (14.1%) is second only to the
polar bear, so unlike lions and wild dogs, they can leave their cubs for about a week without feeding them.
[16] Two to six weeks after
whelping, young are transported to the communal den. Young depend entirely on milk for about 8 months and are not weaned until 12 to 16 months old. Maturation is at three years, females later than males. Female offspring remain in their natal clan while males leave at around two years.
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Hyenas have
extremely strong jaws in relation to their body size. In 2005, Dr.
Brady Barr of the
National Geographic measured the bite forces of many different animals, including spotted hyenas for the documentary
Dangerous Encounters: Bite Force. A
one year old cub had a bite measured at
603 pounds-force (2.68 kN), leading to the postulation that a
full grown adult could bite at over
1,000 pounds-force (4.4 kN).
[9] This mandibular power, combined with its large pyramid shaped molars allows it to easily crush bone, even those of
elephants.
[10] An experiment conducted in 1955 showed that the
spotted hyena easily outclassed the much larger brown bear in bone crushing ability.
[11] It is often asserted in television and print that hyenas have the most powerful bite for their overall body mass when compared to other animals, although there is no scientific basis for this claim
Vocalizations
The spotted hyena is among the most vocal African mammals, with over 11 different sounds being recorded.
[24]
- Groans/soft squeals – Often exchanged during greeting.
- Whoop – A contact call, varying in pitch and intensity. A fast whoop is a rallying cry given by excited hyenas during conflict or at a kill site. Apparently, calls emitted by males are usually ignored. Calls emitted by females however are responded to immediately.
- Lowing – A sound made by impatient hyenas, usually when waiting for their turn at a kill.
- Grunting – A very low growl with the mouth closed that accompanies aggressive behaviour.
- Growling – A deep, resonating rumble made by defensive hyenas threatening to bite.
- Rattling growl – A low-pitched, soft, staccato grunt given as an alarm call.
- Giggling – A high pitched, cackling laugh, typically emitted by hyena being chased; expresses intense fear.
- Yelling – A roaring scream voiced by hyenas attempting to escape attackers.
Attacks on humans
While hyenas, in general, do not hunt humans, some attacks have occurred and have even caused human death.
[30][31] Spotted hyenas are widely feared in
Malawi, where they have been known to occasionally attack people at night, particularly during the hot season when people sleep outside. Hyena attacks were widely reported in Malawi's
Phalombe plain, to the north of
Michesi Mountain. Five deaths were recorded in 1956, five in 1957 and six in 1958. This pattern continued until 1961 when eight people were killed. Attacks occurred most commonly in September, when people slept outdoors, and bush fires made the hunting of wild game difficult for the hyenas.
[32]
