Spotted Hyena
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The Spotted Hyena, or Laughing Hyena, (Crocuta crocuta) is the largest and best-known member of the hyena family. The Greek root (krokoutas) of its Latin name is used by Pliny the Elder for an unknown animal (possibly hyenas) in Ethiopia; the root translates literally to crocus, commonly used in the ancient world as a yellow dye.
Adult females weigh as much as about 72 kg (158 lb.); they are heavier than the males, which are typically 10 kg (22 lb.) lighter.
Behavior
The spotted hyena is primarily a predator, not a scavenger. Individuals have been clocked at over 55 kilometres per hour (34 mph), and when hunting in packs are capable of taking down the largest of prey. Spotted Hyenas have such formidable jaws (one of the strongest in the animal kingdom) and teeth that they devour even the bones of their kill. This, combined with their very strong stomach acid, results in them having crusty white droppings (from all the bone meal). The hyena's distinctive laughing call, used to disorient prey and gather the pack, has resulted in their nickname "laughing hyena".
Spotted Hyenas live in the savannas and deserts of Africa, in clans averaging 40 individuals - with some as large as 100. Female Spotted Hyenas are larger than their male counterparts, and socially dominant over them. Males leave their natal group on reaching sexual maturity, while females remain in it; the society is highly structured, with dominance relationship between the matrilines (the groups of females descended from a single mother) that endure for generations.
While Spotted Hyenas have no real predators (besides humans), they are on occasion killed by lions, which eat the same foods and will often clash with hyenas over kills. The explanation for this competition is that lions and spotted hyenas are of the same guild. With the development of television cameras that can "see" in the dark, male lions have now been imaged breaking the backs of hyenas. Although lions are much larger, hyenas will defend their kills if possible, and hyena packs have been known to kill lions if they outnumber them significantly. In packs, the spotted hyena is known to take down other even larger animals such as the Blue Wildebeest and the Cape buffalo.
Like many social carnivores, spotted hyenas are playful, especially when young. In captivity they can become very tame, and Europeans living in Africa have sometimes successfully made pets of them.
Reproduction
The female Spotted Hyena's urogenital system is unique among mammals: there is no vagina, and the clitoris is as large and as erectile as the male's penis - only the shape of the glans makes it possible to tell the sexes apart. The female urinates, mates and gives birth through this pseudo-penis (it contracts for mating, the opening widening to admit the male's penis). It was thought that the development of this structure depended on a masculinisation process triggered by the action of androgens on the female fetus, but experiments with anti-androgens show that it still forms in the effective absence of the hormone, so it is now ascribed to normal morphogenesis and sexual mimicry.
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 captivity, many cubs of primiparous mothers are stillborn because of the long labour times involved; in the wild, survival rates of females seem to fall sharply around the age of first giving birth, suggesting that the process is hazardous for the mother also. This suggests that at some point there must have been powerful selective pressures driving the evolution of masculinisation.
Masculinised female genitalia also appears in some lemurs, spider monkeys, and the binturong but the fused vulva is unique to the hyena.
References
- Hyaena Specialist Group (1996). [Crocuta crocuta]. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006.
- [Androgens and the Role of Female "Hyperaggressiveness" in Spotted Hyenas (Crocuta crocuta) Wolfgang Goymann, Marion L. East, and Heribert Hofer (pdf)] - 'Androgen-independent mechanisms are likely to also play an important role, as treatment with anti-androgens during fetal development did not produce females without a pseudo-penis (Drea, Weldele, Forger, Coscia, Frank, Licht, and Glickman, 1998).'
External links
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