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Musth
Musth or must is a periodic condition in bull (male) elephants, characterized by highly aggressive behavior and accompanied by a large rise in reproductive hormones. Testosterone levels in an elephant in musth can be as much as 60 times greater than in the same elephant at other times. However, whether this hormonal surge is the sole cause of musth, or merely a contributing factor, is unknown; scientific investigation of musth is problematic because even the most placid elephants become highly violent toward humans and other elephants during musth, requiring segregation and isolation until they recover. Female elephants do not undergo musth.
==Cause and effects==
Although it has often been speculated by zoo visitors〔http://www.upali.ch/musth_en.html〕 that musth is linked to rut, it is unlikely there is a biological connection because the female elephant's estrus cycle is not seasonally-linked, whereas musth most often takes place in winter. Furthermore, bulls in musth have often been known to attack female elephants, regardless of whether or not the females are in heat. There has been speculation that musth is connected to natural periodic reorganization of dominance among males in elephant herds.
Often, elephants in musth discharge a thick tar-like secretion called temporin from the temporal ducts on the sides of the head. Temporin contains proteins, lipids (notably cholesterol), phenol and 4-methyl phenol,〔Physiological Correlates of Musth: Lipid Metabolites and Chemical Composition of Exudates. L.E.L Rasmussen and Thomas E Perrin, Physiology & Behavior, October 1999, Volume 67, Issue 4, Pages 539–549, 〕〔Musth in elephants. Deepa Ananth, Zoo's print journal, 15(5), pages 259–262 ((article ))〕 cresols and sesquiterpenes (notably farnesol and its derivatives). Secretions and urine collected from zoo elephants have been shown to contain elevated levels of various highly odorous ketones and aldehydes. The elephant's aggression may be partially caused by a reaction to the temporin, which naturally trickles down into the elephant's mouth. Another contributing factor may be the accompanying swelling of the temporal glands; this presses on the elephant's eyes and causes acute pain comparable to severe root abscess toothache. Elephants sometimes try to counteract this pain by digging their tusks into the ground.
Musth is linked to sexual arousal or establishing dominance, but this relationship is far from clear. Cases of elephants goring and killing rhinoceroses without provocation in national parks in Africa have been documented and attributed to musth in young male elephants, especially those growing in the absence of older males. Studies show that reintroducing older males into the elephant population of the area seems to prevent younger males from entering musth, and therefore, stop this aggressive behavior.〔("Killing of black and white rhinoceroses by African elephants in Hluhluwe-Umfolozi Park, South Africa" ) by Rob Slotow, Dave Balfour, and Owen Howison. ''Pachyderm'' 31 (July–December, 2001):14–20. Accessed 14 September 2007.〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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