Lincoln G A, Ratnasooriya W D
MRC Reproductive Biology Unit, Centre for Reproductive Biology, Edinburgh, UK.
J Reprod Fertil. 1996 Sep;108(1):107-13. doi: 10.1530/jrf.0.1080107.
Testosterone concentrations were measured in blood samples collected weekly over a 5 year period from six adult (19-40 year old) male Asian elephants (Elephas maximus maximus) living in captivity in Sri Lanka (7 degrees N), to investigate the relationship between androgen secretion and the occurrence of musth (temporal gland secretion, drip urination and aggressive behaviour). The testosterone profiles were very variable both within and between animals. Long-term phasic changes in blood concentrations of testosterone, associated with periods of musth, occurred in three of the six elephants, with the most pronounced cyclicity in the oldest animal. Musth occurred annually after periods of high androgen secretion and there was a positive correlation between the duration of musth and mean concentrations of testosterone during the previous 2 months. The time of musth, while consistent for an individual, was variable between animals. In four bulls living within one social group, there was a positive correlation between social rank and mean concentrations of testosterone over the 5 year study, and only the dominant animal showed periodic musth. Short-term changes in testosterone concentrations occurred in blood samples collected every 15 min for 7 h, and following the injection of 20 micrograms GnRH, consistent with regulation through the pulsatile secretion of LH. Overall, the results support the view that fully mature male Asian elephants living near the equator express an asynchronous, cyclical, circannual pattern of gonadal activity, with the cyclical pattern developing progressively from 20 to 40 years of age. The periodic increase in testosterone secretion during the gonadal cycle induces the development of musth; however, androgen withdrawal following a period of hypersecretion may be the cause of some aspects of musth behaviour (aggression, unpredictability, disobedience) which make bull elephants very difficult to manage in captivity.
对生活在斯里兰卡（北纬7度）圈养环境中的6头成年（19 - 40岁）雄性亚洲象（印度象指名亚种），在5年时间里每周采集的血样进行睾酮浓度测量，以研究雄激素分泌与狂暴状态（颞腺分泌、滴尿和攻击行为）发生之间的关系。睾酮水平在个体内和个体间差异很大。6头大象中有3头出现了与狂暴期相关的睾酮血浓度长期阶段性变化，最年长的大象周期性最为明显。狂暴状态在雄激素分泌高水平期后每年出现一次，且狂暴期持续时间与前两个月睾酮平均浓度呈正相关。个体的狂暴时间虽具有一致性，但不同个体之间存在差异。在一个社会群体中的4头雄象中，在为期5年的研究中，社会等级与睾酮平均浓度呈正相关，只有占主导地位的个体表现出周期性的狂暴状态。每隔15分钟采集一次血样，共采集7小时，并在注射20微克促性腺激素释放激素后，睾酮浓度出现短期变化，这与通过促黄体生成素的脉冲式分泌进行调节一致。总体而言，研究结果支持以下观点：生活在赤道附近的成年雄性亚洲象表现出一种异步、周期性、年度性的性腺活动模式，这种周期性模式在20到40岁之间逐渐形成。性腺周期中睾酮分泌的周期性增加会引发狂暴状态的发展；然而，高分泌期后的雄激素撤退可能是导致狂暴行为某些方面（攻击性、不可预测性、不顺从）的原因，这使得圈养中的雄象极难管理。
