Previous studies have established ovarian cycle characteristics of adult Asian elephants using progestagen analyses, but little work has been done on young elephants to determine age at puberty. Demographic studies of wild Asian elephants suggest females give birth at about 12–18 years of age (conceiving at 10–16 years of age based on a 2-year gestation). However, there are a few examples of zoo elephants giving birth at only 5–6 years of age, so they would have started cycling much earlier. This study was carried out at the Pinnawela Elephant Orphanage (PEO) in Sri Lanka, where a herd of >80 captive elephants breeds successfully, resulting in a unique opportunity to monitor hormones and document initiation of ovarian cyclicity in young females, thus contributing to the normative reproductive database for this species. We measured serum progestagens in samples collected every 10 days for 18 – 24 months from 11 females (3.5–15 years of age), and found six (5.5 – 12 years of age) already were cycling at study onset. Four females started cycling during the study at 4.5, 5.5, 7.5 and 15 years of age. There were no quantitative or qualitative differences between the first pubertal luteal phase and those of subsequent cycles. Of the 46 ovarian cycles observed, 78% were associated with clear behavioral signs of estrus (heightened bull attentiveness, and willingness of females to be mounted) during the late non-luteal period when progestagens were low. The average body weight at puberty was ~48% of that of adult female elephants at PEO. Asian elephants under human care, including under semi-captive conditions, may reach puberty earlier than those in the wild, perhaps due to better nutrition and reaching a body weight capable of supporting reproductive activity at a younger age. Thus, facilities with bulls need to carefully manage elephants to avoid accidental pregnancies in young females that may be too small to safely carry a pregnancy to term.

中文翻译：

---

斯里兰卡Pinnawala大象孤儿院亚洲雌性大象（Elephas maximus）的青春内分泌相关性

以前的研究已经通过孕激素分析确定了亚洲成年大象的卵巢周期特征，但是对于确定青春期年龄的年轻大象所做的工作很少。对亚洲野生大象的人口统计研究表明，雌性的出生年龄约为12-18岁（根据2年的妊娠，其预期年龄为10-16岁）。但是，有一些例子表明动物园的大象仅在5-6岁时出生，因此它们会更早开始骑自行车。这项研究是在斯里兰卡的Pinnawela大象孤儿院（PEO）进行的，那里成功繁殖了80多头圈养大象，这为监视荷尔蒙和记录年轻雌性卵巢周期的形成提供了独特的机会，从而有助于该物种的标准生殖数据库。我们测量了11位女性（3.5至15岁）在18至24个月内每10天收集一次的血清孕激素，发现已有6位女性（5.5至12岁）在研究开始时就开始骑自行车。在研究期间，四名女性分别在4.5、5.5、7.5和15岁开始骑自行车。在第一个青春期黄体期和随后的周期之间没有数量或质量上的差异。在观察到的46个卵巢周期中，有78％与在孕期低的非黄体期后期发情的明确行为迹象（公牛注意力增强和雌性坐骑意愿）有关。青春期的平均体重约为PEO处成年雌象体重的48％。在人类照管下的亚洲象，包括在半圈养条件下，可能比野生象早到青春期，也许是因为营养更好，并且体重能够支持年轻的生殖活动。因此，拥有公牛的设施需要仔细管理大象，以免年轻女性意外怀孕，因为这些意外怀孕可能太小，无法安全地怀孕。