Endocrine correlates of puberty in female Asian elephants (Elephas maximus) at the Pinnawala elephant orphanage, Sri Lanka

Abstract

Background: 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. Results: 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. Conclusions: 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.

Seasonal Effects on Body Condition and Characteristics of the Estrous Cycle in Captive Asian Elephants (Elephas maximus) in Thailand: A Retrospective Study

“…The remaining data were defined as the baseline. In a previous study, serum progesterone concentrations from Asian elephants ranging from 0.94 to 4.71 ng/mL (>3.99 ng/mL) were detected by using the same EIA protocol [ 34 ]. However, the maximum detectable value of EIA in this study was 3.99 ng/mL.…”

“…Asian and African elephants are thought to live for more than 70 years [ 31 , 32 ], and most females can continue to reproduce until the age of 60 [ 27 ]. Given these considerations, throughout the long lives of female elephants, the regular monitoring of blood progesterone is an important tool in the strategies and management of breeding in order to (1) monitor gestation to avoid stillbirth and predict the delivery time and ovarian cycle patterns [ 33 ]; (2) avoid unexpected pregnancies around the early puberty period [ 34 ]; (3) determine the optimal time for mating and control the management of females of prime breeding age (before 30 years of age) and old females management [ 8 , 35 ]; (4) diagnose pseudopregnancy by identifying the prolonged duration of the luteal phase [ 34 ], etc. Furthermore, determining whether elephants have a normal ovarian cycling status requires managers to know and calculate the baseline progesterone.…”

症例報告：アジアゾウ（<i>Elephas maximus</i>）の子ゾウ2頭における離乳前後の血中骨代謝マーカー値

“…It is known that bone metabolism is regulated by the endocrine system, with the effects of estrogen in particular being extensively studied [22]. However, for Asian elephants, it is known that the adolescent cycle, which involves dynamic changes in sex hormones including estrogen, begins for the first time between the ages of 4.5 and 7.5 years [23]. Although it is unlikely that the endocrine system, including estrogen, had a significant impact on bone metabolism in the test animals of this study at the age of 2.6 and 2.5 years, there is still room for further investigation into their effects in the future.…”