1. During the course of an eight year field study of African elephants in Amboseli National Park, Kenya, from September, 1972 to December, 1980, females were seen exhibiting oestrous behaviour on 154 occasions, during which 43 copulations were witnessed. 2. Five categories of oestrous behaviour are described: a) wariness, b) the oestrous walk, c) the chase, d) mounting, and e) consort behaviour. 3. The oestrous behaviour as described was found to be temporally associated with ovulation, as judged by conceptions, in 70.7% of 58 cases. 4. The duration of oestrous periods is estimated at 2-6 days. 5. On average Amboseli females conceived once every 5 years and for each of these conceptions the female may only have been in oestrus once. 6. Evidence from the Amboseli study suggests that some females may exercise choice in mating partners. For example, females were able to elude their pursuers in 69.4% of all chases (n = 134). Observation of female behaviour during oestrus suggested that some females preferred to mate with males in the largest size class, particularly those in musth. 7. Two possible short-term advantages to females exercising choice in mating partners are suggested: a) avoidance of harassment from other bulls; and b) Large males in musth may be more likely to impregnate a female. 8. A possible long-term advantage to mating with a Large, and therefore older, male could be his ability to pass on a trait for longevity. 9. Although females may be exercising choice among the size/age classes, male-male competition among the Large males may override female choice on the individual level.

Oestrous Behaviour and Female Choice in the African Elephant

Considerable information now is available about the basic reproductive biology of elephants, especially females. However, as important as this knowledge is, it no longer is enough to simply compile it into a database. The potential exists for using endocrine monitoring techniques to solve real problems. This review summarizes our current knowledge of elephant endocrinology and offers suggestions on how to use the technology to maximize reproductive potential. The estrous cycle can be monitored through the analysis of serum progestogens, primarily 5α-reduced compounds, and consists of an 8- to 12-week luteal phase and a 4- to 6-week inter-luteal period. Proof of ovarian cyclicity currently is mandatory before Species Survival Plan breeding recommendations are approved. However, because many adult females are not cycling normally, the reproductive monitoring of all cows throughout their life span is now encouraged. Complete endocrine evaluations in conjunction with ultrasound examinations and behavioral assessments are needed to identify causes of reproductive failure and develop mitigating treatments. Progestogen analyses also are effective for monitoring pregnancy, but only if longitudinal samples are collected. Alternatively, pregnancy can be diagnosed in occasional samples using serum prolactin or possibly relaxin measurements after 20 weeks of gestation. Parturition can be predicted on the basis of the rapid decrease in progestogens that occurs about 2–5 days before birth. An updated model of ovarian dynamics during the estrous cycle suggests that two waves of follicular development occur 3 weeks apart during the non-luteal phase, possibly under the control of follicle-stimulating hormone. Each follicular wave culminates in a luteinizing hormone (LH) surge, with the second surge inducing ovulation and corpus luteum formation. The functional significance of the first, anovulatory LH surge is under investigation, but from a practical perspective it can be used to schedule breeding (by artificial insemination or natural mating) to coincide with the ovulatory LH surge. Less is known about the reproductive biology of bulls, aside from the fact that musth is associated with dramatic changes in androgen secretion. Studies are needed to determine whether poor libido and inadequate semen quality observed in some mature elephants are due to testicular steroidogenic dysfunction. When blood samples cannot be collected for routine hormone analysis, gonadal activity can be monitored non-invasively through the measurement of excreted steroid metabolites (males: androgens; females: estrogens, progestogens) in urine and feces. Lastly, suggestions for future research priorities are provided. Zoo Biol 19:347–367, 2000. © 2000 Wiley-Liss, Inc.

Reproductive endocrine monitoring of elephants: An essential tool for assisting captive management

Excretory fate of estradiol and progesterone in the African elephant (Loxodonta africana) and patterns of fecal steroid concentrations throughout the estrous cycle.

In the elephant, two distinct LH surges occur 3 wk apart during the nonluteal phase of the estrous cycle, but only the second surge (ovLH) induces ovulation. The function of the first, anovulatory surge (anLH) is unknown, nor is it clear what regulates the timing of these two surges. To further study this observation in the Asian elephant, serum concentrations of LH, FSH, progesterone, inhibin, estradiol, and prolactin were quantified throughout the estrous cycle to establish temporal hormonal relationships. To examine long-term dynamics of hormone secretion, analyses were conducted in weekly blood samples collected from 3 Asian elephants for up to 3 yr. To determine whether differences existed in secretory patterns between the anLH and ovLH surges, daily blood samples were analyzed from 21 nonluteal-phase periods from 7 Asian elephants. During the nonluteal phase, serum LH was elevated for 1-2 days during anLH and ovLH surges with no differences in peak concentration between the two surges. The anLH surge occurred 19.9+/-1.2 days after the end of the luteal phase and was followed by the ovLH surge 20.8+/-0.5 days later. Serum FSH concentrations were highest at the beginning of the nonluteal phase and gradually declined to nadir concentrations within 4 days of the ovLH surge. FSH remained low until after the ovLH surge and then increased during the luteal phase. Serum inhibin concentrations were negatively correlated with FSH during the nonluteal phase (r = -0.53). Concentrations of estradiol and prolactin fluctuated throughout the estrous cycle with no discernible patterns evident. In sum, there were no clear differences in associated hormone secretory patterns between the anLH and ovLH surge. However, elevated FSH at the beginning of the nonluteal phase may be important for follicle recruitment, with the first anLH surge acting to complete the follicle selection process before ovulation.

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Hormone secretion in the asian elephant (Elephas maximus): characterization of ovulatory and anovulatory luteinizing hormone surges.

Serum samples were obtained either weekly or daily from six mature elephant cows for periods of 7 to 30 months from April 1979 to November 1981, to rigorously describe the hormonal and behavioral components of the reproductive cycle in the Asian elephant. The estrous state of each elephant was concurrently monitored through quantification of the frequency of male urine testing behavior (Flehmen-like response) under controlled conditions. Concentrations of progesterone (P4) and cstradiol (E2) were determined in 1.0 ml of serum by radioimmunoassay (RIA) after diethylether extraction and purification on Sephadex LH-20 columns. The presence of gonadotropic activity was assessed with a rat luteinizing hormone (LH) RIA and by an in vitro mouse Leydig cell bioassay. Fifteen ovarian cycles averaging 16.3 ± 0.4 (mean ± SEM) weeks in length were observed in six females. The luteal phase was 10.5 ± 0.3 weeks, and 5.1 ± 0.4 weeks separated subsequent luteal periods. Estradiol concentrations were extremely variable, and no distinct preovulatory E2 surge was associated with the onset of P4 secretion. However, the onset of P4 release occurred during a single 24-h period and reached maximum levels within 2 to 3 weeks. Peaks of immunoreactive LH were observed, although more than 50% of such “surges” were unrelated to increments in P4 secretion, and no evidence of bioactivity was observed in any serum sample. Pregnancy was indicated by continued secretion of P4 after the 12-week luteal phase, and elevated levels (400 to 1200 pg/mI) were seen throughout the first year and during the last 6 months of gestation. Serum concentrations of P4 fell dramatically before parturition, consistent with a role for this steroid in the regulation of gestational length. Male urine testing behavior was clearly cyclical, and maximal interest during the late interluteal period was followed by a rapid decrease with the onset of P4 secretion. These data provide the first substantive description of the hormonal milieu of the reproductive cycle, concurrent male behavior, and the serum hormonal patterns at the onset and termination of gestation in this endangered species.

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Watson Pf

Papers

Detection of oestrus in the African elephant (Loxodonta africana)