Ultrasound and endocrine evaluation of the ovarian cycle and early pregnancy in the Sumatran rhinoceros, Dicerorhinus sumatrensis

Abstract

Longitudinal ultrasound and endocrine evaluations were conducted in two adult female Sumatran rhinoceroses (Dicerorhinus sumatrensis) over a period of 12-22 months to learn more about their reproductive physiology. Rectal ultrasonography was conducted to monitor ovarian activity. Blood samples were collected and analysed for progesterone and LH, and faecal samples were analysed for progestin metabolites. One female showed cyclic ovarian activity during the study period, whereas the other female showed no evidence of ovarian activity. The cyclic Sumatran rhinoceros appeared to be an induced ovulator, the first of its kind reported within the Perrisodactyla. Ultrasound examinations of the ovaries revealed the formation of anovulatory haemorrhagic follicles when the animal was not mated. These follicles appeared to undergo varied degrees of luteinization that resulted in irregular faecal progestin profiles. When allowed to mate, the female showed a 21 day reproductive cycle that was reflected in both faecal progestin and serum progesterone profiles. The concentration of serum LH was baseline before mating, increased approximately 30-fold within 1-2 h of intromission and returned to baseline within 22 h. Ovulation occurred within 46 h of copulation. The female conceived three times during the study. Pregnancy was detected using ultrasonography 14-16 days after mating, and the concentration of both serum progesterone and faecal progestins remained high. Early embryogenesis appeared to be similar to that in horses. However, each pregnancy terminated unexpectedly within the first 3 months of gestation. This study demonstrates the important role that basic research and reproductive technology can play in developing a natural breeding programme for an endangered animal in captivity.

Follicular, endocrine and behavioural dynamics of the Indian rhinoceros (Rhinoceros unicornis) oestrous cycle

“…First, changes in oestrogen concentrations are readily measured in the urine and/or faeces and reflect cyclical patterns, whereas in the Sumatran, African black and African white rhinoceros oestrogen metabolite analyses have not proven reliable as a means of monitoring ovarian function (Ramsay et al 1987, Hodges & Hindle 1988, Roth et al 2001. Futhermore, studies characterizing the reproductive cycle through the measurement of excreted steroid hormone concentrations and animal behaviour revealed wide intra-and inter-animal variations in the oestrous cycle length of this species (Kassam & Lasley 1981, Kasman et al 1986, Schwarzenberger et al 2000.…”

“…In order to guarantee maximal genetic variation in subsequent generations of captive Indian rhinoceroses, breeding and successful reproduction must occur with regularity between specifically paired males and females. Natural breeding attempts among captive Asian rhinoceros species frequently result in severe aggression between males and females (Khan et al 1999, Roth & Brown 1999, Roth et al 2001. Unlike the Sumatran rhinoceros (Dicerorhinus sumatrensis), the Indian rhinoceros typically exhibits overt signs of oestrous behaviour that traditionally have been used to time introductions for mating.…”

“…Therefore, the timing of breeding or AI relies heavily on an understanding of female reproductive physiology, yet reproductive data on most exotic animals are still very limited. However, recent advances in understanding female reproductive physiology in the Sumatran, African black (Diceros bicornis) and African white (Ceratotherium simum) rhinoceroses have expanded the knowledge base while revealing substantial variation in reproductive function among the rhinoceros species (Schwarzenberger et al 1993, Berkeley et al 1997, Radcliffe 1997, 2001, Roth et al 2001, 2004, Patton et al 1999, Roth & Brown 1999. Several of these studies utilized a combination of sera, faecal and/or urinary hormone analysis and rectal ultrasonography to delineate oestrous cycle dynamics, thereby producing information directly applicable to captive breeding efforts.…”

“…Several of these studies utilized a combination of sera, faecal and/or urinary hormone analysis and rectal ultrasonography to delineate oestrous cycle dynamics, thereby producing information directly applicable to captive breeding efforts. For example, longitudinal analysis of serum progesterone concentrations and ultrasound imaging of ovarian and uterine tissue led to our understanding of Sumatran rhinoceros reproductive physiology and resulted in the first successful breeding of a captive Sumatran rhinoceros in 112 years (Roth et al 2001(Roth et al , 2004. Similar information regarding the reproductive biology of the Indian rhinoceros is limited.…”

“…Therefore, detailed data on follicular dynamics, growth and ovulation do not exist. It was primarily through ultrasound monitoring that another Asiatic species, the Sumatran rhinoceros, was discovered to be an induced ovulator that exhibits a 21-day reproductive cycle when allowed to mate (Roth et al 2001). In contrast, spontaneous ovulation has been documented by ultrasonography in both African black and African white rhinoceroses, with mean cycle lengths of 26 and 33 days respectively (Radcliffe et al 1997(Radcliffe et al , 2001).…”