Endocrine patterns of the estrous cycle and pregnancy of wildebeest in the Serengeti ecosystem

Abstract Despite the importance of the western white-bearded wildebeest ( Connochaetes taurinus mearnsi ) to the Serengeti–Mara ecosystem, surprisingly little is known about the reproductive physiology of this keystone species. A longitudinal, non-invasive endocrine study was conducted on female wildebeest captured from the Serengeti–Mara migration and maintained for ∼16 months in large fenced enclosures within the species’ natural range. An intact bull was introduced to a female subgroup ( n = 5), while remaining females ( n = 10) were unexposed to a male. Fecal progestagen patterns reflected ovarian activity and pregnancy. In non-pregnant animals, luteal and inter-luteal baseline progestagen values differed ( p < 0.001) over time, thereby allowing identification of recurrent estrous cycles. The average durations of the luteal phase, estrous cycle, gestation, and post-partum anestrus were 14.3 ± 0.5, 22.6 ± 1.0, 240.8 ± 11.7, and 104.1 ± 15.6 d, respectively. Annual reproductive patterns indicated a distinctive period of ovarian activity that extended from 13 May through 3 December (203.5 ± 29.9 d) with all unmated females displaying from one to 14 estrous cycles. Progestagens were higher ( p < 0.001) in pregnant ( n = 4) than non-pregnant ( n = 10) cows. These data (1) reveal the value of fecal hormone monitoring for establishing the first ever endocrine profiles of female wildebeest in semi-free-living conditions in their native range, and (2) indicate that the species is a seasonal breeder that is polyestrous and a spontaneous ovulator.