Non-invasive hormonal characterization of the ovarian cycle, pregnancy, and seasonal anestrus of the female addra gazelle (Nanger dama ruficollis)

• Female addra gazelle exhibit a previously unreported seasonal anestrus.
• Fecal steroid metabolites provide a reliable method for monitoring ovarian function in the addra gazelle.
• Estrous cycle length is comparable to the mohor sub-species.
• Peaks in U.S. births coincide with maximal rainfall in their native habitat.

Non-invasive fecal hormone metabolite monitoring was used to characterize the estrous cycle, pregnancy, and seasonal anestrus of the critically endangered addra gazelle (Nanger dama ruficollis). With less than 250 animals remaining in the wild and ∼168 individuals managed in captivity, it is crucial to maintain sustainable populations. Progestogen and estrogen profiles were obtained from analysis of fecal samples collected approximately every other day, within varying intervals, over the course of 7 years (n = 8 adult females). Average estrous cycle length was 19.5 ± 0.4 days (range, 14–26 days), with a luteal phase length of 14.6 ± 1.2 days (range, 10–16 days), and an inter-luteal period of 5.2 ± 1.4 days (range, 2–7 days). Mean gestation length for six pregnancies was 200.7 ± 0.4 days (range, 200–202 days). Fecal progestogens increased at 12 weeks of gestation and remained elevated until parturition. Addra gazelle females exhibited a period of seasonal anestrus with consistently low progestogen concentrations and no cyclic activity from about September to March. Analysis of reproductive and climate records demonstrated a peak in U.S. births that coincided with maximal rainfall in the native habitat of the addra gazelle. Results show that estrous cycle, luteal phase, and inter-luteal phase lengths in addra are similar to those observed in other gazelle species, however, to our knowledge, this is the first study to demonstrate seasonal anestrus in the Nanger genus.