Monitoring of Reproduction and Influence of Fecal Progesterone on Reproductive Cyclicity in Captive Sri Lankan Sambar Deer (Rusa Unicolor Unicolor)

Abstract

This study examines the length of the estrous cycle in 16 Sambar deer hinds in National zoological gardens in Dehiwala and Kegalle, Sri Lanka (NZGDK) assessed with the use of changes in progesterone concentrations, along with the changes in the profile of this hormone and by the visual estrus manifestations. The objectives of the present study were to characterize ovarian activity throughout the estrous cycle and the non-pregnant luteal phase of captive sambar deer in Sri Lanka. These objectives were achieved with the use of radioimmunoassay (RIA) to measure fecal concentrations of progesterone and visual estrus manifestation. Fecal samples were collected from non-pregnant sambar deer hinds (aged 2–4 years)over the period of six months on daily basis, both during breeding and non-breeding seasons. Estrous cycles were recorded in non-pregnant females, based on fecal progesterone concentrations. The average estrous cycle length was 26.1±2.08 days (mean ± SEM) and 2.10 ± 0.51 days in the inter-luteal phase.The average fecal progesterone concentrations attained the peak mid-luteal values of 2.74 ng mL–1. There appeared to be variation in fecal progesterone amplitude between animals and between dates, but the low frequency of sampling prohibited confirmation of trends. Behavioral estrus was detected only when the average progesterone concentrations were less than 0.07 ng mL–1. However, not all periods of depressed progesterone secretion were associated with the observed estrus. Behavioral estrus was detected in hinds when progesterone concentrations were less than 0.07 ng mL–1; a subsequent rise in progesterone indicated ovulation taking place at this time.

Population dynamics and social organization of sambar (Rusa unicolor unicolor) in Horton Plains National Park, Sri Lanka

“…However, behavioral, physiological, and endocrinal studies of captive sambar hinds in Sri Lanka have shown them to be aseasonal and polyestrous (Weerasekera, Subotsina, et al, 2021), in contrast to our study in the wild montane grassland setting. We cannot reconcile these contrasting findings except that the grassland ecosystem and high elevation of HPNP may constrain calf production to a shorter period and thereby set up a more synchronized mating season.…”

“…Similar to the HPNP, Karanali‐Bardia grasslands, as well as Tadoba National Park, Chandrapur, Maharashtra, India (Kunhlkannan & Rama rao, 2013), are introduced with carpet grass of Pennisetum spp. which is palatable for sambar (Dinerstein, 1979) and hence supported large herds of them (Weerasekera, Subotsina, et al, 2021) also showing a seasonality in social structures and male antler stages.…”