Endocrine milieu of perioestrus in the giant panda (Ailuropoda melanoleuca), as determined by non-invasive hormone measures

Abstract

The aim of the present study was to determine the efficacy of faecal hormonal measures for evaluating ovarian activity in a significant sized cohort of giant pandas during the perioestrual period. Faecal excretion of oestrogen and progestagen metabolites corresponded with urinary patterns and receptive behaviours. Longitudinal assessment of 10 females revealed that, on average, faecal oestrogen concentrations started to rise (P < 0.05) above baseline (baseline mean +/- s.e.m.; 64.7 +/- 6.6 ng g(-1)) 5 days before the preovulatory oestrogen peak (484.6 +/- 126.8 ng g(-1)), which was followed by a gradual descent over 4 days to nadir. Mean faecal progestagen metabolite concentrations increased approximately twofold above baseline (from 186.2 +/- 37.7 to 347.2 +/- 75.7 ng g(-1); P < 0.05) during the 20-day interval after the preovulatory oestrogen surge. Variability within and among females precluded the use of a threshold of oestrogen or progestagen metabolites to predict reproductive status, yet faeces collected 2-3 days per week provided sufficient data to recognise that an individual was in the perioestrual period. Finally, in females that were examined for at least 3 consecutive years, there was an 18-53 day variation in the onset and an 8-13 day variation in the duration of perioestrual behaviour from year to year. In summary, these findings indicate that gonadal hormone profiles associated with the period immediately before, during and after oestrus are accurately revealed by analysis of the fibrous faeces of the giant panda. This approach has potential value for providing point-in-time information on the reproductive status of free-living individuals.