Non-Invasive Reproductive Hormone Monitoring in the Endangered Pygmy Hog (Porcula salvania)

Simple Summary

The pygmy hog is one of the world’s rarest suids and classified as an endangered species. Efforts are being made to breed them in captivity and reintroduce them into the wild. In this study, we examined reproductive hormones in captive pygmy hogs using a non-invasive method by collecting 785 fecal samples from five females and two males for 12 months. High-pressure liquid chromatography was performed to examine the presence of immunoreactive progesterone and testosterone metabolites in the fecal samples. We standardized and validated enzyme immunoassays (EIA) for fecal progesterone and testosterone metabolites. Using progesterone EIA, we were able to detect pregnancies in four females and estimate the relevant gestation period. We also recorded 172 births from the captive breeding center and found strong seasonality patterns in births. In males, fecal testosterone metabolite concentrations were higher in the breeding season than in the non-breeding season as evidenced by elevated testosterone concentrations during breeding season. A significant difference in fecal progesterone metabolites concentration was observed between non-pregnant and pregnant females. This study can directly help in monitoring the reproductive status of reintroduced hogs both in the wild and in conservation breeding programs in India and elsewhere.

Abstract

The pygmy hog (Porcula salvania), until recently was classified as a critically endangered suid facing the threat of extinction due to habitat degradation. Efforts are being made to protect the pygmy hog from extinction and breed them in captivity under the Pygmy Hog Conservation Programme (PHCP). However, very little information is available on the reproductive physiology of pygmy hogs. Therefore, the present study aims to standardize enzyme immunoassays (EIAs) for monitoring pregnancy and reproductive status using progesterone and testosterone metabolites. A total of 785 fecal samples were collected from five females and two males over a period of one year from the PHCP Research and Breeding Centre, Guwahati, Assam. High-pressure liquid chromatography (HPLC) analysis revealed the presence of immunoreactive progesterone and testosterone metabolites in feces. Mating was observed in all five females, and four of them gave birth successfully. We were able to detect pregnancy using fecal progesterone metabolites. The mean gestation period, based on mating and parturition, was estimated to be 153.25 days from the four females studied. The breeding center recorded 172 births between 1996 and 2000 and found strong seasonal patterns in the birth rate, with most of the births occurring between May and June. In the males, fecal testosterone metabolites were significantly higher in the breeding season than in the non-breeding season. This is the first study on the subject and will help with future breeding programs in other captive breeding centers and with reproductive monitoring of reintroduced populations.

Irregular ovarian activity, body condition and behavioural differences are associated with reproductive success in female eastern black rhinoceros (Diceros bicornis michaeli)

Ex situ populations of endangered species such as the black rhinoceros play an important role in global conservation strategies. However, the European captive population of eastern black rhinoceros is performing sub-optimally, with growth rates and genetic viability limited by low birth rates and high reproductive skew. We investigated several intrinsic differences between parous and nulliparous females that may underlie differences in reproductive success, including ovarian cyclicity, adrenal activity, behaviour and body condition. Faecal samples were collected from 39 females (17 parous, 15 nulliparous and 7 pre-reproductive) at 11 zoological institutions, every other day for between 4months and 6years. Progestagen metabolite concentration indicated that although all non-pregnant females exhibited ovarian activity, irregular cyclicity was common. Longer cycles (>40days) were more common in nulliparous females and periods of acyclicity observed more often in females that had not bred for at least 7years. Even when endocrine data indicated clear ovarian activity, overt behavioural signs of oestrus were not always apparent, particularly among nulliparous females. Faecal glucocorticoids did not differ between parous and nulliparous females, although did differ according to individual temperament. More unpredictable temperaments were associated with higher glucocorticoids, and nulliparous females tended to be rated as more unpredictable. Finally, nulliparous females had higher body condition scores than parous females. This is the first comprehensive survey of the reproductive physiology of this European captive population, and highlights a number of intrinsic differences related to parity, which may underlie differences in reproductive success among captive female black rhinoceros.

A practical field extraction method for non-invasive monitoring of hormone activity in the black rhinoceros

Non-invasive hormone analysis is a vital tool in assessing an animal's adrenal and reproductive status, which can be beneficial to in situ and ex situ conservation. However, it can be difficult to employ these techniques when monitoring in situ populations away from controlled laboratory conditions, when electricity is not readily available. A practical method for processing faecal samples in the field, which enables samples to be extracted soon after defaecation and stored in field conditions for prolonged periods prior to hormone analysis, is therefore warranted. This study describes the development of an optimal field extraction method, which includes hand-shaking faecal material in 90% methanol, before loading this extract in a 40% solvent onto HyperSep™ C8 solid-phase extraction cartridges, stored at ambient temperatures. This method was successfully validated for measurement of adrenal and reproductive hormone metabolites in faeces of male and female black rhinoceros (Diceros bicornis) and was rigorously tested in controlled laboratory and simulated field conditions. All the hormones tested demonstrated between 83 and 94% and between 42 and 89% recovery of synthetic and endogenous hormone metabolites, respectively, with high precision of replication. Furthermore, results obtained following the developed optimal field extraction method were highly correlated with the control laboratory method. Cartridges can be stored at ambient (cool, dry or warm, humid) conditions for periods of up to 6 months without degradation, before re-extraction of hormone metabolites for analysis by enzyme immunoassay. The described method has great potential to be applied to monitor faecal reproductive and adrenal hormone metabolites in a wide variety of species and allows samples to be stored in the field for up to 6 months prior to analysis. This provides the opportunity to investigate hormone relationships within in situ populations, where equipment and facilities may previously have been limiting.

Impacts of environmental pressures on the reproductive physiology of subpopulations of black rhinoceros (Diceros bicornis bicornis) in Addo Elephant National Park, South Africa

Black rhinoceros are an icon for international conservation, yet little is known about their physiology due to their secretive nature. To overcome these challenges, non-invasive methods were used to monitor rhinoceros in two sections of Addo Elephant National Park, South Africa, namely Addo and Nyathi. These sections were separated by a public road, and the numbers of elephants, predators and tourists were higher in Addo. Faecal samples (n = 231) were collected (from July 2007 to November 2010) from known individuals and analysed for progestagen and androgen metabolite (FPM and FAM, respectively) concentrations. As biotic factors could impact reproduction, we predicted that demographics, FPM and FAM would vary between sections and with respect to season (calendar and wet/dry), climate and age of the rhinoceros. Mean FPM concentrations from pregnant females were seven times higher (P < 0.05) than samples from non-pregnant rhinoceros. Positive relationships were found between monthly temperatures and FPM from non-pregnant females (r (2) = 0.25, P = 0.03) and the percentage of calves born (r = 0.609, P = 0.04). Although FAM peaked in the spring, when the majority of calves (40%) were conceived, no seasonal patterns in male androgen concentrations were found with respect to month of conception and parturition. Females in Addo had a longer inter-calving interval and were less likely to be pregnant (P < 0.05) compared with those in Nyathi. The biotic stressors (e.g. predators and more competitors) within Addo section could be affecting the reproductive physiology of the rhinoceros negatively. Enhanced knowledge about how black rhinoceros populations respond to environmental stressors could guide management strategies for improving reproduction.