Non-invasive assessment of hormonal fluctuations during pregnancy in guanacos ( Lama guanicoe ) and its application in a wild population

Abstract

Obtaining endocrinological profiles using non-invasive methodologies by the measurement of hormone fecal metabolites is awidely used method to monitor ovarian activity and pregnancy in wild species. These tools allow the obtention of physiologicalinformation without causing capture-related stress on the individuals. In this research, we aimed to 1) biologically validate anon-invasive method to assess fecal progestagens and estrogens fluctuations during gestation in guanacos (Lama guanicoe)and 2) apply this technique to assess pregnancy in a wild free-ranging population. Fecal samples were collected through thegestation period (∼12 months) of female guanacos in a 6.5-ha paddock. An increase in fecal metabolites of both hormoneswas detected. Progestagens increased gradually, in contrast to estrogens, which remained at basal values for most of thegestation period and peaked only a few days before calving. To assess pregnancy in wild free-ranging animals, fecal sampleswere collected from a population of La Payunia provincial reserve (Mendoza, Argentina) during the beginning of gestation andat the end of gestation. Through the first months of possible gestation, pregnant females represented between 40 and 80% ofthe population; at the end of gestation, only 20–40% of the females had confirmed pregnancies. Our results demonstrated thatthe polyclonal antisera and sexual hormone metabolite assays used here detect variations in the metabolites excreted throughfeces in guanacos and provide the possibility of non-invasive hormone monitoring of female reproductive status. Also, thefindings in wild conditions suggest that natural abortions could have occurred during the first months of gestation. Althoughsome abortions may be natural, the harsh environmental conditions that challenge the support of such a long gestationalprocess may be another relevant factor to consider. The results obtained here enhance our understanding of the reproductivephysiology of one of the most emblematic ungulates in South America.