Monitoring of reproductive endocrinology is a very important tool in the management of animal populations both in captivity and in the wild. Whenever possible measuring key indicators such as estrogens, progestogens, and androgens using non-invasive sample types is prefered so that animals under study are not subjected to the stress of handling and blood collection.
It has become quite common to measure reproductive status in mammals using urine or fecal samples, which can typically be easily collected. In 2016 Sterling et al. from Washington University in St. Louis and the St. Louis Zoo reported that fecal samples can also provide for reliable tracking of reproductive hormones in birds.
The team from St. Louis tracked Estrogen, Progesterone, and Testosterone in fecal samples collected weekly from 13 individual blue-throated piping guans over the course of more than 2 years. All samples were extracted by heating to 37°C overnight in PBS in the presence of B-glucuronidase followed by the addition of methanol and shaking for a minimum of 16 hours. The liquid extracts were then collected, centrifuged, and stored at -80°C until assay. The remaining solids were dried and weighed for normalization. Extracts were assayed using Arbor Assays DetectX kits for Estradiol (K030-H), Progesterone (K025-H), and Testosterone (K032-H).
Testosterone in the samples from male birds cycled annually, being consistently highest in July and lowest in December. In the female birds, Estradiol and Progesterone both remained at baseline until just before egg laying. Estradiol increased first, approximately 17 days before egg laying, and returned to baseline on the day of egg laying. Progesterone rose approximately 11 days before egg laying and returned to baseline about 2 days after.
These data indicate that monitoring estrogen and progesterone levels in female guans can be used to reliably predict and monitor egg laying. While the blue throated guans in this study are not endangered, they are threatened by wild habitat loss. An understanding of the breeding patterns within populations could be extremely helpful monitoring wild birds. Additionally, the information gained in this study could be extremely valuable in monitoring the closely related horned guan and Trindad piping guan species which are critically endangered.