Estimation of energetic condition in wild baboons using fecal thyroid hormone determination

Abstract

Understanding how environmental and social factors affect reproduction through variation in energetic condition remains understudied in wild animals, in large part because accurately and repeatedly measuring energetic condition in the wild is a challenge. Thyroid hormones (THs), such as triiodothyronine (T3) and thyroxine (T4), have a key role in mitigating metabolic responses to energy intake and expenditure, and therefore are considered important biomarkers of an animal's energetic condition. Recent method development has shown that T3 and T4 metabolites can be measured in feces, but studies measuring THs in wild populations remain rare. Here we measured fecal T3 metabolites (mT3) in baboons, and tested whether the conditions of collection and storage used for steroid hormones could also be used for mT3; we focused on mT3 as it is the biologically active form of TH and because fecal T4 metabolites (mT4) were below detection levels in our samples. We also tested if mT3 could be determined in freeze-dried samples stored for long periods of time, and if these concentrations reflected expected biological variations across seasons and reproductive states. Our results show that mT3 can be measured with accuracy and precision in baboon feces. The conditions of collection and storage we use for steroid hormones are appropriate for mT3 determination. In addition, mT3 concentrations can be determined in samples stored at -20 °C for up to 9 years, and are not predicted by the amount of time in storage. As expected, wild female baboons have lower mT3 concentrations during the dry season. Interestingly, mT3 concentrations are lower in pregnant and lactating females, possibly reflecting an energy sparing mechanism. Retroactive determination of mT3 concentration in stored, freeze-dried feces opens the door to novel studies on the role of energetic condition on fitness in wild animals.

Factors Affecting Glucocorticoid and Thyroid Hormone Production of Island Foxes

“…Although the underlying causes of reduced thyroid function in these foxes remains unknown, exposure to environmental toxins has been suggested (Munson 2010). Average fecal T3 concentrations measured in this study were higher than those reported for maned wolves (Vynne et al 2014) and several primate species (Schaebs et al 2016, Gesquiere et al 2018). Although these studies used different immunoassays and concentrations are not directly comparable, there is no indication that overall T3 concentrations of island foxes are abnormally low.…”

Linking diet quality and energy demand in free‐living guanacos: an eco‐physiological innovative approach

“…With regard to energy status in wild mammals, future studies could incorporate new physiological mediators [i.e. faecal Thyroid Hormone metabolites (THs); Gesquiere et al ., ], which would reinforce the understanding of the Biphasic Model that we have proposed. Guanacos present interesting features to evaluate the relationships between glucocorticoids and their response to energy demanding tasks.…”

Methods for detecting Zika virus in feces: A case study in captive squirrel monkeys (Saimiri boliviensis boliviensis)

“…It is common practice for scientists studying nonhuman primates in the wild to have teams that follow the animals on a daily basis and collect samples from known individuals. These methods allow collection of fecal samples that are regularly preserved and processed for laboratory analyses for hormonal, genetic, and disease studies [32–34], and the methods can be modified to monitor ZIKV in study populations. Importantly, researchers will also now have a noninvasive way to check for ZIKV, particularly if reproductive issues are observed or if an infection is suspected.…”