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Measuring energy balance and energy metabolism can provide crucial information for understanding the ecological and behavioral drivers of an animal's energetic and physiological condition. Both urinary C‐peptide (uCP) of insulin and urinary total triiodothyronine (uTT3) have been validated as noninvasive biomarkers of energy balance and metabolic activity in haplorrhine primates. This study attempts to validate uCP and uTT3 measures in strepsirrhines, a phylogenetically distinct primate clade, using the ruffed lemur (genusVarecia) as a model. We experimentally manipulated the diet of captive black‐and‐white (Varecia variegata) and red (Varecia rubra) ruffed lemurs at Duke Lemur Center across a 4‐week period. We collected urine samples from subjects (n = 5) each day during 1 week of control diet, 2 weeks of calorie‐restricted diet and 1 week of refeeding, designed to temporarily reduce energy balance and metabolism. We also tested the outcome of filter paper as a storage method by comparing to controls (frozen at −20°C) to assess its suitability for studies of wild populations. We successfully measured uCP and uTT3 levels in frozen urine samples using commercial enzyme immunoassay kits and found that both biomarkers were excreted at lower concentrations (C‐peptide: 1.35 ng/mL, 54% reduction; TT3: 1.5 ng/mL, 37.5% reduction) during calorie‐restricted periods compared to normal diet periods. Filter paper recovery for uCP was 19%, though values were significantly positively correlated with frozen control samples. uTT3 could not be recovered at measurable concentrations using filter paper. These methods enable noninvasive measurement of energetic conditions in wild strepsirrhines and subsequent assessment of relationships between energy balance and numerous socioecological drivers in primate populations.

 

Identifying biomarkers of age-related changes in immune system functioning that can be measured non-invasively is a significant step in progressing research on immunosenescence and inflammaging in free-ranging and wild animal populations. In the present study, we aimed to investigate the suitability of two urinary compounds, neopterin and suPAR, as biomarkers of age-related changes in immune activation and inflammation in a free-ranging rhesus macaque ( Macaca mulatta ) population. We also investigated age-associated variation in gene transcription from blood samples to understand the underlying proximate mechanisms that drive age-related changes in urinary neopterin or suPAR. Neopterin was significantly positively correlated with age, and had a moderate within-individual repeatability, indicating it is applicable as a biomarker of age-related changes. The age-related changes in urinary neopterin are not apparently driven by an age-related increase in the primary signaler of neopterin, IFN-y, but may be driven instead by an age-related increase in both CD14+ and CD14− monocytes. suPAR was not correlated with age, and had low repeatability within-individuals, indicating that it is likely better suited to measure acute inflammation rather than chronic age-related increases in inflammation (i.e., “inflammaging”). Neopterin and suPAR had a correlation of 25%, indicating that they likely often signal different processes, which if disentangled could provide a nuanced picture of immune-system function and inflammation when measured in tandem. 

Brain structure is predicted by social network size but not other key social attributes in free-ranging monkeys.