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Abstract 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. 

Black-and-white ruffed lemurs (Varecia variegata) are often described as highly sensitive to habitat disturbance (White et al., 1995; Balko, 1998; Ratsimbazafy, 2002; Ratsimbazafy, 2006; Herrera et al., 2011). In fact, local habitat quality has been shown to be a major predictor of Varecia occupancy across the species’ range (Morelli et al., 2020). In Ranomafana National Park, Varecia occupy several structurally and compositionally distinct sites. Disturbed sites—those previously subject to logging—have lower densities of shorter trees with smaller canopies and lower cover, as well as lower floristic diversity than undisturbed sites (Balko, 1998; Mancini, 2023). Resultantly, sites of lower quality habitat, particularly those with fewer large fruiting trees available, have lower population numbers of Varecia, with highly disturbed sites completely absent of this taxon (e.g., Herrera et al., 2011). However, our recent observations of Varecia in a disturbed forest site in Ranomafana National Park suggests the latter is not always the case.