Biomarkers including reproductive hormones and indicators of energy balance can be used to analyze health status and physiology in wild animals. Non-invasive collection of urine or feces enables biomarker monitoring, important for critically endangered species like orangutans. Hormonal measurements must control for urine concentration, typically done using creatinine or specific gravity. Specific gravity measurement compares the density of urine with the density of water. Creatinine is a breakdown product of muscle metabolism that is excreted from the body at a relatively stable rate, and it is an indicator of relative muscle mass in many species. Here, we measure specific gravity in urine samples from captive female orangutans using a digital hand-held urine specific gravity refractometer. We compare specific gravity to previously measured creatinine values and assess the influence of time of collection and refractometer temperature on specific gravity. We found a significant positive correlation between specific gravity and creatinine concentrations (N=1021, Pearson’s R=0.578, p<0.001). While we found no significant correlation between the time that samples were collected and specific gravity readings (N= 314, Pearson’s R=0.079, p=0.17), readings from morning samples were slightly but significantly lower (N=255, mean=1.008) than afternoon samples (N=60, mean=1.009) (independent samples t-test, t312=-1.969, p=0.05). We found a significant negative correlation between specific gravity and refractometer temperature (Pearson’s R=-0.23, p<0.001), highlighting the need to control for urine temperature when using thawed samples.
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Noninvasively Monitoring Orangutan Health Status: Determining Urine Concentrations
Biomarkers including reproductive hormones and indicators of energy balance can be used to analyze health status in wild animals. Non-invasive measures, analyzed through urine or feces, enable biomarker monitoring without interfering with organisms, important for critically endangered species like orangutans. A measure of urine concentration such as creatinine concentrations or specific gravity is necessary when analyzing urine samples. Here, we measure specific gravity in urine samples from three captive female orangutans using a digital hand-held urine specific gravity refractometer. We compare specific gravity to previously measured creatinine values for two orangutans, and assess the influence of time of collection and refractometer temperature on specific gravity for all three. We found a significant positive correlation between specific gravity and creatinine concentrations (N=1021, Pearson’s R=0.578, p<0.001). While we found no significant correlation between the time that samples were collected and specific gravity readings (N= 314, Pearson’s R = 0.079, p=0.17), readings from samples collected in the morning were slightly but significantly lower (N=255, mean=1.008) than samples collected in the afternoon (N=60, mean=1.009) (independent samples t-test, t312=-1.969, p=0.05). We found a significant negative correlation between specific gravity and the refractometer temperature (Pearson’s R=-0.23, p<0.001). In future studies, specific gravity can be used to determine urine concentration rather than creatinine, which is more costly and requires more time for lab work. Our future research will examine the correlation between specific gravity and creatinine concentrations as orangutans age, and the effects of aging on muscle wasting and reproductive status.
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- NSF-PAR ID:
- 10188140
- Date Published:
- Journal Name:
- Fifth Annual Meeting of the Northeastern Evolutionary Primatologists
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Orangutan habitats are characterized by fluctuations in the availability of ripe fruits. During non-fruiting periods orangutans typically incorporate more lower-quality foods such as pith and bark in their diet. Condensed tannins (CT) are secondary plant compounds that bind to proteins, thus impeding the digestibility of proteins, and tending to make foods bitter or unpalatable. We analyzed condensed tannin content in 129 plant samples collected from Gunung Palung National Park in Borneo, Indonesia between 1994 and 2001. We predicted that CT concentrations would be highest in bark, and that there would be a correlation between protein and condensed tannin content. We used ANOVA with Bonferonni’s method for post-hoc comparisons to test for differences in 11tannin content between plant parts, and Pearson’s correlation to test for relationships between tannin concentrations and other nutrients. There were significant differences in condensed tannin content (F(¬4)=2.70, p=0.03) but no differences after adjusting the alpha-level for post-hoc comparisons. Whole fruit (including the skin) tended to have the highest CT concentration. However, we found no correlation between CT and concentration of nutrients including crude protein (R=0.12, p=0.19, N=127), free simple sugars (R=-0.09, p=0.40, N=100), or fiber (R=-0.38, p=0.67, N=128). This underscores that plants rich in desirable nutrients may also be rich in antifeedants, posing challenges for orangutan consumption and digestion even as they provide a source of high-quality energy. Additionally, for some food categories where high tannin content is predicted, such as bark, orangutans may be choosing to eat species that are lower in these compounds. Funders: Boston University Undergraduate Research Opportunities Program, NSF (BCS-1638823, BCS-0936199); National Geographic; USFish/Wildlife (F18AP00898, F15AP00812, F13AP00920, 96200-0-G249, 96200-9-G110, 9414388); Leakey; Disney Wildlife Conservation; Wenner-Gren; Nacey-Maggioncalda; Orangutan Conservancy; Conservation, Food, and Health Foundation.more » « less
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Methods This study collected spot urine samples and corresponding weather data along with data on household water and food insecurity, demographics, and health characteristics among 266 Tsimane' households (N = 224 men, 235 women, 219 children) and 136 Daasanach households (N = 107 men, 120 women, 102 children).
Results The prevalence of hypohydration among Tsimane' men (50.0%) and women (54.0%) was substantially higher (
P < .001) than for Daasanach men (15.9%) and women (17.5%); the prevalence of hypohydration among Tsimane' (37.0%) and Daasanach (31.4%) children was not significantly different (P = .33). Multiple logistic regression models suggested positive but not statistically significant trends between household water insecurity and odds of hypohydration within populations, yet some significant joint effects of water and food insecurity were observed. Heat index (2°C) was associated with a 23% (95% confidence interval [CI]: 1.09‐1.40,P = .001), 34% (95% CI: 1.18‐1.53,P < .0005), and 23% (95% CI: 1.04‐1.44,P = .01) higher odds of hypohydration among Tsimane' men, women, and children, respectively, and a 48% (95% CI: 1.02‐2.15,P = .04) increase in the odds among Daasanach women. Lactation status was also associated with hypohydration among Tsimane' women (odds ratio = 3.35, 95% CI: 1.62‐6.95,P = .001).Conclusion These results suggest that heat stress and reproductive status may have a greater impact on hydration status than water insecurity across diverse ecological contexts.
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