Animal Sciences


Specific gravity is a urinalysis parameter that measures the concentration of excreted molecules in urine. Clinically, specific gravity measures the kidney’s ability to dilute or concentrate urine and reflects the concentration of urine during renal filtration. We explored species differences in the specific gravity of various primates’ urine samples, including Alouatta palliata, Alouatta caraya, Callithrix jacchus, Sapajus apella, and Saimiri sciureus. A refractometer was used to measure the urine samples. The urine samples obtained from the wild howler monkeys, Alouatta palliata, had a higher specific gravity than the other primate species’ samples, which were all obtained from captive animals and did not have differing values. These results held true even when controlling for individual differences between animals. Our results indicate that open access to water while in captivity affects specific gravity more than species differences in renal physiology, however specific gravity is a general parameter and might not detect other possible differences in renal physiology that exist between nonhuman primate species.