Carbon-Nitrogen Ratios in Animal Feces (IMAGE) Duke University Caption Carbon-to-nitrogen ratios in poop vary between animals as a result of diet and physiology. These ratios also govern the abundance of microbes in their guts. Credit Aspen Reese - Harvard Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.