Seasonal changes in gut size of the wild prairie vole (Microtus ochrogaster)

Abstract

The gut sizes of wild adult male prairie voles (Microtus ochrogaster) were found to fluctuate throughout the year. This fluctuation was highly variable, but the changes were mainly increases in the mass of the cecum and small intestine during the fall and early winter. The gut sizes (length and dry mass) of field animals were found to be similar to those of laboratory voles fed a high-fiber diet (> 40% cell wall) and (or) held at a low temperature (5 °C). In almost all cases, the gut sizes of wild voles were greater than those of laboratory voles maintained at 23 °C and fed low-fiber diets (< 20% cell wall). Despite considerable seasonal variation in gut size, there does not appear to be a strongly repeatable relationship between time of year and changes in gut size. However, because wild voles appear to have larger guts than laboratory voles acclimated to relatively energy-demanding conditions, I suggest that wild voles are living under a greater energy demand and (or) eating lower quality diets than was previously suggested.