Growth and Reproduction of Hispid Cotton Rats (Sigmodon hispidus) in Response to Naturally Occurring Levels of Dietary Protein

Abstract

Hispid cotton rats ( Sigmodon hispidus ) ingest both monocotyledon (monocot) and dicotyledon (dicot) plants, ostensibly to balance intake of nutrients. On the Texas coastal prairie, monocots are more abundant, require less handling time, and have more fiber and soluble carbohydrates than dicots, which contain more protein, lipid, water, energy, and minerals. Because availability of protein may be limiting here, cotton rats were raised on artificial diets that mimicked protein content of either monocots (4%) or dicots (11%). Body mass, growth rate, and length of hind foot were lower and liver mass was higher in individuals fed a monocot-protein diet. Tissue protein, but not lipid, content was higher in individuals fed a dicot-protein diet. First estrus occurred at the same body mass on both diets, but slower growth on a monocot-protein diet resulted in females being 50% older at first estrus. Cotton rats must ingest dicots to obtain sufficient protein for growth and reproduction because monocots are not a complete food source.