Protein Deprivation in Primates: III. Cage Activities and Chain-Pulling Behavior of Adult Rhesus Monkeys Maintained on Low-Protein Diets

Abstract
Three groups of adult female rhesus monkeys, maintained on low-protein diets (.5-gm, 1-gm, and 2-gm protein per kg body weight) were compared with a control group (4-gm protein per kg body weight) on a number of spontaneous cage activities and chain-pulling behavior. Although the deprived animals lost body weight and muscle tissue and they became deficient in essential amino acids and plasma albumin, they maintained their normal posture and continued to move about, vocalize, eat, drink, etc., as such monkeys usually do in their home cages. However, several specific behavioral deficiencies were revealed: reduced face and head movements, fewer eye contacts, and less chain pulling. It was concluded that the level of protein deprivation induced in this study depletes the animals' energy resources and produces a lowered anxiety threshold, so that certain additional behavioral demands cannot be supported even though routine cage activities are not impaired.