Behavioral rhythms in the Nilgiri langur,Presbytis johnii

Eighteen complete daily profiles of 16 behaviors were compiled for three troops of Nilgiri langurs from Periyar Sanctuary in South India. Daily behavioral peaks from these profiles were tested for their associations with each other. Daily rhythms of feeding and resting showed four to eight peaks per day. When all observation days were lumped, however, a bimodal curve resulted as noted by most authors who have studied activity rhythms. The major daily behavioral associations were as follows: (1) feeding occurred during high rates of movement although not during major movement periods; (2) measures of troop movement were interrelated and occurred when troop members were dispersed; (3) movement was related to such active behaviors as whooping displays, coughing, juvenile whining, urinating, and scratching; (4) the above active behaviors showed some positive associations with each other; (5) play, grooming, and scratching showed positive associations with each other; and (6) rest periods were primarily periods of close social contact when grooming occurred and juveniles were with their mothers.