Notes on the activity patterns of 12 species of southern African rodents and a new design of activity monitor

Abstract

The circadian activity patterns of 12 species of southern African rodents are described under controlled laboratory conditions. Activity was measured in a newly described apparatus, in which rodents, traversing infra-red light beams placed across several arenas and nest-boxes, activated a microprocessor which quantified, and regularly printed data on a recorder. Diel patterns of activity were present in all species and most species were nocturnal. Locomotion, and other behaviours, were continuous or discontinuous (phasic) during activity periods. Short-term periods of activity were most obvious in species with a low body mass and were thought to be associated with a feeding rhythm. Continual diel activity with a regular short-term rhythm characterized Otomys irroratus, paralleled that of the microtines, and is believed to be necessitated by specific adaptations to herbivory. Crepuscularity in Rhabdomys pumilio may be associated with Hodotermes prédation, while nocturnalism In (arboreal) Graphlurus murlnus is believed to . reduce competition with diurnal granivorous and Insectivorous birds. Notes describe the seasonal change in activity of four species: such differences were less marked than those reported for temperate species.