Space Use Patterns of the Indian Giant Squirrel (Ratufa indica centralis Erxleben) in Relation to Food Availability in Bori Wildlife Sanctuary, M.P. India

Abstract

The spatio-temporal heterogeneity of food supply and the consequent effects on food resource use and space-use patterns of the Indian giant squirrel (Ratufa indica centralis) in Bori Wildlife Sanctuary, was the focus of study. Territoriality, which may affect space-use patterns of individuals was of special interest. Climatic factors which may influence activity budgets and consequently the variability in seasonal space-use patterns are also discussed. Based on individual variation in physical characteristics, Z identified three focal animals (one male, one female and a subadult male) in the disturbed habitat (Bhainsa nala ) , and a male and female in the undisturbed habitat (Churnagundi nala) for whom dana could only be gathered in winter. Therefore seasonal changes in space-use patterns is discussed for focal squirrels in the disturbed habitat. I kept a continuous record of behaviours during focal animal sampling. Home areas were calculated based on hourly locations taken from focal data. I gridded the area used by focal squirrels and recorded the vegetation parameters. The seasonal change in resource availability was monitored by phonological observations on all trees in the grids twice a month. Squirrels in Bhainsa nala selectively utilised certain individuals of flowering and fruiting crees which was related to crop size. Squirrels included bark and leaves in their diet even when fruit resources were available. The resource use by squirrels in Churnagundi nala showed a marked difference from squirrels in Bhainsa nala in winter which was due to the poor availability of food. Individual squirrels in Bhainsa nala showed variation in food species, food items used and the percent time spent feeding on each food item indicating that resource availability was not the same for all squirrels. No significant correlation was found between resource abundance and percent use of the item. Squirrels had overlapping ranges but were otherwise solitary. Many preferred resources were rare in the habitat, and the spatio-temporal heterogeneity in food resources resulted in overlap between individuals at locally abundant food resources. Because of this heterogeneity, the defence of an exclusive area guaranteed of resources throughout the seasons is not possible. Therefore squirrel ranges overlapped, but encounters were avoided by spatial time sharing but when encounters occurred, overt aggression was seen. But at certain locally abundant resources which were located at the periphery of the home areas, squirrels tolerated each other by maintaining inter-individual distances (5-10m). The tolerance of conspecifics at these resources could also be related to the existence of dominance hierarchies which result in decreased over aggression. The intensity of use (time spent) decreased as the distance from nest increased for all squirrels. Squirrels made forays in search of food and in many cases foraging was in the peripheral areas of the range. The male’s range showed overlap with the female’s in winter which could be related to sexual activity. Squirrels had a bimodal activity pattern in both seasons but bimodality was less pronounced in the winter since activity was distributed throughout the day when temperatures were more equable Shift in onset and cessation of activity was observed with changing daylength. Time spent feeding in April was much less than in other months. Time budgets showed that in all months a higher proportion of time is spent resting which could be due to heat or cold stress in or time needed to digest food items eaten. in Activity pattern of the squirrels in winter in Churnagundir nala were influenced by the low resource availability which resulted in long basking and resting periods and negligible time spent in feeding. Though occasional forays of short duration were made, no food was located by these forays. Thus squirrels adopted a strategy of conserving energy by minimizing their requirements by resting.