Abstract:Body size in animals is an important trait affecting species niche differentiation and restricting similarity. Using camera-trap data over 2008–2010, we used photo-captures from 50 cameras spread throughout Mudumalai Tiger Reserve (Western Ghats, India) to assess the activity budgets of 21 mammal species ranging in body size from 1 kg to 2088 kg. Large carnivores were mostly cathemeral whereas small cat and civet species were purely nocturnal. Mongoose species were mainly diurnal possibly due to their terrestrial feeding habits and reduce competition with other sympatric small carnivores. All large and small-bodied herbivores were cathemeral and nocturnal respectively, whereas medium-sized herbivores were active during the day. Overall, small mammals tended to be mostly nocturnal, whereas large mammals were cathemeral mainly due to energy requirements and other ecological constraints. Body size showed significant negative relationship with mean vector length (clustering of activity in time) thus implying that the daily amount of time being active increased with body size. The shorter activity time (12 h) in small mammals resulted in higher mean vector length probably to utilize the available time to fulfil energy needs. The observed cathemeral activity in large mammals may be associated with travel over larger areas to acquire large quantities of food therefore they are active for a longer duration. Our results clearly support the allometric relationship between body size and activity budgets in mammals and its association with niche differentiation.
Niche differentiation among small mammals of the Alexander Archipelago in southeastern Alaska
