Assistant Professor Vanderbilt University Nashville, United States
Background/Question/Methods
Animals must obtain energy to survive, but the activity required to obtain energy is also energetically costly, so animals must balance energy intake against expenditure. Temperature increases in tropical ecosystems due to climate change may affect animals’ activity patterns, and energetic balance. Estimating energy expenditure involves estimating day range, but common methods for doing so have been shown to yield underestimates. We aim to evaluate energy balance and estimate a realistic day range for white-lipped peccaries (Tayassu pecari), based on spatially-explicit data on foraging bouts. We implemented a probabilistic method to estimate energy-intake per distance travelled. Our objective was to determine a range of energetic intakes and expenditures for white-lipped peccaries. Our data comes from the Atlantic Forest biome, in the state of São Paulo, Brazil. In summer of 2019 we followed foraging trails and recorded the frequency of feeding bouts along those trails. We performed a Monte Carlo analysis to estimate the distribution of feeding bouts per distance traveled. We used a well-established allometric equation to estimate energy expenditure during travel, which we combined with our estimates of energy intake from the Monte Carlo analysis to predict the minimum distance sub-herds of varying size must travel daily.
Results/Conclusions
Based on our foraging trail data, the distances which white-lipped peccaries travelled between feeding bouts were fit to a mixed distribution with an exponential head and a generalized pareto tail. A Monte Carlo analysis drawing on this distribution we estimated that the number of feeding bouts over 1 km of travel varies between 0 and 28, with a mean of 18.18 feeding bouts per 1 km. For populations eating primarily Euterpe edulis palm fruits, we estimate this results in a foraging group consuming between 0 and 1,0060 fruits per 1 km, with a mean of 665.2 fruits consumed per km. By plotting average calories consumed per distance travelled against a mass-based estimate of calories expended per distance travelled we estimated that for groups ranging from 12 to 60 individuals, minimum day range ranges from 1.92 to 8.03 km per day. Our findings support previous assertions that estimates of day range based on GPS-collars or telemetry data are likely to be underestimates for highly mobile species such as white-lipped peccaries. Incorporating fine-scale spatially explicit data on feeding bouts into estimates of energy intake and expenditure as we do here provides a robust alternative.
