COS 77-3 - Modeling movement patterns and resource acquisition in spatially distinct fragmentation scenarios

Thursday, August 11, 2016: 2:10 PM
305, Ft Lauderdale Convention Center
Jennifer Leigh Bradham, Earth and Environmental Sciences, Vanderbilt University, Maria Luisa Jorge, Earth & Environmental Sciences, Vanderbilt University, Nashville, TN, Brandt Gibson, Vanderbilt University, Julia Oshima, Ecologia, UNESP, Rio Claro, Brazil, Alexine Keuroghlian, WCS-Brazil, Campo Grande, Brazil and Milton Ribeiro, Universidade Estadual Pauliasta
Background/Question/Methods

From escaping predators, to mating and locating food, animal movement is crucial to survival and plays a key role in shaping the surrounding environment. Movement patterns of highly mobile, herding species generally trace resource availability. However, increased habitat fragmentation and land-use change can result in fluctuations of spatial resource distribution and availability. Understanding underlying, intrinsic movement patterns can have predictive capabilities when evaluating the success of resource acquisition among differing fragmentation scenarios. White-lipped peccaries (Tayassu pecari) are the only Neotropical mammal to travel in large herds, and as ecosystem engineers, they exhibit unique local top-down effects in environments where they are found.  Primarily frugivores, white-lipped peccaries are restricted to densely forested habitats of Central and South America and require large swaths of covered forest to sustain populations. Alterations to peccary populations and their movement patterns may translate to unfavorable modifications of the surrounding landscape. We assessed white-lipped peccary movement patterns (step lengths and angles) from GPS-collared individuals in rural landscapes of central Brazil (Cerrado biome). Through R statistical package, movement data were fitted to a theoretical distribution, which was then evaluated for food acquisition success between two different movement scenarios.

Results/Conclusions

Using Fitdistrplus package and resulting AIC values, preliminary results from nine months of peccary location data (n=1643) reveal that step lengths are best expressed through a Weibull, gamma, or exponential distribution (AIC values of -2809.31, -2808.02, and -2809.96, respectively), while angles best fit a wrapped Cauchy distribution as compared to a circular uniform distribution. However, a random walk model choosing step lengths from a Weibull distribution and angles from a wrapped Cauchy distribution (advective movement) compared to a model with angles chosen from a circular uniform distribution (diffusive movement) suggested peccaries contact resources three times more when movement is more diffusive. Given that the movement data was recovered from an ovoid fragment, the disagreement between simulation and empirical data may indicate fragmentation setting alters optimal foraging patterns.  Distribution fitting of movement data from 11 additional GPS-collared peccaries currently being tracked in other fragmentation settings and ecosystems (e.g. Pantanal biome) will provide a better understanding of whether peccaries alter movement patterns when the landscape changes or whether herds from distinct landscapes can still be described by the same underlying theoretical distributions. Future simulation work will additionally assess whether movement reflects different optimal foraging strategies among varying spatial distributions of consumable resources.