COS 50-5 - Using fractal analyses to characterize movement paths of white-tailed deer and response to spatial scale

Wednesday, August 5, 2009: 9:30 AM
Taos, Albuquerque Convention Center
Stephen L. Webb1, Samuel K. Riffell1, Kenneth L. Gee2 and Stephen Demarais1, (1)Wildlife and Fisheries, Mississippi State University, Mississippi State, MS, (2)Agriculture Research, The Samuel Roberts Noble Foundation, Ardmore, OK
Background/Question/Methods: Understanding movement is important to mammal biology, ecology, and management, but it is often difficult to determine spatial scale and test hypotheses about how and why animal movement responds to environmental conditions. We used fractal D as a measure of tortuosity because it described animal movement patterns and was useful for testing hypotheses about sex, home range size, monthly rainfall, and reproductive phase effects on movement paths and for detecting changes in movement patterns of animals in response to spatial scale. To test these hypotheses, we captured and fitted 33 (18 females, 15 males) white-tailed deer (Odocoileus virginianus) with global positioning system (GPS) collars. 

Results/Conclusions: Females moved more tortuously than males (t1,31 = 4.51, P < 0.001) with females having higher D estimates (1.75 ± 0.035) than males (1.549 ± 0.025). These differences in search strategy influenced home range size of females (R² = 0.256, P = 0.032) but not for males (P = 0.432). Therefore, females and males may perceive landscape structure differently. Rainfall predicted D for females (R² = 0.174, P = 0.002); thus, females may have been able to forage more intensively in a smaller area due to increased forage availability. Fractal D of females was greatest during the parturition period (1.468 ± 0.02) likely due to restricted movements to smaller areas or increased foraging. Male home range size was similar between spring and rut, but D was significantly lower during rut indicating that deer will change movement patterns within previously established home ranges. Scale-invariant patterns in movement were likely to be within foraging patches or home ranges whereas scale-variant movement patterns may be due to movements across habitat patches. Fractal analyses were useful in detecting changes in movement patterns relative to spatial scale and for testing research hypotheses.

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