Population consequences of movement decisions in a patchy landscape


R. E. Russell, R. K. Swihart, Dept of Forestry and Natural Resources, Purdue Univ., W. Lafayette, IN 47907, USA (robinr@fnr.purdue.edu). – Z. Feng, Dept of Mathematics, Purdue Univ., W. Lafayette, IN 47907, USA.


Complex, human-dominated landscapes provide unique challenges to animals. In landscapes fragmented by human activity, species whose home ranges ordinarily consist of continuous habitat in pristine environments may be forced to forage among multiple smaller habitat patches embedded in an inhospitable environment. Furthermore, foragers often must decide whether to traverse a heterogeneous suite of landscape elements that differ in risk of predation or energetic costs. We modeled population consequences of foraging decisions for animals occupying patches embedded in a heterogeneous landscape. In our simulations, animals were allowed to use three different rules for moving between patches: a) optimal selection resulting from always choosing the least-cost path; b) random selection of a movement path; and c) probabilistic selection in which path choice was proportional to an animal's probability of survival while traversing the path. The resulting distribution of the population throughout the landscape was dependent on the movement rule used. Least-cost movement rules (a) produced landscapes that contained the highest average density of consumers per patch. However, optimal movement resulted in an all-or-none pattern of occupancy and a coupling of occupied patches into pairs that effectively reduced the population to a set of sub-populations. Random and probabilistic rules, (b and c), in relatively safe landscapes produced similar average densities and 100% occupancy of patches. However, as the level of risk associated with travel between patches increased, random movement resulted in an all-or-none occupancy pattern while occupied patches in probabilistic populations went extinct independently of the other patches. Our results demonstrate strong effects of inter-patch heterogeneity and movement decisions on population dynamics, and suggest that models investigating the persistence of species in complex landscapes should take into account the effects of the intervening landscape on behavioral decisions affecting animal movements between patches.