CORRIDORS AS CONDUITS FOR SMALL ANIMALS - ATTAINABLE DISTANCES DEPENDING ON MOVEMENT PATTERN, BOUNDARY REACTION AND CORRIDOR WIDTH

Corridors are supposed to facilitate and conduct moving individuals be tween habitat remnants within an otherwise inhospitable landscape. Des pite the scientific interest in corridors, their function as conduits is open to question. In this paper we present hypothetical answers to this question based on simulations of individual movements through cor ridors. Our generic modeling approach is individual-based and spatiall y explicit. The model is designed to simulate conceivable movements of small animals through line corridors with clear boundaries such as he dgerows. The parameters of the individual movements correspond with em pirical data of tracking studies. We define the transition probability as the likelihood that moving individuals attain a distant target are a within a certain period of time. We determine the transition probabi lity based on distance frequency distributions. Our results show how t he transition probability depends on the degree of movement autocorrel ation, the returning angle at boundaries and the corridor width. In ge neral, the transition probability is essentially determined by the deg ree of movement autocorrelation. The relative importance of both the r eturning angle at boundaries and the corridor width on the transition probability increases with higher degrees of movement autocorrelation. With increasing corridor width the transition probability increases a symptotically towards an upper level depending on movement velocity an d time. Consequently, the corridor width has to be regarded as the mai n easily modified aspect for controlling transition probabilities. We use our findings to discuss the issue of an optimum corridor width. We take up the important effects of movement canalization within corrido rs and the way corridors influence both mortality en route and movemen t velocity. We compare the consequences of these effects on transition probabilities to situations without corridors in order to evaluate co rridors in a more unbiased fashion.