| The inclusion of linear landscape elements into wildlife conservation plans has gained wide acceptance as an important aspect of conservation strategy. Despite the lack of theoretical or empirical support, biological corridors are assumed to reduce the detrimental effects of habitat fragmentation by increasing landscape connectivity. To test the hypothesis that immigration rates from a source to a target patch would be increased by the presence of a linear strip of natural vegetation ("biological corridor") in an otherwise unsuitable matrix, I created 2 strongly contrasting movement pathways in replicated field experiments. I performed these experiments with Ensatina eschscholtzi, a salamander in the family Plethodontidae. Bare pathways provided a harsh environment for Ensatina, which was reflected by lower selection (number that entered), shorter residency time (number of days), and increased velocity (greater initial distance moved) in bare than in corridor pathways. Despite these behavioral differences, I failed to detect a difference in the number of Ensatina reaching target patches ("immigrants") between corridor and bare treatments. If corridors are defined as a dispersal conduit, linear patches of vegetation in pathways failed to provide functional corridors. Identifying candidate corridor areas on conservation maps may be difficult because animals may show compensatory behavioral responses to different habitats.; I developed a heuristic model of the probability of successful dispersal to a target patch through a corridor based on results from the experiments and from the natural history of various taxa. I have depicted the relationships of the probability of successful dispersal through a corridor as the inter-relationships of 3 key species-specific parameters: selectivity of a pathway, survival costs, and movement velocity. Through this preliminary model I attempt to provide insights into animal behavioral patterns that may allow the efficacy of biological corridors to be evaluated critically on a species and site specific basis. Importantly, linear patches such as riparian areas and shelterbelts may function ecologically as habitat; there is no need to invoke a corridor function to provide a rationale for the value of such patches. |
