Density-dependent dispersal in birds and mammals

摘要: Density-dependent dispersal can be caused by various mechanisms, from competition inducing individuals to emigrate (positive density-dependence) social crowding effects impeding free movement (negative density-dependence). Various spatial population models have incorporated positively density-dependent algorithms, and recent theoretical explored the conditions for (DD) evolve. However, while existence of DD is well documented in some taxa such as insects, there no clear picture on its generality vertebrates. Here I review available empirical data birds mammals, focusing mainly variation between years experimental density manipulations. Surprisingly few studies explicitly focused DD, interpretation often hampered differences approach, small sample sizes and/or statistical shortcomings. Positive was reported 50 33% selected mammal bird studies, respectively, two mammals (out eight) negative DD. Among more emigration rates or long-distance recoveries than average distances within finite study areas. Experimental manipulating densities (mainly mammals) consistently generated positive typically showing reduced response partial removal. Studies that examined relation seasonal changes (small only) compared sites differing density, also show a mixture This suggests complex way with annual densities, these results are confounded other factors seasons sites, habitat quality. conclude both correlational support positive, rather negative, mammals.