Colonization processes in long-lived species: Reintroductions as experimental approach

Abstract

Understanding how density-dependent and independent processes influence demographic parameters, and hence regulate population size, is fundamental within population ecology. As Newton 1979 commented: “Effective conservation of raptors ultimately depends on a thorough understanding of what regulates their numbers”. Population regulation results from mechanisms that cause demographic density dependence: a negative feedback between population growth rate and population density (Newton, 1998). Identification of these mechanisms, as well as the way they operate, is of fundamental importance to ecology, and particularly for our understanding of colonization processes. To identify and measure these mechanisms, populations that have been reintroduced and monitored since the beginning of the process, constitute a useful source of valuable information ( Whitfield et al., 2009). Change in human attitude toward top predators is allowing an increase in distribution of previously human persecuted species. The separation model that kept wildlife in protected areas with the objective to protect wildlife from ourselves, is changing to the coexistence model as the human persecution decrease. Now a day, in Europe many recent conservation actions are related to biodiversity in human dominated landscapes. Here I analyze a Spanish Imperial eagle population in southern Spain and nighttime lights as a value of human activity from 2001 to 2015. Results show a decrease in the distance to nighttime lights over the studied period. Moreover, I found higher productivity values in territories closer to human activity. I concluded that with a change in human attitude, the availability of territory for the species is increasing and, without a direct human persecution, this new area could represent a high quality habitat for the species. Those changes will have potential influence in the selection of available habitat for species, with direct consequences in future reintroduction projects. For that, I suggest revising the habitat selection criteria for species previously human persecuted.