Habitat, human pressure, and social behavior: Partialling out factors affecting large-scale territory extinction in an endangered vulture

Abstract

Extinctions are often the result of multiple factors that are difficult to disentangle and so methods for identifying simple and combined types of extinctions are valuable for both basic and applied ecology. We applied a modification of variance partitioning and a hierarchical partitioning analysis to test several hypotheses that attempt to explain the recent large-scale disappearance of Egyptian Vulture breeding territories in Spain. Our aim was to identify and then separate the simple (or pure) from the combined effects of habitat features, human pressure, and the social behavior of the species on the risk of extinction from a territory while controlling for spatial autocorrelation. Deviance partitioning showed that a complex mix of factors is significantly related to the disappearance of more than 400 territories throughout Spain. Abandoned territories were located in areas that are isolated from other conspecific territories and far from communal roost sites. In addition, these territories were found in places where there is a lack of natural habitats, high habitat fragmentation and reduced habitat diversity, and where food availability seems to be low and the illegal use of poison to control predators is a common practice. Deviance partitioning also showed an important spatial component in the probability of extinction. Abandoned territories were not randomly distributed; rather, they were aggregated in extinction 'hotspots', mainly related to food availability and human pressure. Deviance partitioning turned out to be an useful tool for identifying the relative contribution of a variety of factors -and their combined effects -associated with an extinction process.The deviance explained by each factor must be interpreted, however, in the context of a good knowledge of the life history of the species. Hierarchical partitioning can help rank conservation priorities and, by using as an objective criterion the relative weight of each independent variable that could be effectively managed for conservation, may provide wildlife managers with a means of saving funds and optimizing action plans.

Large‐scale human effects on an arid African raptor community

“…Other activities such as overgrazing or firewood collection have also been pointed out as leading causes of degradation of dry-lands, and thus, as having a negative effect on biodiversity (Wezel & Rath, 2002;Darkoh, 2003). This scenario resembles the situation in rural Europe before industrialization, when high densities of dispersed human populations and, more importantly, their negative effects through persecution and poisoning of wild animals, increased extinction rates at both local and global scales (Thompson & Jones, 1999;Brashares et al, 2001;Carrete et al, 2007). This situation might be exacerbated in the Sahel by the lack of natural refuges for wildlife, others than a few protected areas.…”

“…We performed deviance-partitioning analyses to explore the relative influence of human population, land-uses and productivity on the richness patterns at the two spatial scales (Anad´on et al, 2006;Carrete et al, 2007). This analysis allowed us to separate the pure from the joint effects of the three groups of explanatory variables on raptor richness.…”

“…HS+H+P). Lastly, we calculated the pure and joint effects (deviance explained) of human settlements, land-uses and productivity using basic algebra (Anad´on et al, 2006;Carrete et al, 2007). Once deviance-partitioning analyses assessed the relative influence of population, land-uses and productivity on the raptor richness at the two spatial scales, we identified the variables relevant within each group and their relationship (i.e.…”

Out of sight, out of mind? Testing the effects of overwinter habitat alterations on breeding territories of a migratory endangered species

“…Some management actions only aim to palliate specific problems faced by the species (Carrete et al, 2007). For example, temporary bans issued during critical periods (i.e.…”

“…European populations winter in sub-Saharan Africa, within the 14°-17°N belt (Don azar et al, 2002b;Garc ıa-Ripoll es & L opez-L opez, 2011). During the 20th century, the population of this long-lived scavenger has steadily declined across large parts of its European and African range (Carrete et al, 2007). The causes of this decline are diverse: high adult mortality due to poisoning (Cort es-Avizanda, Ceballos & Don azar, 2009;Hern andez & Margalida, 2009); collisions with man-made infrastructures (wind turbines and power lines; Carrete et al, 2009); electrocution; habitat loss (Velevski et al, 2015); habitat change (Mateo-Tom as & Olea, 2015); food shortages; and human disturbance at breeding sites are among the main threats to the species (Margalida et al, 2012;Sanz-Aguilar et al, 2015;Don azar et al, 2016).…”