Modeling the consequences of the demise and potential recovery of a keystone-species: wild rabbits and avian scavengers in Mediterranean landscapes

Abstract

Restoration of demised keystone-species populations is an overriding concern in conservation biology. However, since no population is independent of its environment, progress is needed in predicting the efficacy of restoration in unstable ecological contexts. Here, by means of Population Dynamics P-system Models (PDP), we studied long-term changes in the population size of Egyptian vultures (Neophron percnopterus) inhabiting a Natural Park, northern Spain, to changes in the numbers of wild rabbits (Oryctolagus cuniculus), a keystone-species of Mediterranean ecosystems that have suffered >90% population decline after a hemorrhagic disease outbreak. Low availability of rabbit carcasses leads Egyptian vultures to extend their foraging activities to unprotected areas with higher non-natural mortality whereas growing numbers of griffon vultures (Gyps fulvus), a dominant competitor, progressively monopolize trophic resources resulting in a focal population decrease. Modeling shows that, even if keystone-species populations recover in core protected areas, the return to the original studied population size may be unfeasible, due to both the high non-natural mortality rates in humanized areas and long-term changes in the scavenger guild structure. Policy decisions aimed to restore keystone-species should rely on holistic approaches integrating the effects of spatial heterogeneity on both producer and consumer populations as well as within-guild processes.

Sex- and age-dependent patterns of survival and breeding success in a long-lived endangered avian scavenger

“…The density-dependent age of recruitment hypothesis predicts that individuals can advance the age of first reproduction when vacancies exist in the population, with recruitment serving as a buffering mechanism allowing persistence30. Our focal population is under clear decline linked to unnatural high mortalities313233 but still showed a substantial delay in recruitment. Although a high plasticity in age of first reproduction is a common trait among long-lived species, early reproduction has been commonly associated with increased mortality and/or breeding costs1634.…”

Spatial and temporal movements in Pyrenean bearded vultures (Gypaetus barbatus): Integrating movement ecology into conservation practice

“…This implies that bearded vultures spend a significant amount of time foraging outside protected areas, thereby increasing the inherent risks of non-natural mortality due to anthropogenic factors46. Biodiversity conservation strategies are increasingly focused on regions outside protected areas, where animals face numerous anthropogenic threats and have to coexist with human settlements, livestock and agriculture47.…”

“…Biodiversity conservation strategies are increasingly focused on regions outside protected areas, where animals face numerous anthropogenic threats and have to coexist with human settlements, livestock and agriculture47. As a result, an increase in conservation actions outside protected areas is a priority in any attempt to reduce the risk of non-natural mortality46. Of non-natural mortality factors, the risk of ingesting poison bait is one of the most serious factors affecting bearded vultures36 and other avian scavengers4849505152 around the world.…”

Ecosystem‐level effects of keystone species reintroduction: a literature review

“…Translocation has three forms: (1) Introduction: intended or unintended movement of an organism out of its native range; (2) Reintroduction: intended movement of an organism into native range from which it has been extirpated; and (3): Restocking: movement of members of a species to augment the number of individuals in an original habitat (IUCN ). Managers have increasingly used keystone species translocations as a tool for conservation benefits, such as restoration of important processes to ecosystems (IUCN/SSC ; Cortés‐Avizanda et al ; Plein et al ).…”

“…Literature reviews that focus on keystone species typically address the function of species in their ecosystems (Kotliar et al ; Janiszewski et al ), the definition of keystone species (Mills et al ; Kotliar ; Mouquet et al ), or methods of reintroduction (Truett et al ). Because keystone species reintroduction is proposed as a conservation tool (Cortés‐Avizanda et al ; Plein et al ), we desired to review and synthesize the extent, efficacy, and success of keystone species reintroductions. Furthermore, we sought to ascertain the current state of knowledge of the ecosystem‐level effects (i.e.…”