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Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/218735
From Local to Regional: Demographic and Population Dynamics of a Long-lived Scavenger Species in a Changing Environment
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[eng] In a rapidly changing world, the loss of global biodiversity presents a significant challenge. While sustainability has become a guiding principle for balancing the protection of the environment along with economic development and human well-being, its implementation can often be disjointed across various sectors. The incoherence in the integration of environmental policies can lead to unintended negative impacts on biodiversity, particularly for vulnerable species like vultures and the environmental services they provide. Vultures, as a highly threatened group of birds, are especially vulnerable to poisoning, but also to new circular economy and renewable energy policies such as the closure of landfills and wind energy. Thus, it is imperative to evaluate the mechanisms and demographic responses of vulture species to these new paradigms. My thesis examines the demography of the griffon vulture Gyps fulvus in northeast Iberian Peninsula, using long-term data to provide a comprehensive understanding of the population dynamics in response to a changing environment. In Chapter 1, we studied how the local griffon vulture population in Central Catalonia responded to reduced organic matter in an open landfill due to European sanitary measures aimed at closing landfills. Using the robust Schwarz and Arnason Jolly-Seber model, we estimated the vultures' apparent survival probability and annual abundance. We found that the available organic matter in the landfill significantly declined after a waste treatment centre was established, negatively impacting apparent survival. However, local abundance remained stable, with an increase attributed to the growth of the Catalonian breeding population. This suggests that local waste management measures had limited impact on vultures, as their high dispersal capacity allows them to find alternative food sources. In Chapter 2, we used a Bayesian hierarchical Cormack-Jolly-Seber model to analyze the age-specific demographic response of the local vulture population at the landfill, estimating apparent survival and permanent
emigration probabilities under three scenarios of organic matter availability: no reduction, substantial decrease, and drastic decrease. We found a notable increase in transients among newly captured immatures and adults. Apparent survival in juveniles declined, while in immature residents increased and adult residents decreased. The results suggested that intensified intraspecific competition due to reduced food increased permanent emigration. However, resident immatures showed resilience, indicating that high-quality individuals persisted despite food scarcity. In Chapter 3, we used a multi-site Integrated Population Model (ms-IPM) to examine the dynamics of griffon vulture populations in Catalonia, Aragon, and the Valencian Community. We aimed to understand demographic processes and inform site-specific conservation strategies. We observed different trends: steady growth in Catalonia, stabilization in the Valencian Community after an initial increase, and a decline with a slight recovery in Aragon. Key growth factors varied by region: adult survival in Aragon, floater-to-breeder ratio and immigration in the Valencian Community, and all three factors in Catalonia. Density dependence affected the floater-to-breeder ratio and immigration in Catalonia and the Valencian Community, with higher emigration to the other two sites in the vultures of Valencian Community, likely due to nearing carrying capacity. Populations in Aragon and the Valencian Community are stable, while Catalonia is growing. Maintaining adult survival in Aragon is crucial, given its lower rate and potential non-natural mortality sources. This study highlights the value of ms-IPMs for understanding complex population dynamics and the need for targeted conservation strategies. In conclusion, by applying demographic models, including the ms-IPM, and addressing data heterogeneity and uncertainty, in this thesis we gained a deeper understanding of griffon vulture population dynamics. This approach helped identify key demographic drivers, identify possible environmental impacts, and inform conservation strategies, highlighting the need for cohesive policies across regions to effectively conserve vulnerable species like vultures.
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ARÉVALO-AYALA, Diego josé. From Local to Regional: Demographic and Population Dynamics of a Long-lived Scavenger Species in a Changing Environment. [consulta: 4 de desembre de 2025]. [Disponible a: https://hdl.handle.net/2445/218735]