Population Models: Flexibility, Advances, and Applications to Wildlife Conservation. The Bonelli’s Eagle as a Study Case

[eng] In this thesis, we took advantage of recent advances in the degree of sophistication and flexibility of population models to study the population dynamics and conservation of long-lived species. As main objective, we aimed at understanding the effects of permanent emigration in the estimation of survival from mark-recapture analyses and its multiple implications for the interpretation of population dynamics and the reliability of population viability projections. In second term, we aimed at generating evidence-based knowledge based on quantitative population analysis to guide the management of long-lived raptors. To address these issues, we used two populations of the long-lived Bonelli’s eagle as study cases (Catalonia and Mallorca, western Mediterranean), for which extensive demographic and ecological data were available. The thesis was divided into the four following chapters. In Chapter 1, we implemented individual-based population viability analyses (PVA) to evaluate the effectiveness of different release strategies used in the reintroduction of the Bonelli’s eagle in Mallorca. Our results suggested that relocating wild-reared nonjuvenile raptors from natural populations to reintroduction areas may better favour reintroduction success in comparison to more expensive, widely implemented alternatives based on captive breeding. The better performance of relocations was related to their capacity to promote early reproduction in the reintroduction area, which may enhance population growth. In Chapter 2, we developed a spatially-explicit capture-mark-recapture model adapted to the multistate formulation to separate true survival and permanent emigration in longlived species. In addition, we compared the obtained stage-structured true survival estimates to apparent survival estimates. Our results showed that the magnitude of the differences between true and apparent survival may vary across population stages in longlived species (i.e., age, sex, breeding status) because of intrapopulation variation in the effect of permanent emigration. In addition, our findings suggested that the use of heavytailed distributions to model natal dispersal may provide more effective separations of true survival and permanent emigration in cases of mark-recapture data limited to restricted study areas. In Chapter 3, we integrated the model developed in chapter 2 into a spatially-explicit Integrated Population Model (SEIPM) aimed at insightfully describing the long-term dynamics of the Bonelli’s eagle population in Catalonia (1986-2020) and extracting relevant knowledge for long-lived species demography. The use of SEIPMs enabled an explicit estimation of emigration, immigration, and sink-source status along time, together with key demographic parameters and the dynamics of relevant population stages. Our results allowed a deep understanding of the retrospective dynamics of the study population and revealed new insights about the long-term variations of sink-source status and floater populations in long-lived species. In Chapter 4, we used the estimates of apparent and true survival from chapter 2 to compare the outcomes of PVAs using both types of estimates and their respective fits to census data. In addition, we explicitly modelled emigration and immigration to evaluate how these processes may improve or decrease the fits of PVAs based on each type of survival estimate. Our results suggested that each of both survival types may only provide accurate PVA projections in specific population scenarios where emigration and immigration match the particularities of each type of estimate. Thus, we emphasized the importance of either modelling migration processes or using calibration to real data for accurate PVA outcomes. In conclusion, this thesis provided useful extensions of demographic models for the estimation of true survival and the fine-scale study of population dynamics in long-lived species. In addition, important insights were revealed about the reliability of PVA outcomes relative to the characteristics of survival estimates. Finally, the thesis emphasized the relevance of generating evidence-based knowledge from the analysis of quantitative data for conservation decision-making.[cat] Aquesta tesi utilitza els avenços recents en el grau de sofisticació i la flexibilitat dels models poblacions per a generar coneixement rellevant per a l’estudi de la dinàmica de poblacions i la conservació d’espècies de vida llarga. Com a objectiu principal, la tesi se centra en entendre els efectes de la migració permanent en l’estimació de supervivència en anàlisis de captura-recaptura, així com els efectes que això pot tenir per a la interpretació de la demografia, les estimes de viabilitat, l’estat de conservació i la gestió de les poblacions de vida llarga. En segon pla, la tesi se centra en generar coneixement basat en evidències quantitatives per guiar la gestió d’aus rapinyaires de vida llarga. Per afrontar aquests objectius, hem utilitzat com a casos d’estudi dues poblacions de l’àliga perdiguera (Catalunya i l’illa de Mallorca), de les quals es disposa d’una extensa quantitat de dades de seguiment demogràfic i ecològic. La tesi s’ha dividit en els següents capítols: Al Capítol 1, es van desenvolupar anàlisis de viabilitat poblacional basades en individus (PVA) per avaluar l’efectivitat de les diferents estratègies d’alliberament emprades en la reintroducció de l’àliga perdiguera a Mallorca. Els resultats suggerien que la translocació d’individus no-polls salvatges d’altres poblacions cap a l’àrea de reintroducció afavoria l’èxit de la reintroducció en comparació amb altres metodologies més cares basades en la cria en captivitat. Aquesta major efectivitat estava lligada a la capacitat de les translocacions de no-polls d’accelerar una ràpida reproducció a l’àrea d’estudi, fet que promovia un ràpid creixement poblacional. Al Capítol 2, vam desenvolupar models de captura-recaptura espacialment explícits adaptats a la formulació multi-estat per estimar separadament supervivència real i migració permanent en espècies de vida llarga. Les estimes de supervivència real obtingudes, estructurades per fracció poblacional, van ser comparades amb estimes de supervivència aparent. Les comparacions mostraven que aquestes diferències variaven en intensitat al llarg de les diferents fraccions (edat, sexe, estat reproductor) degut a variacions intrapoblacionals en l’efecte de la migració permanent. Per altra banda, els nostres resultats suggereixen que l’ús de distribucions estadístiques de cua ampla per modelar dispersió natal poden ajudar a separar supervivència real i migració permanent de manera més efectiva quan les dades disponibles sobre captura-recaptura estan restringides a l’àrea d’estudi. Al Capítol 3, vam incorporar el model desenvolupat al capítol 2 dins un model integrat poblacional espacialment explícit (SEIPM) amb l’objectiu de descriure detalladament la dinàmica de la població d’àliga perdiguera a Catalunya durant les darreres quatre dècades (1986-2020), i extreure coneixement general rellevant sobre la demografia de les espècies de vida llarga. L’ús de SEIPMs va permetre una estimació explícita dels processos d’immigració i emigració, així com de l’estat font-embornal de la població al llarg del temps, juntament amb paràmetres demogràfics clau i la dinàmica d’importants fraccions poblacionals. Els resultats van permetre entendre detalladament la dinàmica retrospectiva de la població, i van revelar nous aspectes sobre la demografia de les poblacions flotants i les dinàmiques font embornal a llarg termini. Al Capítol 4, vam emprar les estimes de supervivència aparent i real del capítol 2 per comparar els resultats de PVAs basats en ambdós tipus d’estimes i el respectiu ajust de cada model a dades reals de cens. A més, vam modelar de manera explícita emigració i immigració per avaluar com aquests dos processos poden millorar o empobrir l’ajust dels models basats en els dos tipus d’estima de supervivència. Els resultats mostraven que ambdues supervivències només tenien capacitat de generar estimes precises de viabilitat en escenaris poblacionals específics on els processos d’emigració i immigració tinguessin unes magnituds molt concretes. En conseqüència, vam subratllar la importància de modelitzar processos migratoris dins els PVAs - o bé de calibrar els resultats amb dades reals - per millorar la fiabilitat d’aquests models. En resum, en aquesta tesi s’han desenvolupat extensions de models poblacionals per a l’estimació de supervivència real i l’estudi detallat de les dinàmiques poblacionals en espècies de vida llarga. A més, la tesi ha aportat troballes importants sobre la fiabilitat i la precisió dels PVAs segons les particularitats de les estimes de supervivència emprades. Finalment, s’hi ha destacat la importància de generar coneixement basat en l’evidència científica per a la gestió de poblacions salvatges a través de models poblacionals

Raptor reintroductions: Cost-effective alternatives to captive breeding.

Reintroductions are becoming a popular tool to prevent extinctions, although their overall success rate is low. Assessing the efficiency and cost-effectiveness of different reintroduction strategies may help identify and promote efficient practices. Captive-breeding is widely used in animal reintroductions, although concerns have been raised about relatively high failure rates and economic costs. Here, we compared the effectiveness of two simultaneously used strategies in the reintroduction of the Bonelli's eagle on the island of Mallorca: The release of captive-bred chicks and wild-reared, translocated non-juveniles. To do so, we estimated the main vital rates for individuals released by both strategies and used these to perform population simulations to assess their overall performances. The use of wild-reared nonjuveniles showed a trend with higher numbers of breeding pairs 10 years after the end of releases (14.75 pairs, 95% CI 4-25 vs. 11.21 pairs, 95% CI 2-24) and was the only strategy that prevented extinction in the long term. Following that, based on cost estimations of every strategy and different reintroduction budgets, we assessed the cost-effectiveness of releasing wild-reared non-juveniles compared with two captive-breeding alternatives: Releasing chicks either originally from breeding programmes or extracted from nests in natural populations. Again, releasing wild-reared non-juveniles was the only strategy that prevented long-term extinction in all economic scenarios (i.e. low-budget scenario 21.49 pairs, 95% CI 2-25). The use of chicks sourced from captive-breeding programmes did not guarantee long-term persistence even in high-budget scenarios (14.50 pairs, 95% CI 0- 25). Releasing wild-reared non-juveniles boosts early recruitment to the breeding population and early reproduction, which can be key for reintroduction success. However, in some scenarios, post-release effects can be stronger in wild-reared individuals, especially because of high translocation stress and post-release dispersal. Hence, we recommend undertaking careful evaluation of the pros and cons of every strategy and embracing adaptive management to choose best strategies

Joint estimation of survival and dispersal effectively corrects the permanent emigration bias in mark‑recapture analyses

Robust and reliable estimates of demographic parameters are essential to understand population dynamics. Natal dispersal is a common process in monitored populations and can cause underestimations of survival and dispersal due to permanent emigration. Here, we present a multistate Bayesian capture-mark-recapture approach based on a joint estimation of natal dispersal kernel and detection probabilities to address biases in survival, dispersal, and related demographic parameters when dispersal information is limited. We implement this approach to long-term data of a threatened population: the Bonelli's eagle in Catalonia (SW Europe). To assess the method's performance, we compare demographic estimates structured by sex, age, and breeding status in cases of limited versus large data scales, with those of classical models where dispersal and detection probabilities are estimated separately. Results show substantial corrections of demographic estimates. Natal dispersal and permanent emigration probabilities were larger in females, and consequently, female non-breeder survival showed larger differences between separate and joint estimation models. Moreover, our results suggest that estimates are sensitive to the choice of the dispersal kernel, fat-tailed kernels providing larger values in cases of data limitation. This study provides a general multistate framework to model demographic parameters while correcting permanent emigration biases caused by natal dispersal

Assumptions about survival estimates and dispersal processes can have severe impacts on population viability assessments

Population viability analysis (PVA) is a central tool for conservation decision-making. To ensure the reliability of PVA projections, it is important to identify factors that can introduce biases. This study addresses two general but overlooked related issues in PVAs that can significantly affect the reliability of their projections. First, we examined the effects of using apparent versus true survival estimates on PVA outcomes. Second, we incorporated emigration and immigration into the models to assess their influence on the accuracy of projections based on each type of survival estimate. To evaluate these concerns, we implemented PVAs structured by age, sex, and breeding status using as a study system a threatened raptor population (Bonelli's eagle, Aquila fasciata) from which apparent and true survival were available (2008–2020). The performances of PVA projections based on each survival type and dispersal process were assessed by evaluating their fit to census data. Our findings revealed that using apparent survival underestimated census data, while true survival showed a considerably better fit. However, models including dispersal processes showed that each survival type may only deliver precise projections at very specific levels of emigration and immigration. Given the potentially large differences found when using true and apparent survival, we suggest that the relevance of this issue should be elevated to that of other widely reported PVA limitations. Recently developed, accessible analytical methods may permit an easier estimation of true survival and dispersal processes. Otherwise, calibrating projections against observed data may be fundamental to test the adequacy of survival estimates

Assumptions about survival estimates and dispersal processes can have severe impacts on population viability assessments

Population viability analysis (PVA) is a central tool for conservation decision-making. To ensure the reliability of PVA projections, it is important to identify factors that can introduce biases. This study addresses two general but overlooked related issues in PVAs that can significantly affect the reliability of their projections. First, we examined the effects of using apparent versus true survival estimates on PVA outcomes. Second, we incorporated emigration and immigration into the models to assess their influence on the accuracy of projections based on each type of survival estimate. To evaluate these concerns, we implemented PVAs structured by age, sex, and breeding status using as a study system a threatened raptor population (Bonelli's eagle, Aquila fasciata) from which apparent and true survival were available (2008–2020). The performances of PVA projections based on each survival type and dispersal process were assessed by evaluating their fit to census data. Our findings revealed that using apparent survival underestimated census data, while true survival showed a considerably better fit. However, models including dispersal processes showed that each survival type may only deliver precise projections at very specific levels of emigration and immigration. Given the potentially large differences found when using true and apparent survival, we suggest that the relevance of this issue should be elevated to that of other widely reported PVA limitations. Recently developed, accessible analytical methods may permit an easier estimation of true survival and dispersal processes. Otherwise, calibrating projections against observed data may be fundamental to test the adequacy of survival estimates

Egyptian Vulture CR data

This dataset was used to analyze survival probabilities of Egyptian Vultures at Canary Islands from 1998 to 2017.We acknowledge financial support through the projects REN 2000–1556 GLO, CGL2004-00270/BOS, CGL2009-12753-C02-02, CGL2012-40013-C02-01, and CGL2015-66966-C2-1-2-R (Spanish Ministry of Economy and Competitiveness and EU/FEDER).The data file contains capture, resight and recovery histories of Egyptian vultures at Canary Islands (Fuerteventura and Lanzarote) during breeding seasons 1998 to 2017. This file contains one line per individual; one column per encounter occasion (from column 1 to 20 were code “0” indicate that the individual was not observed in a particular year; code “1” is used for individuals detected (marked at capture or resighted) with both coloured and steel metal butt-end rings; code “2” is used for individuals detected (marked at capture or resighted) with coloured and steel metal lock-on rings; code “3” is used for individuals resighted only retaining their coloured rings, code “4” is used for individuals resighted only retaining steel metal butt-end rings; and code “5” is used for individuals recovered freshly dead. There are six further columns (21 to 26) indicating the group (starting age at marking form 1-year-old to ≥6 year-old) for each individual.N

Evaluating European LIFE conservation projects: Improvements in survival of an endangered vulture

Long-lived avian scavengers are threatened worldwide and thus, are common targets of conservation plans. However, scientific evidence of both the factors limiting populations and effectiveness of management actions are greatly needed in order to develop more efficient and successful conservation strategies. We assessed the effectiveness of conservation actions applied within a LIFE-Nature project aimed at improving the long-term survival of the critically endangered Canarian Egyptian vulture: including education campaigns for public awareness and control of illegal poisoning and the modification of power lines to reduce the risk of accidents. We formulated a multievent capture–mark–recapture model to obtain estimates of survival for juvenile, subadult and adult birds accounting for probabilities of resight, recovery and losses of metal and colour rings. Models supported a substantial enhancement in survival for subadult and adult birds and a moderate improvement for juveniles after the implementation of LIFE actions. Ring loss probabilities became notably high in the middle to long term. Poisoning events became very rare after LIFE was implemented, suggesting a positive effect of environmental education and awareness campaigns. Entanglements and collisions in power lines were also efficiently mitigated. Instead, electrocutions became the most identified cause of death in the post-LIFE stage. Synthesis and applications. Our results highlight the improvement of survival in a threatened island vulture population after the implementation of a European LIFE conservation project. On small islands, with small human populations and few stakeholders, education and awareness campaigns can be especially effective for biodiversity conservation. We also demonstrate the need to complement conservation programmes with long-term monitoring, which is essential to evaluate the effectiveness of actions, especially for long-lived species.Peer reviewe

Identifying conservation priority areas for the Andean condor in southern South America

Mobile species face an array of human threats across political boundaries, and their protection relies on identifying and prioritizing areas for conservation. Large avian scavengers are one of the widest ranging and most threatened species globally, and efforts to preserve them have come to the forefront of wildlife management. Vultures require access to functionally distinct habitats for roosting, foraging and flying, yet behavior-specific habitat modelling has been overlooked in management planning. Herein, we developed a spatial prioritization model for the threatened Andean condor (Vultur gryphus) that integrates activity-specific habitat selection across heterogeneous landscapes. We tracked 35 individuals in two regions of Argentina and Chile differing in topography and vegetation composition, and analyzed how landscape covariates influence where condors roost, forage and fly, while accounting for individual differences. We found that individuals responded differently to environmental covariates during each behavior, and identified regional differences for some covariates dependent on behavioral state. We also found important individual differences in habitat selection between birds inhabiting each region. We combined these results into an ensemble spatial prioritization model, and found that most areas of high priority for Andean condor conservation are not under protection. The strategic implementation of conservation measures in these priority areas could have important implications for the recovery of this species. Our study illustrates the value of integrating behavioral- and individual-specific habitat analyses into spatial conservation planning, and points to opportunities for effective management of threatened vultures.Fil: Perrig, Paula Leticia. University of Wisconsin; Estados UnidosFil: Lambertucci, Sergio Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Cruz, Jennyffer. University of Wisconsin; Estados UnidosFil: Alarcón, Pablo Angel Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Plaza, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Middleton, Arthur. University of California at Berkeley; Estados UnidosFil: Blanco, Guillermo. Consejo Superior de Investigaciones Científicas. Museo Nacional de Ciencias Naturales; EspañaFil: Sánchez Zapata, José. Universidad de Miguel Hernández; EspañaFil: Donázar, José. Consejo Superior de Investigaciones Científicas. Estación Biológica de Doñana; EspañaFil: Pauli, Jonathan Nicholas. University of Wisconsin; Estados Unido