Seguimiento y gestión de sistemas depredadores-presa : aplicación a la conservación de fauna amenazada

La depredación es un proceso natural que tiende a regular las abundancias de las especies presa y las de sus principales depredadores. Sin embargo, la actuación humana puede llevar a situaciones de riesgo tanto para los depredadores como para las presas. En la actualidad, los problemas que debe afrontar una adecuada gestión de los sistemas depredador-presa son numerosos, especialmente en los ámbitos cinegético y de conservación. No obstante, por cuestiones éticas, legales y de complejidad intrínseca, son escasos los trabajos de investigación que han abordado el problema y, por consiguiente, también muy exigua la base científica existente. Por ello, esta Tesis Doctoral aborda el tema con un planteamiento holístico, integral, que contempla aspectos diversos, pero complementarios, de la gestión de los sistemas depredador-presa y aporta tanto conocimiento científico original como posibles soluciones prácticas para algunos de dichos problemas. El primer capítulo aborda la gestión de la depredación sin control de depredadores: mediante la mejora del refugio disponible para la presa. Se desarrolla en un ámbito mediterráneo con poblaciones de conejo de baja densidad donde, además de depredadores generalistas, hay otros especialistas amenazados cuya presa principal es el conejo. Los resultados obtenidos con más de 500 refugios artificiales mostraron una ocupación elevada (~75%) tras más de un año desde su instalación y permitieron discernir las condiciones y ubicaciones que maximizarían su uso por el conejo. Los capítulos dos y tres se centran en los métodos de detección y seguimiento de meso-depredadores mamíferos. Su comportamiento mayoritariamente nocturno y elusivo, unido a la habitual escasez de medios materiales, hace que técnicas como la detección de indicios indirectos o el fototrampeo resulten especialmente apropiadas. Mediante ninguna de ellas se detectaron todas las especies de meso-carnívoros presentes. El conteo de excrementos y huellas a lo largo de estructuras lineales es un método más adecuado que el fototrampeo para la detección de zorro y marta-garduña. El foqueo nocturno proporcionó una estima correcta de la abundancia de zorro, aunque debe repetirse durante, al menos, dos noches consecutivas. Para detectar los valores máximos anuales con bajos coeficientes de variación, los muestreos deben realizarse durante los meses de mayo-agosto, sea cual sea el método elegido. De los índices de abundancia relativa estudiados (en base a conteo de excrementos), el de frecuencia de aparición podría ser adecuado para el seguimiento de poblaciones de zorro. Los métodos de control de depredadores deben ser selectivos para adaptarse a la normativa legal vigente, y así no comprometer el bienestar de las especies silvestres que se pretenden capturar y ni el del resto En el cuarto capítulo, se han evaluado tres tipos de lazos con tope para la captura en vivo de zorro. Los resultados confirman que los tres son muy selectivos, asegurando el bienestar tanto de los zorros capturados como de las especies no objetivo, por lo que superan los estándares para su homologación en España. El capítulo cinco presenta los resultados de tres años de control de zorro, marta, garduña y gato montés sobre sus propias poblaciones y sobre el éxito reproductivo del urogallo pirenaico (Tetrao urogallus aquitanicus). El efecto del control sobre el género Martes fue temporal, aunque efectivo durante los meses de nidificación y primeras fases de vida de los pollos de urogallo, mientras que el efecto no fue evidente en el caso del zorro. El éxito reproductor del urogallo es inferior al de otras poblaciones europeas y la densidad de adultos ha disminuido un 4% cada año desde 1989 hasta 2010. El análisis BACI no permite apoyar ni rechazar la existencia de un efecto del control de depredadores sobre el éxito reproductor. Aún así, en la zona con control de depredadores se logró frenar la tendencia regresiva del éxito reproductor desde 1993 y se registraron los grupos más numerosos de volantones de toda la serie temporal. El capítulo seis presenta el primer modelo de viabilidad poblacional para el urogallo pirenaico. Los análisis de sensibilidad muestran que la supervivencia de las hembras adultas es el parámetro con mayor influencia sobre la tasa finita de crecimiento. Todo parece indicar que la gestión debe centrarse en mejorar el reclutamiento. Tras las simulaciones de Monte Carlo de diferentes escenarios de gestión, las únicas estrategias que podrían considerarse eficaces son las que combinan el control de meso-depredadores terrestres con la suelta de hembras adultas criadas en cautividad. ABSTRACT Predation is a natural process that tends to regulate the abundance of prey species and their main predators. However, human intervention can lead to risks for both predators and prey. Today, the problems facing the proper management of predator-prey systems are numerous, especially in hunting and conservation areas. However, for ethical and legal reasons and due to the intrinsic complexity of this issue, few research projects have addressed the problem and therefore there is almost no scientific basis that can be used to solve the challenges faced by environmental authorities. Therefore, this PhD thesis addresses the issue using a holistic, comprehensive approach, which covers various complementary aspects, for the proper management of predator-prey systems and provides scientific knowledge and several original and practical solutions to some of these problems. The first chapter addresses the management of predation without predator control: by improving the available shelter for prey. It takes place in a Mediterranean area with low rabbit population density where, in addition to generalist predators, there are other threatened specialists whose main prey is rabbit. The results obtained from more than 500 artificial warrens showed a high occupancy (~ 75%) more than a year after their installation and enabled us to discern the conditions and locations that maximise their use by rabbits. Chapters two and three focus on methods of detecting and monitoring mammalian mesopredators. Their mostly nocturnal and elusive behaviour, together with the usual scarcity of resources, makes techniques such as indirect signs or camera trapping particularly useful. None of the techniques detected all the species of terrestrial mesocarnivore present. Counting scats and footprints along linear structures is more appropriate for the detection of red fox and marten than the use of cameras. Spotlights at night provided an adequate estimate of fox abundance, but they must be repeated for at least two consecutive nights. In order to detect the maximum annual abundance, with the lowest coefficients of variation, censuses should be performed between the months of May to August, irrespective of the method chosen. Of the studied relative abundance indices (based on scat counts), the frequency index may be appropriate for monitoring fox populations. Predator control methods must be selective, in order to comply with current Spanish legislation, and to avoid compromising the welfare of the target species and of the other wildlife species. In the fourth chapter, we evaluated three types of devices for the live capture of red foxes. The results confirm that all three are very selective, ensuring the welfare of both foxes and non-target species captured and, therefore, exceed the standards required for their authorisation in Spain. Chapter five presents the impact of three years of control of red fox, pine marten, stone marten and European wildcat populations on their these species, on their abundance and on the reproductive success of the Western capercaillie (Tetrao urogallus aquitanicus). The effect of controlling species in the genus Martes was temporary, although effective during the months of nesting and early life stages of chicks, while in the case of red fox the effect was not evident. Capercaillie breeding success is lower than in other European populations and the density of adults decreased by 4% each year from 1989 until 2010. BACI analysis does not allow us to accept or reject the existence of the effect of predator control on breeding success. Nevertheless, in the area with predator control, the declining trend in breeding success since 1993 was reversed in 2010, where we recorded the largest groups of fledglings of the entire temporal series. Chapter six presents the first population viability model for the Pyrenean subspecies of the Western capercaillie. Sensitivity analyses show that the survival of adult females is the parameter that has the greatest influence on the finite growth rate. It appears that management must focus on improving recruitment. After the Monte Carlo simulations of different management scenarios, the only strategies that could be considered as effective are those that combine the control of mesopredators with the release of captive-bred adult females

Effect of Methodological and Ecological Approaches on Heterogeneity of Nest-Site Selection of a Long-Lived Vulture

The application of scientific-based conservation measures requires that sampling methodologies in studies modelling similar ecological aspects produce comparable results making easier their interpretation. We aimed to show how the choice of different methodological and ecological approaches can affect conclusions in nest-site selection studies along different Palearctic meta-populations of an indicator species. First, a multivariate analysis of the variables affecting nest-site selection in a breeding colony of cinereous vulture (Aegypius monachus) in central Spain was performed. Then, a meta-analysis was applied to establish how methodological and habitat-type factors determine differences and similarities in the results obtained by previous studies that have modelled the forest breeding habitat of the species. Our results revealed patterns in nesting-habitat modelling by the cinereous vulture throughout its whole range: steep and south-facing slopes, great cover of large trees and distance to human activities were generally selected. The ratio and situation of the studied plots (nests/random), the use of plots vs. polygons as sampling units and the number of years of data set determined the variability explained by the model. Moreover, a greater size of the breeding colony implied that ecological and geomorphological variables at landscape level were more influential. Additionally, human activities affected in greater proportion to colonies situated in Mediterranean forests. For the first time, a meta-analysis regarding the factors determining nest-site selection heterogeneity for a single species at broad scale was achieved. It is essential to homogenize and coordinate experimental design in modelling the selection of species' ecological requirements in order to avoid that differences in results among studies would be due to methodological heterogeneity. This would optimize best conservation and management practices for habitats and species in a global context

Bosques y matorrales mediterráneos continentales

Los bosques y matorrales mediterráneos continentales españoles son ecosistemas muy originales. Lo son porque, siendo relativamente abundantes en España, están muy escasamente representados en Europa y el resto del mundo. También por sus altos niveles de endemicidad (taxones exclusivos) y biodiversidad (especies y variantes genéticas infraespecíficas, ecotonos y paisajes en mosaico). Porque son ecosistemas modelados por la acción humana desde hace milenios (paisajes culturales) y, como consecuencia, atesoran un valiosísimo patrimonio cultural. Porque, también por ello, su persistencia, y la de los servicios que proporcionan a la sociedad, dependen de esos modelos tradicionales de gestión. Incluso porque, al contrario de lo que sucede en otros ecosistemas, no están amenazados por el incremento de la población humana y la sobre-explotación sino por todo lo contrario: el abandono de la gestión y la desertización, o despoblación humana. La conservación de los bosques y matorrales mediterráneos continentales pasa por la búsqueda de nuevas alternativas de gestión extensiva, diversificada y eficiente (modelos tradicionales o similares) que permitan mantener una población humana suficientemente densa, activa e integrada (Desarrollo Rural Sostenido) que pueda garantizar la persistencia de los elementos y procesos ecológicos básicos de su entorno natural

Provision of artificial warrens as a means to enhance native wild rabbit populations: what type of warren and where should they be sited?

In Spain, wild rabbits are essential for some highly endangered species, and, therefore, many actions have been undertaken to increase their populations. In the present study, artificial warrens are provided as a means to increase shelter for native wild rabbit populations in a given area. We evaluate the use of three types of warrens by rabbits and the effect on that use of five habitat characteristics at two spatial scales (500 × 500-m grids and 25-m plots). To evaluate that use, we identified pre-established signs at the entrances to each warren, and based on this, we calculated occupancy rate and activity. Our results indicate that rabbit abundance within a grid is the only variable which simultaneously explains both the greater occupancy and the higher activity in the artificial warrens located in that grid. Some 73.2% of the grids showed signs of rabbit use at the time of the evaluation. However, the pre-existing rabbit populations within the grids were not quantified and, hence, we cannot state that the warrens contributed to an increase in the rabbit abundance. Regarding the habitat, our results reveal that warrens should be situated in grids with food coverage of less than 50%, while the use of each individual refuge is greater where food availability in the immediate surroundings is at least 20% and shelter at least 50%. The tube warrens showed significantly greater rabbit use than the other types while there was little difference between the stone and pallet warrens in terms of use

Minimising Mortality in Endangered Raptors Due to Power Lines: The Importance of Spatial Aggregation to Optimize the Application of Mitigation Measures

Electrocution by power lines is one of the main causes of non-natural mortality in birds of prey. In an area in central Spain, we surveyed 6304 pylons from 333 power lines to determine electrocution rates, environmental and design factors that may influence electrocution and the efficacy of mitigation measures used to minimise electrocution cases. A total of 952 electrocuted raptors, representing 14 different species, were observed. Electrocuted raptors were concentrated in certain areas and the environmental factors associated with increased electrocution events were: greater numbers of prey animals; greater vegetation cover; and shorter distance to roads. The structural elements associated with electrocutions were shorter strings of insulators, one or more phases over the crossarm, cross-shaped design and pylon function. Of the 952 carcasses found, 148 were eagles, including golden eagle (Aquila chrysaetos), Spanish imperial eagle (Aquila adalberti) and Bonelli's eagle (Aquila fasciata). Electrocuted eagles were clustered in smaller areas than other electrocuted raptors. The factors associated with increased eagle electrocution events were: pylons function, shorter strings of insulators, higher slopes surrounding the pylon, and more numerous potential prey animals. Pylons with increased string of insulators had lower raptor electrocution rates than unimproved pylons, although this technique was unsuccessful for eagles. Pylons with cable insulation showed higher electrocution rates than unimproved pylons, both for raptors and eagles, despite this is the most widely used and recommended mitigation measure in several countries. To optimize the application of mitigation measures, our results recommend the substitution of pin-type insulators to suspended ones and elongating the strings of insulators

A global experiment on motivating social distancing during the COVID-19 pandemic

Finding communication strategies that effectively motivate social distancing continues to be a global public health priority during the COVID-19 pandemic. This cross-country, preregistered experiment (n = 25,718 from 89 countries) tested hypotheses concerning generalizable positive and negative outcomes of social distancing messages that promoted personal agency and reflective choices (i.e., an autonomy-supportive message) or were restrictive and shaming (i.e., a controlling message) compared with no message at all. Results partially supported experimental hypotheses in that the controlling message increased controlled motivation (a poorly internalized form of motivation relying on shame, guilt, and fear of social consequences) relative to no message. On the other hand, the autonomy-supportive message lowered feelings of defiance compared with the controlling message, but the controlling message did not differ from receiving no message at all. Unexpectedly, messages did not influence autonomous motivation (a highly internalized form of motivation relying on one’s core values) or behavioral intentions. Results supported hypothesized associations between people’s existing autonomous and controlled motivations and self-reported behavioral intentions to engage in social distancing. Controlled motivation was associated with more defiance and less long-term behavioral intention to engage in social distancing, whereas autonomous motivation was associated with less defiance and more short- and long-term intentions to social distance. Overall, this work highlights the potential harm of using shaming and pressuring language in public health communication, with implications for the current and future global health challenges

A multi-country test of brief reappraisal interventions on emotions during the COVID-19 pandemic.

The COVID-19 pandemic has increased negative emotions and decreased positive emotions globally. Left unchecked, these emotional changes might have a wide array of adverse impacts. To reduce negative emotions and increase positive emotions, we tested the effectiveness of reappraisal, an emotion-regulation strategy that modifies how one thinks about a situation. Participants from 87 countries and regions (n = 21,644) were randomly assigned to one of two brief reappraisal interventions (reconstrual or repurposing) or one of two control conditions (active or passive). Results revealed that both reappraisal interventions (vesus both control conditions) consistently reduced negative emotions and increased positive emotions across different measures. Reconstrual and repurposing interventions had similar effects. Importantly, planned exploratory analyses indicated that reappraisal interventions did not reduce intentions to practice preventive health behaviours. The findings demonstrate the viability of creating scalable, low-cost interventions for use around the world

Influence of environmental factors on the breeding success of Cinereous Vultures Aegypius monachus

Breeding success determines the fate of bird populations and, therefore, understanding its determinants is an important issue for the application of conservation measures for endangered species. Breeding success depends on diverse, not mutually exclusive, effects such as the life strategies developed by species, environmental, ecological and anthropogenic factors. The influence of nest and nest tree characteristics, landscape composition and human disturbance on the breeding success of the vulnerable Cinereous Vulture Aegypius monachus in breeding colony in central Spain was analysed. A number of variables characterising the vegetation around the nest-tree, the nest-tree, and the nest itself were selected and analysed. We found that bigger and less deteriorated nests, taller nesting trees and a higher shrub coverage in a radius of 100 m around the nest resulted in an increased breeding success. Although nesting sites characteristics and nest quality can be related to birds' age and breeding experience, our findings show that geographical orientation of the slope where the nest is located as well as nest accessibility and habitat selection have an influence on Cinereous Vulture breeding success. We recommend that mature forests, steeper slopes should be carefully conserved and protected from anthropogenic disturbances in order to strengthen the conservation of breeding areas of this forest-dwelling endangered raptor species.This work was carried out within the framework of the LIFE project 03/NAT/E/0050, by CBD Habitat Foundation with the collaboration of Castilla-La Mancha, Extremadura and Madrid regional governments, and the Spanish Ministry of Environment. It was co-funded by the European Commission. A.M. was supported by a “Ramón y Cajal” research contract from the Ministry of Economy and Competitiveness (RYC-2012-11867).Peer reviewe

Assessing different management scenarios to reverse the declining trend of a relict capercaillie population: a modeling approach

2. This study analyzes the trend of the relict capercaillie population in the Spanish Pyrenees on the basis of bird densities estimated throughout the period 1989-2010, and constitutes the first attempt to modelling the dynamics of a capercaillie population in southern Europe. 3. We also explored two management actions commonly used to enhance endangered prey species, thought to be affected by hyperpredation: the release of captive-bred females, in varying numbers, the removal of terrestrial meso-carnivores and the combination of both actions, using available information from a past experience of captive breeding and from an ongoing experience of terrestrial meso-predator removal. 4. The population was declining at an annual rate of 4% for the last 20 years. Sensitivity analysis showed that recruitment (productivity+fledgling survival), rather than adult survival, was the demographic parameter which most likely could be increased by management. 5. The removal of terrestrial meso-carnivores may lead to the stabilization of the capercaillie population (lambda 0.99±0.06), although this result should be considered as preliminary. To be conservative, the only effective strategy was the combination of mesopredator removal in combination with the release of either 15, 30 or 45 adult females per year. 5. Synthesis and applications. We recommend to implement these urgency measures together with other complementary actions, as a more efficient long-term conservation strategy. The control of wild ungulate numbers, in the absence of top predators, and the removal of carcasses generated by hunting activity may lead to the self-regulation of the meso-predator guild. Decreased densities of ungulates may also prevent damages in bilberry cover, a basic resource for the species. Additionally, habitat management practices, such as the thinning of the currently encroaching tree stands, after massive depopulation of rural areas, should also be considered, for its possible role on predation rates and bilberry persistence