Human-scavenger relationsfrom conservation challenges to contributions to people

Resumen

Human activities are the main driver of global change in the Anthropocene, being responsible for the loss of biodiversity at a global scale. The loss of biodiversity alters the ecosystem functions, impacting on the contributions that nature provides to people, which condition human wellbeing. One of the most threatened functional groups are scavengers, which are related to important regulating functions in ecosystems. This thesis focuses on how human activities affect the conservation of scavenger species, whilst at the same time, delving into the multiple benefits derived from human-scavenger relations. In particular, this thesis aims to assess the following points: the response of scavenger birds to transhumant livestock activity (Chapter 1); the potential biases in the detection of poisoned wildlife (Chapter 2); the role of scavenger species in nature’s non-material contributions to people (Chapter 3); and the spatial patterns that determine the provision of non-material contributions (Chapter 4). Chapter 1 assesses the changes in the abundance of scavenger birds according to the presence of transhumant livestock, in addition to the changes in the foraging behaviour of griffon vultures (Gyps fulvus). For this purpose, we conducted field surveys to monitor changes in the abundance of scavenger birds and ungulates according to the season with presence and absence of livestock in a pastureland area of southeaster Spain where transhumant activity is still preserved. In addition, we tracked 30 griffon vultures by GPS devices, which allowed us to analyse their foraging activity in both seasons. In the presence of the livestock, there was an increase in the abundance of obligate scavengers, as well as an increase in the foraging activity of the tracked vultures. These results highlight the importance of traditional agrosystems for the conservation of obligate scavengers. In Chapter 2, a field experiment, in which animals consuming non-poisoned baits were detected by means of camera traps, was conducted in six study areas to assess potential biases in the records of poisoned wildlife. The results were compared with the poisoning records in an official database in Spain. We found that the detection of poisoned wildlife is species-dependent. Domestic animals and vultures tended to be over-represented in the database relative to those detected in the experiment, while corvids and small wild mammals were underrepresented. The differences were mediated by species traits such as size and colour. These results can provide guidance to improve strategies in the detection of poisoned wildlife. In Chapter 3, we explored different indicators to assess the role of the scavenger guild in providing non-material contributions to people in Spain. In particular, we assessed the categories of physical and psychological experiences, learning and inspiration, and the supporting identity. In addition, we explored the ecological traits of species that may determine the capacity to provide these contributions. The results showed associations among the categories, mediated by species traits. Four main groups were identified: aesthetic enjoyment experiences and contribution to knowledge through wildlife observation records, related to common species; recreational experiences and contribution to knowledge for society, related to charismatic species; contribution to scientific knowledge, associated with mesocarnivores; and supporting identity, related to species with dual roles, capable of providing both beneficial and detrimental contributions. The use of different indicators allowed to reveal the interlinkages among contribution categories and species. These findings highlight the importance of scavengers in the contributions to the human well-being. Chapter 4 explores the spatial patterns that determine the provision of non-material contributions in continental Spain. For this purpose, several indicators that assess aesthetic enjoyment experiences, recreational experiences, and contribution to scientific knowledge were mapped, and we calculated hotspots of contributions. In addition, we explored environmental factors that may condition the provision of these contributions: the presence of protected areas, the human impact index, and the richness of scavenger species. We found that protected areas, especially national parks, have a very important role in the provision of non-material contributions by scavengers, as they are preferentially developed in areas with higher species richness. Recreational experiences were associated to areas with low human impact, while aesthetic enjoyment and contribution to scientific knowledge was developed in areas with some degree of humanization. Finally, the general discussion addresses the implications of the findings in a context of global change. We also discuss the limitations identified, as well as the insights for future research addressing human-nature relations.