Mammal communities in the Anthropocene: systematic camera-trapping to study wildlife responses to anthropogenic pressures

The current epoch is unique in the history of planet Earth, for one single species, Homo sapiens, is changing profoundly and rapidly the habitats of all other living beings. In the Anthropocene, the impoverishment of the biosphere with loss of individuals and populations of non-human animals is not sparing wild mammals, whose biomass has decreased 85% compared to pre-human times. Mammals are crucial species within ecosystems, providing numerous ecological functions like vegetation structure modification, predation and prey regulation, trophic cascades, seed dispersal and the facilitation of tree establishment, scavenging and carcass removal, increase in soil complexity through burrowing, spatial niche creation, and nutrient cycling. Yet, about one quarter of the 6,500 species of mammals are currently under threat of extinction. Habitat destruction is recognized as the major driver of mammalian decline worldwide, with infrastructure networks then fragmenting and isolating the remaining habitats. Overharvesting, poaching, and wildlife trading are other important impacts on mammalian communities, especially in the southern hemisphere. Beyond these well-known impacts, new emergent threats to wildlife communities are recently rising: particular concern is roused by competition with domesticated animals and human disturbance from outdoor recreational activities, both of which are among the most reported threats in protected areas (PAs) of the northern hemisphere. These two emerging threats on mammalian communities are the two main topics of this thesis, addressed respectively in part 1 and 2. In both cases I tested ecological hypotheses by utilising systematic camera-trapping as sampling technique, a non-invasive method that allows the collection of large amounts of data on multiple species over large areas at relatively low cost. I coupled this technique with a range of analytical approaches, primarily hierarchical modelling, that allowed me to estimate important community metrics, such as spatial co-occurrence between species and multi-year trends in occurrence while accounting for the pervasive issue of imperfect detection. Furthermore, through generalised linear models I assessed the behavioural responses of species and communities to anthropogenic pressures. In Part1, chapter 1 and 2, I explored the spatio-temporal relationships between wild and domesticated mammals in four Central Asian grasslands located in the Altai mountains of western Mongolia, reconstructing potential interspecific interactions under livestock encroachment into PAs. Demand for animal products is growing globally, and also in Central Asia livestock numbers have strongly increased after the fall of the Soviet Union and the globalisation of the Cashmere wool market. Domestic herbivores have consequently become several orders of magnitude more abundant than wild ones, with indirect repercussions also on carnivores. I used two different analytical approaches to uncover the network of potential relationships that bind mammals of these communities, explicitly including the widespread presence of livestock. In part 2, chapter 3 and 4, I assessed the behavioural responses of mammalian communities in Italian mountainous PAs to the increasing trend of outdoor recreation in natural habitats. As typical in recent European environmental history, Italy has seen a natural re-expansion of forests following socio-economic changes, that coupled with legal protection and lowered persecution has allowed the re-establishment of previously rare or locally extinct medium and large mammals. Yet, the increasingly urbanised population is engaging in sports and recreational activities within natural areas, with potential disturbance on the wildlife inhabiting them, underscoring the need of monitoring the responses of animals to this human frequentation. In particular, in chapter 3 I took advantage of a long-term dataset collected with my contribution in and around an Alpine PA of western Trentino, north-eastern Italy, to estimate temporal trends in occurrence of 8 mammalian species and their spatio-temporal use of habitat under intense outdoor recreation and tourist activity. I then broadened the spatial scale of analysis in chapter 4 by targeting four PAs of the European Natura 2000 Network, and studied responses of wildlife site use to human presence in three different temporal slots, diurnal, crepuscular and nocturnal, for four mammalian communities with different species compositions.