Titolo della tesi: La migrazione dei grandi erbivori attraverso diverse scale spazio-temporali: caratterizzazione di modelli di movimento individuali e di popolazione nel cervo canadese (Greater Yellowstone Ecosystem) e nel cervo rosso (Europa) Migration across scales – characterizing individual and population movement patterns comparing elk and red deer migration across Europe and the Greater Yellowstone
Animal movement emerges from internal individual processes in specific contexts in space and time and has consequences on individuals’ performance, population dynamics, species distribution and persistence, and ecosystem relations. Large herbivores hold key ecological functions as primary consumers and prey. Several ungulate species show ecological plasticity in movement behaviour, with a wide range of movement tactics, from long-distance migrations, to restricted movements, as responses to external drivers. Here, the ensemble of movement tactics of elk and red deer in specific environmental contexts (the Greater Yellowstone Ecosystem and diverse European landscapes), were quantified with simple, reproducible metrics, and characterised as movement expressions. Then, these metrics were related to environmental drivers at the population scale, across a wide bio-geographic range. The tortuosity of movements clearly separated elk and red deer populations, but with the exception of long-distance migratory red deer ones, that were classified together with elk populations. The Human Footprint Index was the main determinant of elk and red deer movement expression, with more tortuous movements as HFI increased, and straight movements, likely connecting discontinuous habitat patches, at very high values in Europe. These patterns were partially reflected when individual movement behaviour was analysed. Elk and red deer travelled in general in less steep landscapes, with higher vegetation predictability and less human impact than those randomly encountered, as determined by path selection analysis. Further, a strong interaction between HFI and vegetation predictability was observed, with avoidance for HFI constraining the access to profitable resources. Finally, a link between movement expression and fitness-related traits was shown in one elk herd in the GYE: currently, long-distance migrants seem to better synchronise the use of profitable resources and parturition; however, alternative movement tactics, more linked to anthropogenic landscapes, may become more prevalent in the future. This work suggests that the investigation of ungulate movement continuum and the prediction of animals’ resilience to landscape changes and global threats require a multi-scale approach, where both individual-level responses and overall patterns of movement expression are considered in ensemble.