The seasonal trade-off between food and cover in the Alpine mountain hare (Lepus timidus)

Low structural complexity of nonnative grassland habitat exposes prey to higher predation

The structural complexity of vegetation can have profound effects on the hunting efficiency of predators, thereby affecting their intake rate of prey. While studies have shown that vegetation complexity can play an important role in managing unwanted impacts of predators, it is less clear how structural complexity of invasive vegetation affects the vulnerability of terrestrial prey. Short nonnative pasture species bred for agricultural production, for example, are highly invasive and pervade grassland ecosystems worldwide. They generally have low structural complexity compared with taller native vegetation they often displace. We conducted controlled experiments to test whether nonnative pastures expose fauna to greater predation risk. Survival of invertebrates (tethered locusts) subject to predation by invasive mammalian insectivores (European hedgehogs) in nonnative pasture (0.10 per 24 h; 95% CI, 0.08-0.13) was less than one-half that in structurally complex native perennial tussock (bunch) grass (0.24; 95% binomial CI, 0.18-0.31). A significant positive relationship was apparent between structural complexity (grass dry stem density) surrounding each locust and their survival. In a second experiment, survival of locusts placed solely in tussock increased with decreasing locust density in tussock, presumably reflecting fewer resource-rich patches on which predators could focus. These results demonstrate that invasion by structurally simple nonnative vegetation exposes prey to greater risk of predation. This is concerning from a global nature conservation perspective given that conversion of nearly one-half of the world's temperate grasslands to agriculture includes a range of invasive, structurally simple, nonnative, plant species. Minimizing invasion and maintaining and restoring complex habitat structure may be a useful conservation option for reducing unwanted predation.

Alpine glacial relict species losing out to climate change: The case of the fragmented mountain hare population (Lepus timidus) in the Alps

Alpine and Arctic species are considered to be particularly vulnerable to climate change, which is expected to cause habitat loss, fragmentation and-ultimately-extinction of cold-adapted species. However, the impact of climate change on glacial relict populations is not well understood, and specific recommendations for adaptive conservation management are lacking. We focused on the mountain hare (Lepus timidus) as a model species and modelled species distribution in combination with patch and landscape-based connectivity metrics. They were derived from graph-theory models to quantify changes in species distribution and to estimate the current and future importance of habitat patches for overall population connectivity. Models were calibrated based on 1,046 locations of species presence distributed across three biogeographic regions in the Swiss Alps and extrapolated according to two IPCC scenarios of climate change (RCP 4.5 & 8.5), each represented by three downscaled global climate models. The models predicted an average habitat loss of 35% (22%-55%) by 2100, mainly due to an increase in temperature during the reproductive season. An increase in habitat fragmentation was reflected in a 43% decrease in patch size, a 17% increase in the number of habitat patches and a 34% increase in inter-patch distance. However, the predicted changes in habitat availability and connectivity varied considerably between biogeographic regions: Whereas the greatest habitat losses with an increase in inter-patch distance were predicted at the southern and northern edges of the species' Alpine distribution, the greatest increase in patch number and decrease in patch size is expected in the central Swiss Alps. Finally, both the number of isolated habitat patches and the number of patches crucial for maintaining the habitat network increased under the different variants of climate change. Focusing conservation action on the central Swiss Alps may help mitigate the predicted effects of climate change on population connectivity.