Effect of climatic and palaeoenvironmental changes on the occurrence of Holocene bats in the Swiss Alps

Abstract

A large-scale palaeozoological study compared 45 14C-dated bat remains from the southern and northern Swiss Alps with palaeovegetational and palaeoclimatic data. Four thermophilous (warm-demanding) and four psychrophilous (cold-tolerant) bat species, mainly forest dwellers, were selected for the study. Myotis blythii is the oldest bat species recorded in the Alps, i.e. on the southern side, going back to the early Holocene at 10 500 cal. BP. Our study showed that thermophilous species (e.g. Myotis bechsteinii and Rhinolophus hipposideros) were most abundant during the Holocene climatic optimum in Central Europe (10 000—4000 cal. BP), when warm-demanding mixed forests were dominant. Psychrophilous species such as Myotis brandtii also occurred during the climatic optimum, but most of the samples fall into the onset of the late Holocene (Sub-Atlantic period), when summer temperatures were already declining. These species declined in the southern Alps after 4000 cal. BP, when fire was intensively used by humans to convert portions of the forest into open land. This fire practice modified forest species composition and structure, with effects on forest-dwelling bat communities. We conclude that during the early and mid Holocene bat community compositions mainly depended on climate and related vegetation and forest structure dynamics. With increasing land use during the mid and late Holocene, anthropogenic changes of forest composition and creation of open habitats increasingly co-determined bat-population dynamics in the Alps. These Swiss findings are in agreement with previous results from eastern Central Europe.