Cyclic voles and Puumala hantavirus in a changing boreal landscape

• Main Author: Magnusson, Magnus
• Format: Doctoral or Postdoctoral Thesis
• Language: Swedish; English
• Published: 2015
• Subjects: Zoology; Ecology; Fennoscandian; Northern Sweden
• Online Access: https://pub.epsilon.slu.se/11698/; https://pub.epsilon.slu.se/11698/1/magnusson_m_141210.pdf

Land-use change is causing extinction of species globally, while also increasing the risk of disease exposure to humans through augmented interactions with wildlife, when humans live and work in manipulated ecosystems or when animals seek shelter/refuge in man-made infrastructure. Forestry is one such activity, which is continually altering forest structure worldwide, causing habitat loss for many specialized forest species. This study investigates the population ecology of three cyclic vole species, Myodes rufocanus, Myodes glareolus and Microtus agrestis, in relation to intensive forestry in northern Sweden. M. glareolus is also the natural reservoir of Puumala hantavirus (PUUV) which is important from a public health perspective since PUUV causes nephropathia epidemica in humans. M. rufocanus and M. agrestis declined substantially in density and distribution during the 1970-80s while M. glareolus only marginally declined and is still the most common species in the region. The decline of M. rufocanus was related to habitat loss. The cumulated impact from long-term clear-cutting explained local extinctions of M. rufocanus. The species is also dependent on maintained connectivity between old forest and shelter-providing stone fields. In contrast, local extinction of M. agrestis was not related to forestry, suggesting action of another strong driver. M. agrestis re-colonized most of the study area during 2010-2011, two years that were characterised by cold winters and a thick snow cover, suggesting a climatic driver in this case. Occurrence of PUUV infected M. glareolus was negatively related to the impact of long-term clear-cutting in the surrounding landscape. PUUV infected M. glareolus survived during low density periods of the vole cycle in old forests. In summary, the main driver of the decline in density and distribution of M. rufocanus appeared to be intensive forestry. PUUV infection dynamics also appeared to be related to forestry. Since land-use changes and climate changes have coincided in Fennoscandian forests, I suggest that future studies should focus on estimating the relative impact of these two factors on pathogen and vole population dynamics.