The direct and indirect relation between ungulates on small mammals

Abstract: Ungulates are increasing in Europe, including Sweden and can cause changes to forest structure and forest-dwelling animals. This study is focused on the relation between various ungulate species and small mammal abundance in Swedish forests, through the alteration of ground vegetation cover and directly through food competition. The relation between canopy cover and ground vegetation cover, and thus small mammals is also explored. Path analysis revealed ground vegetation cover was positively related with small mammal abundance, yet no relation was found between ungulates and ground vegetation cover and therefore no indirect relation between ungulates and small mammals. Interestingly, the significant relation between vegetation cover and small mammals was lost when the species were modelled individually, possibly due to small sample size. Certain ungulates were directly correlated with small mammals when modelled at the species level. Yellow-necked mice was positively correlated with wild boars and fallow deer densities and bank voles were negatively correlated with roe deer density. Ground vegetation cover was negatively correlated with canopy cover; thus canopy cover was indirectly negatively correlated to small mammal abundance. This study shows that vegetation cover is positively correlated with small mammals but does not suggest an indirect relation between ungulates and small mammals. The study also highlights the complexity of the studied forest ecosystem, where certain individual ungulate species directly correlate with individual small mammal species. Animal diversity, human health and ecosystems are influenced by small mammals, and vegetation cover should therefore be considered when applying management actions that increase forest biodiversity and decrease tick-borne diseases.