Simple Summary Mediated through functional and numerical responses, the community structure and diversity of small mammal communities over the long term may show the influences of climate change, landscape changes and local disturbances. We present an overview of small mammal trapping and owl pellet analysis results in pre- and post-soviet Lithuania (the most southerly of the three Baltic States, Northern Europe), covering the period 1975-2021. All available sources, including grey literature, were included where the raw data were available. Based on the decades-long period, we analysed diversity changes and proportions within the main trophic groups. Diversity increase and dominance decrease occurred in the aftermath of changes within the country in 1990 and have not subsequently changed. Thus, there are two periods-before and after large-scale agricultural changes in the country. The proportions of the trophic groups changed gradually: a large increase in granivores coincided with a decrease in omnivores and insectivores, while the proportion of small herbivorous mammals increased less notably. The structure and diversity of small mammal (SM) communities over the long term may show the influences of climate change, landscape changes and local disturbances. We review published data regarding SM trapping and owl pellet analysis from Lithuania (the most southerly of the three Baltic States, Northern Europe), covering the period 1975-2021. Over decades, we analysed trends in the diversity of SM communities and the proportions of species and proportions of trophic groups. The large increase in granivores, from 6.9% in 1975-1980 to 45.4% in 2011-2020 and 54.7% in 2021, coincided with a decrease in omnivores and insectivores. The proportion of herbivores increased less notably. At the species level, significant decreases in the proportions of M. arvalis, C. glareolus and S. araneus were accompanied by notable increases in the proportions of A. flavicollis and A. agrarius, the latter from 1.0% in 1975-1980 to 25.3% in 2021. Concluding, two periods were identified, specifically before the 1990s and subsequently. In the second period, in the aftermath of land-use changes within the country in 1990, diversity increased, and dominance decreased, a situation that has not subsequently changed. Not excluding the concomitant effects of climate change, we relate these patterns to the alterations in habitat and anthropogenic impact.
