Woodland bat assemblages are usually structured in a space according to the distance from the ground, water, and obstacles, features that often define chiropteran hunting tactics. Consequently, the bat species composition differs strongly among various habitats, even within the same forest patch. However, when conducting local bat surveys in Wolin National Park (WPN), we revealed an unexpected uniformity in the qualitative and quantitative structure of bat assemblages, based on mist netting and ultrasound recording. In total, 10 vespertilionid species were detected. Across all methods and sampled habitats, a single species, Pipistrellus pygmaeus, predominated, while no Barbastella barbastellus, an old forest specialist, were detected, despite the abundance of their preferred daily roosts. We also reviewed the literature for mist-netted bat samples in four different habitats in lowland Polish forests. The samples usually clustered based on habitats, and the same habitat classes often clustered very closely despite representing geographically distant forests. The exception was WPN, where all four habitat classes formed a tightly packed cluster. We hypothesize that P. pygmaeus might act as a hyperabundant native species, a successful generalist that reduces the contribution of more specialized taxa in the assemblage. It probably benefits from both forest renaturation and anthropogenic cross-boundary subsidy.

The bat skin mites from the closely-related Demodecidae and Psorergatidae families occur synhospitally, populating the same host species and perhaps neighboring microhabitats. However, data on their occurrence and parasitism are fragmentary and dispersed. Thus far, 27 Demodecidae and 18 Psorergatidae species have been described, but the coexistence of mites from both families was only demonstrated in six species of bats. This article presents a description of Demodex pusillus sp. nov. from Nyctalus noctula, including a new host record (first observation of demodecid mites in Nyctalus) and a new record concerning the occurrence of Psorergatoides kerivoluae in Plecotus auritus. It also includes an updated global checklist of the occurrence of Demodecidae and Psorergatidae in Chiroptera, including data on their records/distribution and location in their hosts. In both studied families, the mites exhibit preferences, and even topographic specificity, colonizing different microhabitats in the host, including the eye region (e.g., Meibomian glands of the eyes, corneal surface and eyelid vault), wing membranes and hairy skin on the body. Such colonization of separate microhabitats enables different species to co-occur within the same host, while the total number of parasites determines the level of parasite load, with higher levels being associated with the incidence of disease symptoms. It is worth mentioning that Demodex pusillus sp. nov. is the smallest known representative of the Demodecidae family and one of the smallest animals (70–80 micrometers in length).

Physical obstacles within animal habitats create barriers to individual movements. To cross those barriers, specific corridors are used, some of them created by keystone species such as Eurasian beavers (Castor fiber). Their dams on rivers may also increase habitat connectivity for terrestrial mammals, but the significance of that function has never been quantified. To investigate this, we placed tracking tunnels on beaver dams, fallen trees, and—as a control—on floating rafts. Additionally, we tested kinetic sand as a novel substrate for collecting tracks and found the paws of small mustelids precisely imprinted in that medium, allowing easy identification. However, we needed to lump all shrews and rodents smaller than water voles (Arvicola amphibius) into one category as they can only be detected but not identified. The highest mammalian activity was observed on dams, as they may provide shelter, offering protection from predators during a river crossing or permanent residence, and even the opportunity to hunt invertebrates. Slightly higher diversity was found on logs because of a higher proportion of mustelids, which select exposed locations for scent marking. Our results increase our body of knowledge about the beaver as an ecosystem engineer and provide a novel tool for the monitoring of mammal activity.

Small mammal species assemble based mainly on plant communities but the structure of their assemblages is shaped by several other factors, modified by larger-scale geography. Despite their ecological significance, they are often neglected elements of biodiversity, therefore, even several Polish national parks have lacked extensive surveys. It also applies to the Wolin National Park (WNP), the only one located on a coastal marine island, known previously for its unique bat fauna. We surveyed small mammals of WNP by live- and pitfall trapping, identifying only nine species, the lowest species richness among five national parks of the region (the remaining hosted 11-13 species, based on trapping data only) and the rarefaction curve showed very low probability of increasing that number by future sampling. Such unexpected paucity of species is probably linked to insular isolation and the location of the park at the edge of regional distributions of the three species. Cluster analysis revealed the most peculiar feature of small mammal assemblages in WNP - a division of the Park into two landscape units, moraine hills and the alluvial delta, where predominant murids were, respectively, Apodemus flavicollis and Apodemus agrarius. That divergence appeared to affect the clustering more than vegetation at the trapping sites.

Woodland bat assemblages are usually structured in space by distance from the ground, water and obstacles, features often defining chiropteran hunting tactics. Consequently, bat species composition differs strongly among various habitats even within the same forest patch. However, when conducting local bat survey in Wolin National Park (WPN), we revealed unexpected uniformity in qualitative and quantitative structure of bat assemblages, based on mist netting and ultrasound recording. In total, 10 vespertilionid species were detected. In all methods and sampled habitats a single species, Pipistrellus pygmaeus, predominated, while no Barbastella barbastellus, an old forest specialist, was detected, despite the abundance of preferred daily roosts. We also reviewed literature for mist netted bat samples in four different habitats of lowland Polish forests. Samples usually clustered based on habitats and the same habitat classes often clustered very closely, despite representing geographically distant forests. The exception was WPN, where all four habitat classes formed a tightly packed cluster. We suppose that P. pygmaeus might act as a hyperabundant native species, a successful generalist that reduces the contribution of more specialized taxa in the assemblage. It probably benefits from both forest renaturation and anthropogenic cross-boundary subsidy, the latter including both roost availability and prey abundance.