Laurent Tillon

Forests offer important refuge to bats by providing attractive roosting and foraging habitats. Their conservation is a major responsibility of forest managers. The use of tree cavities by bats in forests depends on the specific demands of each species, with a large range of different types of microhabitats utilised, from degraded cavities such as peeling bark to healthy hollows in live trees ensuring the temporal stability of the habitat. The conservation of tree-dwelling bats should not be dissociated from their fission-fusion behaviour which involves the use of many different roosts. Conservation measures must therefore take into account forest habitats suitable for feeding and in particular, forest parameters such as structure, composition, vegetation and foliage, among other elements such as deadwood, all upon which the forest manager can intervene. Acting in favour of bats requires close consideration of their complex individual responses concerning roost selection and foraging habitat selection, which is largely dictated by the reproductive status of individuals. Thereafter it is possible to evaluate the impact of wood harvesting on bats and to infer silvicultural conservation measures. The implementation of recommendations must then subsequently be based on a strong involvement on the part of the forest manager.

Trees are the main roosts for several European bat species but forestry practices are most often detrimental for them. After checking for the presence or absence of bats in trees, we collected a number of variables to describe trees within a lowland sub-Atlantic oak-dominated forest. We modelled the usage of the trees by bats according to the main characteristics of trees (11 quantitative and 13 qualitative variables) with a logistical regression analysis. Our results show that the number of cavities in the tree is the main variable that induces the occupancy by bats. There is a “typical” lowland tree preferred by bats which is a healthy oak tree of large diameter. We finally provide some guidance for woodland managers to maintain bat roosts, including maintaining some trees of large diameter, protecting small areas of old trees with cavities).

The Eurasian red squirrel (Sciurus vulgaris) is the only naturally occurring tree squirrel throughout its range. We aim at improving current knowledge on its macroparasite fauna, expecting that it will have a poor parasite diversity because in species that have no sympatric congeners parasite richness should be lower than in hosts sharing their range with several closely related species, where host-switching events and lateral transmission are promoted. We examined gastro-intestinal helminth and ectoparasite communities (excluding mites) of, respectively, 147 and 311 red squirrel roadkills collected in four biogeographic regions in Italy and France. As expected, the macroparasite fauna was poor: we found five species of nematodes and some unidentified cestodes, three fleas, two sucking lice and two hard ticks. The helminth community was dominated by a single species, the oxyurid Trypanoxyuris (Rodentoxyuris) sciuri (prevalence, 87 %; mean abundance, 373 ± 65 worms/host). Its abundance varied among seasons and biogeographic regions and increased with body mass in male hosts while decreased in females. The most prevalent ectoparasites were the flea Ceratophyllus (Monopsyllus) sciurorum (28 %), whose presence was affected by season, and the generalist tick Ixodes (Ixodes) ricinus that was found only in France (34 %). All the other helminths and arthropod species were rare, with prevalence below 10 %. However, the first record of Strongyloides robustus, a common nematode of North American Eastern grey squirrels (S. carolinensis), in two red squirrels living in areas where this alien species co-inhabits, deserves further attention, since low parasite richness could result in native red squirrels being particularly vulnerable to parasite spillover.