Flexible foraging strategies in Pipistrellus pygmaeus in response to abundant but ephemeral prey

Abstract

There is growing recognition that with sympathetic management, plantation forests may contain more biodiversity than previously thought. However, the extent to which they may support bat populations is contentious. Many studies have demonstrated active avoidance of coniferous plantations and attributed this to the lack of available roost sites and low invertebrate density. In contrast, other work, carried out in plantation dominated landscapes have shown that certain bat species are able to exploit these areas. However, the extent to which bats use plantations for roosting and foraging, or simply move through the plantation matrix to access more favourable sites is unclear. We radio tracked female Pipistrellus pygmaeus over two summers to establish the extent to which individual bats use Sitka Spruce plantations in southern Scotland for foraging and roosting and assess the implications for felling operations on bats. Maternity roosts identified (n = 17) were in all in buildings and most were large (> 500 individuals). We found no evidence of bats roosting in mature Sitka Spruce crop trees, although several bats used roosts in old or dead beech and oak trees as an alternative to their main maternity roost. Home ranges were much larger (mean 9.6 ± 3.12 km2) than those reported from other studies (0.6–1.6 km2), and it is likely that roost availability rather than food abundance constrains P. pygmaeus use of Sitka Spruce plantations. At the landscape scale, most individuals selected coniferous habitats over other habitat types, covering large distances to access plantation areas, whilst at a local scale bats used forest tracks to access water, felled stands or patches of broadleaf cover within the plantation. Sitka Spruce plantations support a high abundance of Culicoides impuctatus, the Highland midge which may act as a reliable and plentiful food source for females during lactation, an energetically expensive period. The use of felled stands for foraging by bats has implications for forest management as wind turbines, following small-scale felling operations, are increasingly being installed in plantations; wind turbines have been associated with high bat mortality in some countries. Decisions about siting wind turbines in upland plantations should consider the likelihood of increased bat activity post felling.

Variability in bat morphology is influenced by temperature and forest cover and their interactions

“…It is known that soft‐bodied Nemoteceran diptera are the main components of P. pygmaeus diet (Barlow et al, 1997 ). Coniferous forest habitats support high abundances of Nemoteceran diptera, e.g., midges, and P. pygmaeus will preferentially seek out the coniferous forest for foraging (Kirkpatrick et al, 2018 ). However, we mirror the sentiments of Salinas‐Ramos, Agnelli, Bosso, Ancillotto, Sánchez‐Cordero, et al ( 2021 ), who found changes in bat jaw morphology along a latitudinal gradient and hypothesized this may be due to a key variable relating to diet being absent from the data.…”

Exceptionally Uniform Bat Assemblages across Different Forest Habitats Are Dominated by Single Hyperabundant Generalist Species

“…It also forms nursery colonies much larger than those of P. pipistrellus [85], furtherly increasing its competitive potential. Moreover, due to flexible foraging strategies, P. pygmaeus is adapted to exploit abundant but ephemeral prey, such as small midges, forming large swarms around even-aged, intensively managed plantations of non-native conifers [86]. At least when foraging in riparian and wetland habitats, P. pygmaeus hunts mostly small dipterans belonging to the family Chironomidae, i.e., one of the most abundant groups of aquatic insects, which often increase in density through the anthropogenic eutrophication of waters [87].…”

Staat van instandhouding (status en trends) van de soorten van de Habitatrichtlijn Deelrapport vleermuizen (rapportageperiode 2013-2018)

“…B07 P. pygmaeus also uses trees as day roosts (Bartonička et al 2008, Kirkpatrick et al 2018, Dietz et al 2018 9 Conservation measures…”