Response of bat species to sylvo-pastoral abandonment

Abstract

a b s t r a c tWe assessed the effect of abandonment of sylvo-pastoral practices in chestnut orchards (Castanea sativa) on bats in southern Switzerland to determine practical recommendations for bat conservation. We compared bat species richness and foraging activities between traditionally managed and unmanaged chestnut orchards, testing the hypothesis that managed orchards provide better foraging opportunities and harbour more bat species. Echolocation calls of foraging bats were sampled simultaneously at paired sites of managed and unmanaged orchards using custom made recorders. Vegetation structure and aerial insect availability were sampled at the recording sites and used as explanatory variables in the model. In a paired sampling design, we found twice the number of bat species (12) and five times higher total foraging activity in the managed chestnut orchards compared to the unmanaged ones. Bat species with low flight manoeuvrability were 14 times more common in managed orchards, whereas bats with medium to high manoeuvrability were only 5 times more common than in abandoned orchards. The vegetation structure was less dense in managed orchards. However, management did not affect relative insect abundance. Bats primarily visited the most open orchards, free of undergrowth. As a result of restricted access into the overgrown forests, the abandonment of chestnut orchards leads to a decline in bat species richness and foraging activities. Continued management of chestnut orchards to maintain an open structure is important for the conservation of endangered bat species in the southern Swiss Alps.

From field surveys to LiDAR: Shining a light on how bats respond to forest structure

“…Moreover, Obrist et al (2011) showed experimentally that foliage density only weakly (≈5%) 334 attenuates calls at frequencies between 20-60 kHz, and the bat species we studied are not known to 335 change call frequency substantially in relation to the habitat they preferably use. Of more concern is 336 the likelihood that bats may reduce call intensity when flying in dense vegetation, making them less 337 likely to be detected.…”

Ecosystem Services from Small Forest Patches in Agricultural Landscapes

“…[54,55] for fungus species diversity). Forest management and the creation of novel forest habitats such as parks do not always have a negative effect on forest biodiversity, as the optimization of stand structure can result in SFP that support a high diversity of vascular plants [56,57], insects [58,59] and bats [60,61]. The positive effect of management on biodiversity, however, is generally driven by the increase of habitat generalists or open habitat species [43,62].…”

Factors underlying migratory bat aggregations in chestnut groves

“…Abandoned groves quickly become invaded by other tree species and disappear entirely within decades as they evolve into dense mixed forests (Conedera et al 2000). In a parallel study we found twice the number of bat species (12) and 5 times higher total foraging activity in managed chestnut orchards compared to unmanaged ones, this effect being particularly pronounced in bat species with low flight manoeuvrability (Obrist et al 2011). Large mature chestnut trees very often have rotten trunks and branches, offering an exceptional variety of cavities (Spada et al 2008) for many treedwelling species (Moretti et al 2003(Moretti et al , 2004.…”

“…We suggest that this pattern is triggered by social factors related to the mating behaviour of the species that can be primarily explained by flight constraints. With their long, narrow wings (relatively small wing area and high wing loading), Leisler's bats are among the fastest-flying bats (Obrist et al 2011), a trait possibly crucial for long-distance migration and foraging, which however dramatically reduces flight manoeuvrability. During the courtship season, constraints in manoeuvrability might prove a limitation when Leisler's bat males engage in display flights to attract mates to their roosts.…”

“…According to the first hypothesis we expected Leisler's bat to select foraging sites in managed chestnut groves near to the roosts, either because this habitat provides more food (Gruebler et al 2008) or because it is more accessible to these fast-flying bats with high wing loading (Obrist et al 2011). According to the second hypothesis, we expected Leisler's bat at these stopover sites to select cooler roosts in managed stands which would enable energy-efficient resting in torpor during the day (e.g.…”