Hard Forest Edges Act as Conduits, Not Filters, for Bats

Abstract

High levels of bat activity have been reported at forest edges worldwide, but few studies have examined the ecological function of edges as a linear landscape feature. Patterns of association of bats at edges between old and young forest stands (hard edges) could be a result of edges acting as either a semi‐permeable barrier or a filter to movement into the forest between different‐aged forest stands for bats (or their insect prey), causing an accumulation of bat activity along the edge. Alternatively, edges may be a linear landscape feature similar to roads and riparian corridors that bats use as flight conduits as they move from one place to another. Using ultrasound microphone arrays and recording equipment, we were able to determine flight patterns of bats at hard edges within a landscape of intensively managed loblolly pine (Pinus taeda) plantation in eastern North Carolina, USA, during 2009. Across edges and species sampled, bats consistently flew parallel to edges, suggesting that edges act as conduits for bats. Feeding rates of bats at edges were low, further supporting use of edges as conduits for bats that are either flying along edges to move to and from roosting and foraging habitat patches or moving among foraging patches. Continuous edges should be maintained between linear and nonlinear landscape features, especially where known roosting and foraging areas are being connected by an edge. © 2013 The Wildlife Society.

Bat community response to intensification of biomass production for bioenergy across the southeastern United States

“…All bat species examined were found to have higher estimated occurrence rates at edges compared with interiors. This result aligns with previous research showing that bats appear to preferentially use forest edges for both commuting and foraging (Grindal and Brigham 1999, Hein et al 2009 a , Morris et al 2010, Kalcounis‐Rueppell et al 2013). Mechanistically, this may be due to forest edges acting as windbreaks that foster high densities of flying insects (Lewis 1970, Pasek 1988), or due to edges functioning as landmarks used by bats for orientation while commuting (Verboom and Spoelstra 1999, Kalcounis‐Rueppell et al 2013).…”

“…This result aligns with previous research showing that bats appear to preferentially use forest edges for both commuting and foraging (Grindal and Brigham 1999, Hein et al 2009 a , Morris et al 2010, Kalcounis‐Rueppell et al 2013). Mechanistically, this may be due to forest edges acting as windbreaks that foster high densities of flying insects (Lewis 1970, Pasek 1988), or due to edges functioning as landmarks used by bats for orientation while commuting (Verboom and Spoelstra 1999, Kalcounis‐Rueppell et al 2013). Higher bat activity has been previously documented along edges of loblolly pine stands than forest interiors for nearly all the bat species we investigated: big brown, eastern red, hoary, Seminole, little brown, evening, tri‐colored, and Brazilian free‐tailed bats in North Carolina and South Carolina (Hein et al 2009 a , Morris et al 2010).…”

Variation in regional and landscape effects on occupancy of temperate bats in the southeastern U.S.

“…We hypothesized that the effects of land cover types and forest fragmentation on probability of occupancy varied among species, based on species summer roosting and foraging site preferences [ 11 , 16 , 26 , 45 , 46 ] ( Table 1 ). We calculated percent land coverage within each cell from the National Land Cover Database (NLCD 2011) [ 47 ] and aggregated “Pasture/Hay” and “Cultivated Crops” as Ag, all classes of development as Dev, upland forest types as Forest, and “Woody Wetlands” for bottomland forest (F.Wet).…”

Roads and wildlife: the need for evidence-based decisions; New Zealand bats as a case study

“…North American aerial hawking species were much more active along managed pine plantation edges than in forest interiors, while gleaning, clutter-adapted Myotis species avoided edges (Morris et al 2010). In a related study, bats were recorded as flying predominantly parallel to the forest edge, with few feeding 'buzzes' recorded, suggesting that the edges were being used as linear landscape elements to facilitate commuting (Kalcounis-Rueppell et al 2013). In contrast, Jantzen and Fenton (2013) found edge use to be similar across bats of all foraging types, although the most clutter-adapted species of those studied had significantly lower levels of activity outside of the forest than species classified as 'edge' or 'open' foragers.…”