The influence of structural clutter on activity patterns of insectivorous bats

Abstract

We experimentally tested the hypothesis that three-dimensional structural clutter is a major factor affecting habitat choice by insectivorous bats. To do this we artificially increased clutter at two sites used by bats without affecting prey availability. Our measure of available insect prey did not differ between treatment and control sites, indicating that only the spatial complexity of the habitat type was manipulated. Artificial clutter negatively affected foraging activity by small bats (Myotis spp.), supporting the hypothesis that physical clutter does affect foraging by bats. In direct contrast to our expectation, large bats (Eptesicus fuscus, Lasiurus cinereus, Lasionycteris noctivagans) were apparently unaffected by the clutter treatment. We suggest that this may be an artifact of our experimental design, because our ultrasonic detectors probably recorded large bats flying above the artificial clutter.

A landscape perspective on bat foraging ecology along rivers: does channel confinement and insect availability influence the response of bats to aquatic resources in riverine landscapes?

“…To control for the effects of environmental clutter (Brigham et al 1997), we positioned the bat detectors so that physical structure (e.g., vegetation) did not block the microphones. Detectors were put into plastic containers to protect them from precipitation, and microphones were oriented at 45°upwards (O'Farrell 1998).…”

“…Lower bat activity along unconfined sites with alder vegetation than confined sites types may be from alder trees interfering with successful prey capture by hindering echolocation and by creating obstacles in the flight path (Brigham et al 1997;Mackey and Barclay 1989). Bats typically prefer areas with low structural clutter in comparison to those with high structural clutter (Brigham et al 1997;Erickson and West 2003;Sleep and Brigham 2003). For example, Loeb and O'Keefe (2006) documented high bat activity in areas with lowdensity vegetation.…”

Synthesis and Comparison of Baseline Avian and Bat Use, Raptor Nesting and Mortality Information from Proposed and Existing Wind Developments: Final Report.

“…Bats have the ability to navigate through constructed clutter zones made of staggered vertical strands of twine 3 mm in diameter spaced 1 m apart (Mackey and Barclay 1989, Brigham et al 1997.…”

Bats (Mammalia, Chiroptera) of an urban park in the metropolitan area of Rio de Janeiro, southeastern Brazil

“…Bats may show fidelity to roosts in hollow trees (e.g., LewiS, 1995), but there are species that periodically change roosts and so need a high availability of them (e.g., yaSui et al, 2004). Hollows are more frequent in trees that undergo pruning or breakage of branches (miLano & daLCin, 2000) or in trees that are old (LewiS, 1995;BriGham et al, 1997;yaSui et al, 2004), such as many trees in our study site and on streets of Rio de Janeiro. In Brazil, mainly Molossidae and Vespertilionidae bats do frequently use roof lining and other structures in residences as roosts in urban areas (Bredt & uieda, 1996;Lima, 2008), but we still need to investigate the availability of hollow trees and their occupancy rates by these bats (yaSui et al, 2004).…”

“…The availability of hollow trees and other roosts is an important factor that should be considered in the analysis of bat occurrence (e.g., humPhrey, 1975;Kunz, 1982;BriGham et al, 1997;JohnSon et al, 2008). Bats may show fidelity to roosts in hollow trees (e.g., LewiS, 1995), but there are species that periodically change roosts and so need a high availability of them (e.g., yaSui et al, 2004).…”