Echolocation and roosting ecology determine sensitivity of forest‐dependent bats to coffee agriculture

Abstract

Species differ in vulnerability to anthropogenic land use changes. Knowledge of the mechanisms driving differential sensitivity can inform conservation strategies but is generally lacking for species-rich taxa in the tropics. The diverse bat fauna of Southeast Asia is threatened by rapid loss of forest and expanding agricultural activities, but the associations between species, traits, vulnerability to agriculture, and the underlying drivers have yet to be elucidated. We studied the responses of speciose insectivorous bat assemblages to robusta coffee cultivation in Sumatra, Indonesia.We compared abundance, species richness, and assemblage structures of bats between forests and coffee farms based on trapping data and evaluated the influence of vegetation complexity on assemblage composition and species-level reactions.Bat abundance and species richness were significantly lower in coffee farms than in forests. Bat assemblage structure differed between land uses, and the overall variation can be largely explained by vegetation simplification. Species sensitive to coffee agriculture were associated with more complex vegetation structure, whereas tolerant species were associated with simpler vegetation structure. Sensitive and tolerant species differed in the type, frequency, and bandwidth of echolocation calls and roost use. Species sensitive to coffee use broadband and high-pitched frequencymodulated calls, which are efficient at detecting insects in complex vegetation, and roost in plant structures that may be lost as vegetation is simplified. In contrast, tolerant species used lower pitched constant-frequency calls and roost in caves. We advocate for greater use of trait analyses in studies seeking to clarify the influence of agriculture on diverse tropical bat faunas.Abstract in Indonesian is available with online material. K E Y W O R D Sforest bat, Indonesia, land use change, species vulnerability, trait-based analyses, vegetation simplification

Intact forests of the Hkakabo Razi Landscape are a hotspot of bat diversity in South-east Asia

“…Forest-interior specialist bats are a priority for chiropteran conservation, being most at risk from habitat change. They have strong site fidelity, are less geographically mobile than nomadic generalist bats such as Cynopterus sphinx , and have smaller home ranges that do not extend beyond forest boundaries (Struebig et al, 2008; Huang et al, 2019). Compared to cave-roosting bats, they are more susceptible to microclimate and habitat changes and more vulnerable to loss of roosting sites, which include hollows and cavities of standing and fallen trees (Struebig et al, 2008).…”

Bat point counts: a novel bat sampling method shines light on flying bat communities

“…KD, EY). Thus, it appears that much of the bat assemblage is ignored when using only mist nets, underlining their strong taxonomic bias in our system (Huang et al, 2019), and suggesting similar biases in other tropical studies might exist. As a consequence, the contribution of bat communities to regulating insect populations in oil palm may also have been underestimated.…”

Bat Ensembles Differ in Response to Use Zones in a Tropical Biosphere Reserve

“…The decrease in forest-interior species within the transition and extralimital agriculture indicates a negative response to land-use change for this ensemble. Vegetation simplification is a consequence of agricultural intensification [67,68] and ecomorphological traits characteristic of forest-dependent species [23] are a limitation to forest ensembles persisting in these simplified, open spaces. Mechanisms for this decline in bats include reduced roost availability for plant-roosting species [67,69,70], degraded roost quality [71], and reduced foraging success.…”

“…Foliage roosting species are affected by a reduction in roosting opportunities whereas cave-dwelling species are affected by both disturbance at the roost and greater commuter costs as foraging habitats are fragmented [38,82]. Body mass is positively correlated with resilience to disturbance, whereas smaller species that emit higher peak frequencies responded negatively [67,83]. Mean body mass of the species recorded in our study was twice as high in the extralimital agriculture (26.44 g) than in the core zone (13.11 g; Table 2), however this does not consider the relative abundance of each species.…”