Stretching the Habitat Envelope: Insectivorous Bat Guilds Can Use Rubber Plantations, but Need Understorey Vegetation and Forest Buffers

Kadambari Deshpande,Jagdish Krishnaswamy,Mahesh Sankaran,Nachiket Kelkar

doi:10.3389/fcosc.2021.751694

Abstract

Effects of land-cover change on insectivorous bat activity can be negative, neutral or positive, depending on foraging strategies of bats. In tropical agroforestry systems with high bat diversity, these effects can be complex to assess. We investigated foraging habitat use by three insectivorous bat guilds in forests and rubber plantations in the southern Western Ghats of India. Specifically, we monitored acoustic activity of bats in relation to (1) land-cover types and vegetation structure, and (2) plantation management practices. We hypothesized that activity of open-space aerial (OSA) and edge-space aerial (ESA) bat guilds would not differ; but narrow-space, flutter-detecting (NSFD) bat guild activity would be higher, in structurally heterogeneous forest habitats than monoculture rubber plantations. We found that bat activity of all guilds was highest in areas with high forest cover and lowest in rubber plantations. Higher bat activity was associated with understorey vegetation in forests and plantations, which was expected for NSFD bats, but was a surprise finding for OSA and ESA bats. Within land-cover types, open areas and edge-habitats had higher OSA and ESA activity respectively, while NSFD bats completely avoided open habitats. In terms of management practices, intensively managed rubber plantations with regular removal of understorey vegetation had the lowest bat activity for all guilds. Intensive management can undermine potential ecosystem services of insectivorous bats (e.g., insect pest-control in rubber plantations and surrounding agro-ecosystems), and magnify threats to bats from human disturbances. Low-intensity management and maintenance of forest buffers around plantations can enable persistence of insectivorous bats in tropical forest-plantation landscapes.

Highlights

Tropical forest fragmentation caused by agricultural intensification and expansion of commercial agroforestry plantations is a significant threat to biodiversity (Saunders et al, 1991; Raman, 2006; Gardner et al, 2009; Kumar et al, 2010; Canale et al, 2012)
Average open-space aerial (OSA) bat activity was highest in settlements and teak plantations (14 and 9.4 passes/h), followed by forests and rubber plantations (4.28 and 2.54 passes/h; Table 3)
Activity of all bat guilds was positively correlated with percent forest cover and negatively with percent

Summary

Introduction

Tropical forest fragmentation caused by agricultural intensification and expansion of commercial agroforestry plantations is a significant threat to biodiversity (Saunders et al, 1991; Raman, 2006; Gardner et al, 2009; Kumar et al, 2010; Canale et al, 2012). Responses may vary by the type of biome (temperate/tropical: Erickson and West, 2003; Heer et al, 2015), degree and nature of land conversion and agricultural intensification (Gorresen and Willig, 2004; Frey-Ehrenbold et al, 2013), sampling scale (local to landscape: Erickson and West, 2003; Gehrt and Chelsvig, 2003; Meyer et al, 2008), and regional species diversity and trait distributions (Duchamp and Swihart, 2008; Meyer et al, 2008; Ducci et al, 2015)

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Results

Conclusion