Natural canopy bridges effectively mitigate tropical forest fragmentation for arboreal mammals

Tremaine Gregory,Jessica L Deichmann,Joseph Kolowski,Farah Carrasco-Rueda,Alfonso Alonso

doi:10.1038/s41598-017-04112-x

Tremaine Gregory, Jessica L Deichmann + Show 3 more

Open Access

https://doi.org/10.1038/s41598-017-04112-x

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Abstract

Linear infrastructure development and resulting habitat fragmentation are expanding in Neotropical forests, and arboreal mammals may be disproportionately impacted by these linear habitat clearings. Maintaining canopy connectivity through preservation of connecting branches (i.e. natural canopy bridges) may help mitigate that impact. Using camera traps, we evaluated crossing rates of a pipeline right-of-way in a control area with no bridges and in a test area where 13 bridges were left by the pipeline construction company. Monitoring all canopy crossing points for a year (7,102 canopy camera nights), we confirmed bridge use by 25 mammal species from 12 families. With bridge use beginning immediately after exposure and increasing over time, use rates were over two orders of magnitude higher than on the ground. We also found a positive relationship between a bridge’s use rate and the number of species that used it, suggesting well-used bridges benefit multiple species. Data suggest bridge use may be related to a combination of bridge branch connectivity, multiple connections, connectivity to adjacent forest, and foliage cover. Given the high use rate and minimal cost, we recommend all linear infrastructure projects in forests with arboreal mammal populations include canopy bridges.

Highlights

Linear infrastructure, such as pipelines, roads, railways, and transmission lines, has the potential to impact wildlife in many ways, most notably reducing access to resources and increasing mortality[1,2,3]
Primate groups were observed crossing at the canopy level over the proposed RoW at a rate of 2.7 (25 crossings) and 3.6 (29 crossings) times/10 km walked in the Bridge Zone (BZ) and No Bridge Zone (NBZ), respectively
Of all groups observed during transect walks, 76% and 81% crossed in the BZ and NBZ, respectively

Summary

Introduction

Linear infrastructure, such as pipelines, roads, railways, and transmission lines, has the potential to impact wildlife in many ways, most notably reducing access to resources and increasing mortality[1,2,3]. These impacts can be even more pronounced in tropical forests, due to their extreme physical and ecological complexity[4]. Reducing the impacts of some forms of linear infrastructure like roads, transmission lines, and railways on arboreal wildlife is challenging for various reasons[4] These forms of infrastructure represent a long-term source of forest fragmentation. It is necessary to document the degree to which these bridges are used by various taxa and the extent to which these taxa can and will cross RoW clearings on the ground

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