Bridging the gap: assessing the effectiveness of rope bridges for wildlife in Singapore

Abstract

Roads that dissect natural habitats present risks to wildlife, creating gaps or barriers which animals have to traverse in order to move within and between their habitats. Restoring habitat connectivity can be achieved naturally by planting trees and vines to reconnect forest gaps, or artificially by creating culverts for small ground vertebrates, building overpasses for large terrestrial animals, or installing canopy bridges for arboreal fauna. The 3-km Old Upper Thomson Road borders the eastern side of the Central Catchment Nature Reserve, the largest nature reserve in Singapore, and isolates it from neighbouring forest patches. To facilitate safe crossing for tree-dwelling animals such as the critically endangered Raffles’ banded langurs (Presbytis femoralis) along Old Upper Thomson Road, two rope bridges were installed. We monitored the use of these rope bridges by vertebrates from April 2020 to August 2021 through surveillance cameras attached on one end of each bridge. A total of 64 118 videos were processed, with 6218 (9.70%) containing vertebrates. Seven species, including three primates, two squirrels and two reptiles, utilised the bridges to travel between the forests. In particular, Raffles’ banded langurs made a total of 293 successful crossings. We have shown that these rope bridges are useful for arboreal species and can complement national efforts to restore connectivity in fragmented habitats.

An effect of canopy bridges on monkey‐vehicle collision hotspots: Spatial and spatiotemporal analyses

“…Canopy bridge studies often present bridge crossing frequency to evaluate bridge effectiveness in mitigating vehicle collisions (Flatt et al, 2022; Ow et al, 2022; Saralamba et al, 2022). However, bridge use does not directly measure their effectiveness in reducing collisions (van der Grift et al, 2013).…”

“…Several studies (Flatt et al, 2022; Hidalgo‐Mihart et al, 2022) describe similar criteria as ourselves, while others installed bridges in locations where primates cross the road (Buss et al, 2022; Rojas & Gregory, 2022; Teixeira et al, 2013; Valladares‐Padua & Cullen, 1995). Some ensured that primates were present in the surrounding area, and that landowners were willing to have bridges on their properties (Narváez Rivera & Lindshield, 2016; Valladares‐Padua & Cullen, 1995), and several publications stated that the main criterion was a collision hotspot (Lokschin et al, 2007; Maria et al, 2022; Monticelli et al, 2022; Ow et al, 2022; Teixeira et al, 2013).…”

“…In attempts to reduce this impact, artificial canopy bridges are used to encourage primates to cross roads aerially. There is an increasing number of publications describing bridge installation in primate range countries for this purpose (Buss et al, 2022; Corrêa et al, 2018; Flatt et al, 2022; Hidalgo‐Mihart et al, 2022; Linden et al, 2020; Lindshield, 2016; Lokschin et al, 2007; Maria et al, 2022; Monticelli et al, 2022; Ow et al, 2022; Teixeira et al, 2013; Valladares‐Padua & Cullen, 1995).…”

Habitat Use, Terrestriality and Feeding Behaviour of Javan Slow Lorises in Urban Areas of a Multi-Use Landscape in Indonesia

“…A number of these implementations have had long-term monitoring that confirm the ongoing use of the bridges by numerous wildlife [44,45]. In relation to arboreal animals, several species in Singapore were documented as making successful crossings through the use of an artificial rope bridge to travel between forested areas intersected by roads [46]. Further artificial bridges were also proven to be effective in the UK for the hazel dormouse (Muscardinus avellanarius), which is an arboreal species that has been in decline due to the development of human infrastructure such as roads and railways [47].…”