190 B. Galea et al.
We observed individuals of M. fascicularis fascicularis and T. obscurus carbo groups in close proximity at roadsides on nine occasions but observed interaction between the species only once, when three M. fascicularis fascicularis individuals from the same group and one T. obscurus carbo crossed together at Jalan Teluk Datai. Based on the roadkill and observational data recorded,
we recommend both natural and artificial canopy bridges are installed to reduce roadkill rates of arboreal wildlife, especially primates, and to improve habitat connectivity at multiple locations along sections of Jalan Teluk Datai, Jalan Teluk Yu and Jalan Ulu Melaka, and two sections of Jalan Ayer Hangat (Fig. 1). The final selection of proposed canopy bridge sites was based on two factors. Firstly, we considered the rate of roadkill observed. Secondly, we assessed the potential of each site to facilitate the reconnec- tion of major forest fragments and to support the movement of arboreal animals between these areas. In cases where a site had a high rate of roadkill but lacked the capacity to re- connect significant forest fragments (e.g. Jalan Pantai Kok), it was excluded from the proposed canopy bridge network. However, these locations remain under consideration for future inclusion in the network pending the successful piloting of the selected canopy bridge sites. Although there was not a significant forest gap at Jalan Teluk Datai, we included it in the proposed network as the roadkill rate was markedly higher than in other areas. The prioritization of sites that met both the roadkill rate and forest connectiv- ity criteria will ensure that the canopy bridge network max- imizes its potential for reducing wildlife–vehicle collisions whilst supporting the long-term conservation of arboreal species. Macaca fascicularis fascicularis and T. obscurus carbo have both shown a propensity to use artificial canopy bridges (Yap et al., 2022). Slow lorises have also been re- corded successfully crossing such structures (Birot et al., 2020). Appropriate tree species to plant along roadsides as
natural canopy bridges include figs such as the cluster fig (Malay: tangkol) Ficus racemosa or common yellow-stem fig (pokok buah ara) Ficus fistulosa,pacific lychee (kasai daun besar) Pometia pinnata, monkey-pod tree (pokok pukul lima) Albizia saman, Alexandrian laurel (penaga laut) Calophyllum inophyllum and pokok buak-buak Teijsmanniodendron pteropodum, as they are fast-growing and have far-extending crowns and small, light fruits that will not damage vehicles when they fall. The approximate number of saplings required along the roadsides where we recommend wildlife corridors are as follows, based on a re- commended 1.8-m distance between the planted saplings (Kerr & Mackintosh, 2012): Jalan Teluk Datai: 422 saplings (760 m of total roadside); Jalan Teluk Yu: 111 (200 mof total roadside); Jalan Ulu Melaka: 88 (160 m); Jalan Ayer Hangat (1): 255 (230 m); and Jalan Ayer Hangat (2): 444 (800 m).
Artificial canopy bridges can be tied to trees where
feasible (in consultation with a certified arborist) or to 10–15mtall galvanized steel
poles.Aladder or lattice canopy bridge design using low-cost, lightweight and robust materials, such as repurposed firehose (Yap et al., 2022), might prove sufficient for langurs, macaques and slow lorises. For a more permanent bridge, engineered over- passes could be constructed, although this would signifi- cantly increase costs. Engaging local people in a partici- patory approach to contribute to canopy bridge design, construction and monitoring could foster environmen- tal stewardship amongst community members, and build public trust regarding wildlife conservation interventions (Fan & Lindshield, 2022). The artificial canopy bridges would serve as short- to mid-term measures to facilitate canopy connectivity whilst planted tree saplings grow. Following establishment of artificial canopy bridges, we recommend utilizing camera traps to record crossing details (species, age, sex, number of individuals) and to collect behavioural and environmental data during crossing events. Relevant parameters to record include mode of locomotion (e.g. walking, running) and vigilance behaviour on the bridge, time and weather (van der Grift et al., 2015). To ensure the safety of pedestrians and primates, it will be essential to collaborate with experts in bridge design and construction, install clear signage, consider human–primate separation measures, conduct regular inspections and maintenance, engage with the local com- munity to raise awareness, and coordinate with relevant authorities and conservation organizations to achieve compliance with safety regulations and best practices. We also recommend the installation of speed limits, humps and signs along the road sections, to slow down vehicles and inform drivers of the potential threat they pose to wildlife by speeding, to help further reduce roadkill and to increase public awareness regarding the harm that food provisioning causes to primates, especially along roadsides. We will continue working closely with local authorities, including the Kedah State Forestry Department, the Lang- kawi Development Authority, the Langkawi Public Works Department, the Langkawi Research Centre and commu- nity groups to implement our recommendations. We have begun discussions with the relevant authorities, partners and other pertinent parties, focusing on the initiation of construction of the canopy bridge network in 2024. This project could be an exemplar for multi-partner collab- oration to restore and maintain habitat connectivity for arboreal wildlife in other locations.
Author contributions Study design, fieldwork: all authors; data analysis, writing: BG, NR.
Acknowledgements We thank the Kedah State Forestry Department for technical advice and support; the Datai Langkawi
Oryx, 2024, 58(2), 187–191 © The Author(s), 2023. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605323001333
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