THE USE OF SINGLE-ROPE BRIDGES BY ARBOREAL MAMMALS IN AN ATLANTIC FOREST HOUSING DEVELOPMENT AREA

Use of single-ropes bridges by arboreal mammals

Abstract

Forest gaps created by urban expansion and infrastructure construction pose a significant challenge to arboreal organisms by isolating habitat patches and increasing mortality. Single-rope bridges can alleviate the impacts of fragmentation by linear infrastructure. In this study, we monitored 15 single-rope bridges installed in an expanding urban area of Mata de São João, Bahia, Brazil. Our primary goal was to investigate their use by arboreal mammals, evaluate the effect of bridge material type, length, and canopy cover, and determine if usage increased over time. Using camera-traps, we recorded eight mammal species using bridges, with six species confirmed to be crossing: Callithrix jacchus, Marmosa sp., Chaetomys subspinosus, Guerlinguetus brasiliensis, Didelphis sp., and Coendou insidiosus. Species recorded but with no crossing confirmed were Rhipdomys mastacalis and Bradypus torquatus. Thick sisal ropes showed a tendency to promote a higher crossing rate compared to nylon rope types. The bridge length and canopy cover were negligible factors. We also found that the time since installation (i.e., the time elapsed since bridge installation, measured by sequential campaigns) tends to reduce the frequency of records, but the frequency of crossings remained unaffected. Our findings reaffirm the functional use of low-cost rope bridges by arboreal mammals while crossing small gaps, and suggest that the success of crossing can be improved by the bridge material. Single-rope bridges offer a high benefit-cost ratio, enabling greater deployment and wider coverage for wildlife crossings. In urban and peri-urban contexts, this low-cost disposal can reduce threats that arboreal mammals face when descending to the ground.