Accurate and precise population estimates form the basis of conservation action but are lacking for many arboreal species due to the high costs and difficulty in surveying these species. Recently, researchers have started to use drones to obtain data on animal distribution and density. In this study, we compared ground and drone counts for spider monkeys (Ateles geoffroyi) at their sleeping sites using a custom-built drone fitted with a thermal infrared (TIR) camera. We demonstrated that a drone with a TIR camera can be successfully employed to determine the presence and count the number of spider monkeys in a forested area. Using a concordance analysis, we found high agreement between ground and drone counts for small monkey subgroups (<10 individuals), indicating that the methods do not differ when surveying small subgroups. However, we found low agreement between methods for larger subgroups (>10 individuals), with drone counts being higher than the corresponding ground counts in 83% of surveys. We could identify additional individuals from TIR drone footage due to a greater area covered compared to ground surveys. We recommend using TIR drones for surveys of spider monkey sleeping sites and discuss current challenges to implementation.

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Deforestation impacts canopy connectivity when landscapes are fragmented due to roads and other types of linear infrastructure. Natural canopy bridges become vital to arboreal animals, especially for animals that are reluctant to use the ground. When canopy regrowth cannot occur, artificial canopy bridges have been implemented to mitigate the consequences of linear infrastructure. The aim of our study was to evaluate the evidence for the use of artificial canopy bridges by spider monkeys (Ateles spp.) to cross linear infrastructure that interrupts canopy connectivity. We report details of five cases in which the absence of evidence for spider monkeys using artificial canopy bridges to cross linear infrastructure was based on systematic monitoring. We examined the factors that may constrain spider monkeys to use artificial faunal overpasses and made recommendations for effective artificial faunal overpasses for spider monkeys.

Detecting spider monkeys from the sky using a high-definition RGB camera: a rapid-assessment survey method? http://researchonline.ljmu.ac.uk/id/eprint/15857/ Article LJMU has developed LJMU Research Online for users to access the research output of the University more effectively.