Life in the Canopy: Using Camera-Traps to Inventory Arboreal Rainforest Mammals in Borneo

Abstract

Arboreal mammals form a diverse group providing ecologically important functions such as predation, pollination and seed dispersal. However, their cryptic and elusive nature, and the heights at which they live, makes studying these species challenging. Consequently, our knowledge of rainforest mammals is heavily biased towards terrestrial species, limiting our understanding of overall community structure and the possible impacts of human-induced disturbance. We undertook the first in-depth appraisal of an arboreal mammal community in Southeast Asia, using camera-traps set in unlogged and logged tropical rainforest in Sabah, Borneo. Using paired canopy and terrestrial camera-traps at 50 locations (25 in unlogged forest, 25 in logged), we assessed the effectiveness of camera-trapping at characterising the arboreal versus terrestrial community, and tested the influence of strata and forest type on community structure and composition. The paired design detected 55 mammal species across 15,817 camera-trap nights (CTNs), and additional canopy sampling in a subset of trees added a further two arboreal species to the inventory. In total, thirty species were detected exclusively by terrestrial camera-traps, eighteen exclusively by canopy camera-traps, and nine by units set at both heights, demonstrating significant differences between arboreal and terrestrial communities. This pattern was strongest in unlogged forest, reflecting greater structural diversity of this habitat, but held in logged forest as well. Species accumulation curves revealed that canopy camera-trapping significantly boosted species inventories compared to terrestrial-only sampling, and was particularly effective at detecting gliding mammals, rodents and primates. Canopy inventories took longer to reach an asymptote, suggesting that a greater sampling effort is required when deploying canopy camera-traps compared to those set on the ground. We demonstrate that arboreal mammals in Borneo’s rainforest form a diverse and distinct community, and can be sampled effectively using canopy camera-traps. However, the additional costs incurred by sampling in the canopy can be substantial. We provide recommendations to maximise sampling effectiveness, while bringing down costs, to help encourage further study into one of the last frontiers of tropical forest research.

Estimating animal density for a community of species using information obtained only from camera‐traps

“…Given the importance of understanding activity levels, further studies would be helpful to test assumptions, for example using arboreal camera‐traps (e.g. Haysom et al, 2021).…”

Monitoring for the presence of invasive arboreal rodents: an assessment of monitoring tools across forest strata

“…Our data suggest that the optimal period of deployment may vary among methods; chew cards and tracking tunnels can quickly reach saturation at high rodent densities, whereas camera traps are only limited by battery life and data storage. We observed chew mark and footprint saturation at multiple sites, which could be attributed to both high site-level rodent activity as well as the length of the deployment period ( Ideally, mixed-method monitoring designs would implement shorter deployment periods for lure-based methods, and longer deployment periods for camera traps or similar methods (Haysom et al 2021). Such a design would be ecologically robust, while also reducing logistical complexity: the simplest device to deploy and retrieve requires shorter deployment periods, and the more technically challenging device requires longer periods.…”

How do terrestrial wildlife communities respond to small‐scale Acacia plantations embedded in harvested tropical forest?

“…Further, our study focuses on medium to large terrestrial species, a group that is frequently studied to assess the impacts of forest disturbance (Maiwald et al, 2020 ; McShea et al, 2009 ; Ng et al, 2021 ). Many other taxa, however, experience biodiversity loss within production landscapes including arboreal species (Haysom et al, 2021 ), birds (Beukema et al, 2007 ; Peh et al, 2006 ; Styring et al, 2011 ; Waltert et al, 2004 ), and amphibians (Asad et al, 2020 ; Wanger et al, 2010 ). It is possible that other communities of wildlife are more affected by LPF than the highly mobile medium‐to‐large terrestrial species.…”