Dung beetle-mammal dung interaction networks are resilient across a gradient of forest disturbance

This blog post is provided by Li Yuen Chiew and Eleanor M. Slade and tells the #StoryBehindThePaper for the paper “Tropical forest dung beetle-mammal dung interaction networks remain similar across an environmental disturbance gradient”, which was recently published in the Journal of Animal Ecology.
Li Yuen Chiew: I am a conservation ecologist, whose research focuses on biodiversity conservation and ecosystem ecology, with a particular interest in invertebrates. My PhD research focused on the resilience of tropical rainforests to human disturbance and conversion to plantations and I looked at how interaction networks and ecosystem functioning changed across an environmental disturbance gradient.

Dung beetle assemblages are influenced by different land-uses, where forest conversion to cultivated grassland or plantations changes dung beetle species composition and reduces species richness and biomass compared to undisturbed forest. Dung beetle communities in primary forest are thought to be more diverse since primary forests generally support a greater diversity of mammal species, particularly larger mammals. Therefore, dung beetles are recognized as a good indicator taxa of the health of mammal communities and there have been several recent studies unravelling the interactions between dung beetles and the mammal dung on which they feed.

Catharsius sp. dung beetles feeding on dung in a tropical forest in Sabah, Malaysia (Photo credit: Nichar Gregory)

Human dung is usually used as a bait for dung beetle trapping in the tropics, since it attracts a wide range of dung beetle species, and can therefore be used as a standardized bait type to compare dung beetle communities across sites. However, to document the species-specific interactions between dung beetles and mammals and to explicitly test the specificity of dung beetle interactions within broad groups of mammals (e.g. carnivores, omnivores, herbivores, frugivores) a more complex experimental design is needed.

Collecting dung beetles from the pitfall trap after 48 hours (Photo credit: South East Asia Rainforest Research Partnership (SEARRP)).

The study was conducted between February to April 2018, and 9,236 individuals of 50 species of dung beetles were collected from 96 dung-baited pitfall traps using eight mammal dung types, baited with realistic dung sizes. This study presented the first records of dung beetle-mammal dung feeding networks for Borneo, allowing us to discover how forest disturbance and changes in mammal communities affect dung beetle communities .

Interestingly, dung beetle-mammal dung interaction networks in the tropical rainforests of Borneo remained structurally similar to forests that had been moderately disturbed by logging, only becoming simplified in the highly disturbed forests and plantations. Mammal diversity changed little across the gradient, and a reduction in dung beetle species richness in the most disturbed sites, was therefore likely driven by habitat changes, such as reduced canopy cover, and increased temperatures. Reduced numbers of species of beetles in the plantations then resulted in fewer dung beetle-mammal dung interactions and simplified networks. Our study also confirms the generalist feeding patterns of dung beetles, which makes them robust to changes in mammal community composition which often accompany forest disturbance. However, although dung beetles are usually considered to be generalists, we found that they do have preferences, and certain dung types are more commonly utilized than others, with pig and orang utan being the most preferred while sun bear and civet dung were the least preferred. Overall, our results suggest that even disturbed, fragmented and previously logged forests can retain structurally similar assemblages and interactions to primary forests. However, we caution, that severely disturbed forests and those converted to plantations, show marked changes in network structure, with a loss of both species and interactions, with potential consequences for the functioning of the ecosystem.

Read the paper

Read the full paper here: Chiew, L. Y., Hackett, T. D., Brodie, J. F., Teoh, S. W., Burslem, D. F. R. P., Reynolds, G., Deere, N. J., Vairappan, C. S., & Slade, E. M. (2022). Tropical forest dung beetle–mammal dung interaction networks remain similar across an environmental disturbance gradient. Journal of Animal Ecology, 00, 1– 14. https://doi.org/10.1111/1365-2656.13655

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