Changes in trophic ecology of mobile predators in response to rainforest degradation

Journal article

1. Accelerating loss and degradation of tropical forests has led to a pressing needto understand the conservation value of remaining forests. Whereas most stud-ies focus on the responses in community composition and taxonomic richness,more sensitive responses to habitat degradation are likely to be apparent throughchanges in the trophic complexity of generalist predators. Food web theory pre-dicts that both trophic position and niche breadth of predators decrease withhabitat degradation, with consequences for biotic interactions and ecosystemfunctioning.
2. Using a stable isotope approach, we analysed trophic positions and niche breathsof an important guild of top predators: insectivorous bats, in the tropical forestsof Sabah, Borneo. We aimed to determine the responses in their trophic ecologyacross an experimental gradient of forest degradation at different spatial scales.
3. At the landscape scale, trophic niche breadth contracted substantially (78%) inassociation with a narrow reduction (26%) in forest cover. However, food chainswere longer in ecosystems with lower tree canopies, representative of localisedhabitat simplification. Marked differences in trophic niche breath of and trophicposition between echolocation guilds provided further evidence for inter- guildniche partitioning within bat assemblages. Overall, the functionally importantshifts in trophic pathways discriminated among habitats of varying degrees ofdegradation more reliably than conventional community descriptors, such as di-versity metrics.
4. Synthesis and applications. This study reveals that habitat quality thresholds—below which we see substantial changes to trophic complexity—are higher thanpreviously considered. Our analysis suggests that patches of forest with coverabove 90% should be prioritised for conservation over more highly degradedecosystems. As these effects were detected after approximately 30 years post-logging, they likely reflect relatively long-term responses to forest degradation.

Authors: Kemp, VA; Grey, J; Hemprich‐Bennett, D; Rossiter, SJ; Lewis, OT

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Wiley
• Journal: Journal of Applied Ecology
• Volume: 60
• Issue: 6
• Pages: 1139-1148
• Publication date: 2023-03-21
• Acceptance date: 2023-03-04
• DOI: 10.1111/1365-2664.14396
• EISSN: 1365-2664
• ISSN: 0021-8901
• Language: English
• Keywords: bats; diet breath; logging; predator–prey interactions; spatial scale; stable isotopes; trophicposition; tropical rainforest