Disentangling controls on animal abundance: Prey availability, thermal habitat, and microhabitat structure

Emma Higgins, Doreen S. Boyd, Tom W. Brown, Sarah C. Owen, Adam C. Algar

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The question of what controls animal abundance has always been fundamental to ecology, but given rapid environmental change, understanding the drivers and mechanisms governing abundance is more important than ever. Here, we determine how multidimensional environments and niches interact to determine population abundance along a tropical habitat gradient. Focusing on the endemic lizard Anolis bicaorum on the island of Utila (Honduras), we evaluate direct and indirect effects of three interacting niche axes on abundance: thermal habitat quality, structural habitat quality, and prey availability. We measured A. bicaorum abundance across a series of thirteen plots and used N-mixture models and path analysis to disentangle direct and indirect effects of these factors. Results showed that thermal habitat quality and prey biomass both had positive direct effects on anole abundance. However, thermal habitat quality also influenced prey biomass, leading to a strong indirect effect on abundance. Thermal habitat quality was primarily a function of canopy density, measured as leaf area index (LAI). Despite having little direct effect on abundance, LAI had a strong overall effect mediated by thermal quality and prey biomass. Our results demonstrate the role of multidimensional environments and niche interactions in determining animal abundance and highlight the need to consider interactions between thermal niches and trophic interactions to understand variation in abundance, rather than focusing solely on changes in the physical environment.

Original languageEnglish
Article number7930
Pages (from-to)11414-11424
Number of pages11
JournalEcology and Evolution
Issue number16
Early online date24 Jul 2021
Publication statusPublished - 16 Aug 2021
Externally publishedYes


  • abundance
  • Anolis
  • habitat structure
  • microhabitat
  • population size
  • prey availability
  • thermal ecology
  • tropical forests


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