Abstract
As a keystone megafaunal species, African forest elephants (Loxodonta cyclotis) influence the structure and composition of tropical forests. Determining the links between food resources, environmental conditions and elephant movement behavior is crucial to understanding their habitat requirements and their effects on the ecosystem, particularly in the face of poaching and global change. We investigate whether fruit abundance or climate most strongly influence forest elephant movement behavior at the landscape scale in Gabon. Trained teams of ‘elephant trackers’ performed daily fruit availability and dietary composition surveys over a year within two relatively pristine and intact protected areas. With data from 100 in-depth field follows of 28 satellite-collared elephants and remotely sensed environmental layers, we use linear mixed-effects models to assess the effects of sites, seasons, individual identification, elephant diet, and fruit availability on elephant movement behavior at monthly and three-day time scales. At the month-level, rainfall, and to a lesser extent fruit availability, most strongly predicted the proportion of time elephants spent in long, directionally persistent movements. Thus, even elephants in moist tropical rainforests show seasonal behavioral phenotypes linked to rainfall. At the follow-level (2-4 day intervals), relative support for both rainfall and fruit availability decreased markedly, suggesting that at finer spatial scales forest elephants make foraging decisions largely based on other factors not directly assessed here. Individual identity explained the majority of the variance in the data, and there was strong support for interindividual variation in behavioral responses to rainfall. Taken together, this highlights the importance of approaches which follow individuals through space and time. The links between climate, resource availability and movement behavior provide important insights into the behavioral ecology of forest elephants that can contribute to understanding their role as seed dispersers, improving management of populations, and informing development of solutions to human-elephant conflict.
Highlights
Understanding the environmental factors that influence animal movements is fundamental to theoretical and applied research in the field of movement ecology (Nathan et al, 2008)
To investigate the ecological and environmental drivers influencing elephant movement behavior, we employed a four step approach: Step 1 – we assessed the degree of spatiotemporal variation in availability and diversity of elephant consumed fruits; Step 2 – we explored how fruit availability influenced forest elephant diet; Step 3 – we determined how fruit availability and climate factors affected variation in elephant movement behavior; and Step 4 – we assessed the evidence for individual-level sensitivity to fruit availability and climatic covariates
To determine the relative importance of fruit availability and/or climate factors on movement behavior, we examined how the monthly ratio of encamped behavior to directed movement varied as a function of site, monthly mean fruit availability, monthly mean precipitation, and monthly mean temperature
Summary
Understanding the environmental factors that influence animal movements is fundamental to theoretical and applied research in the field of movement ecology (Nathan et al, 2008). The African forest elephant (Loxodonta cyclotis) is a wideranging megaherbivore and keystone species for Afrotropical rainforests that influences the composition and structure of the ecosystem through movement and browsing (Turkalo and Fay, 2001; Blake, 2002; Poulsen et al, 2018; Cardoso et al, 2019). The ranging behavior of forest elephants has been linked to resources such as browse abundance, mineral deposits, water resources, and the physical and seasonal distribution of ripe fruit (Blake, 2002; Blake et al, 2006; Buij et al, 2007; Mills et al, 2018), but the relative importance of these resources on their movements is largely unknown
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