Climatic and Resource Determinants of Forest Elephant Movements

Beirne, Christopher; Meier, Amelia; Brumagin, Gabriela; Jasperse-Sjolander, Liam; Lewis, Martin W.; Masseloux, Juliana; Myers, Kimberly D.; Fay, Mike; Okouyi, Joseph; White, Lee; Poulsen, John R.

doi:10.3389/fevo.2020.00096

Cited by 20 publications

(20 citation statements)

References 70 publications

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“…NDVI also does not capture the availability of ripe fruit, a key factor mediating forest elephant movement behavior 60 , which may explain why home ranges appear to increase as NDVI increases at the monthly scale. Thus, adapting approaches which facilitate fine temporal and spatial-scale fruit availability, through the use of drones 61 or intensive in-the-field follows 60 , may improve the explanatory power of resource availability in movement models.…”

Section: Discussionmentioning

confidence: 99%

African forest elephant movements depend on time scale and individual behavior

Beirne

Houslay

Morkel³

et al. 2021

Sci Rep

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The critically endangered African forest elephant (Loxodonta cyclotis) plays a vital role in maintaining the structure and composition of Afrotropical forests, but basic information is lacking regarding the drivers of elephant movement and behavior at landscape scales. We use GPS location data from 96 individuals throughout Gabon to determine how five movement behaviors vary at different scales, how they are influenced by anthropogenic and environmental covariates, and to assess evidence for behavioral syndromes—elephants which share suites of similar movement traits. Elephants show some evidence of behavioral syndromes along an ‘idler’ to ‘explorer’ axis—individuals that move more have larger home ranges and engage in more ‘exploratory’ movements. However, within these groups, forest elephants express remarkable inter-individual variation in movement behaviours. This variation highlights that no two elephants are the same and creates challenges for practitioners aiming to design conservation initiatives.

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Section: Discussionmentioning

confidence: 99%

African forest elephant movements depend on time scale and individual behavior

Beirne

Houslay

Morkel³

et al. 2021

Sci Rep

Self Cite

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“…We recommend future studies continue to employ more sophisticated approaches to estimating dung decay, whether modeled or observed in situ , (Hedges, 2012). Further, we recommend weighting decay times by the abundance of dung on transects for both future field and model‐based decay studies to better account for spatially heterogeneous and temporally dynamic distribution of elephants (Beirne et al., 2020).…”

Section: Discussionmentioning

confidence: 99%

“…1). We followed 28 GPS‐collared elephants (Beirne et al., 2020; Mills et al., 2018) locating and then monitoring fresh (<24 hours) dung. We determined dung age as the difference between the dung discovery time and the time that the elephant had been present at the location.…”

Section: Methodsmentioning

confidence: 99%

“…Wildlife can directly increase decay through consumption and/or trampling of dung piles; we quantified animal disturbance as the proportion of all revisits when new animal sign (including disturbance by insects) was observed. We calculated the average number of seeds (>1‐cm) per dung for each month from diet assessments conducted on every third dung encountered (not monitored for decay rate) during elephant focal follows (see Beirne et al., 2020). Higher seed content and less fibrous material is purported to increase the rate of dung decay.…”

Section: Methodsmentioning

confidence: 99%

“…1) and retained cumulative precipitation for the month of deposition and the following month as the measure of precipitation in the combined model. In addition to assessing data for all of Gabon, we hypothesized that country and season would affect dung decay and therefore, tested data partitioned by country and season (see Beirne et al., 2020).…”

Section: Methodsmentioning

confidence: 99%

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Improving population estimates of difficult‐to‐observe species: A dung decay model for forest elephants with remotely sensed imagery

Meier

Shirley

Beirne

et al. 2021

Animal Conservation

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Accurate and ecologically relevant wildlife population estimates are critical for species management. One of the most common survey methods for forest mammals – line transects for animal sign with distance sampling – has assumptions regarding conversion factors that, if violated, can induce substantial bias in abundance estimates. Specifically, for sign (e.g. nests, dung) surveys, a single number representing total time for decay is used as a multiplier to convert estimated sign density into animal density. This multiplier is likely inaccurate if not derived from a study reflecting the spatiotemporal variation in decay times. Using dung decay observations from three protected areas in Gabon, and a previous study in Nouabalé‐Ndoki National Park (Congo), we developed Weibull survival models to adaptively predict forest elephant (Loxodonta cyclotis) dung decay based on environmental variables from field collected and remotely sensed data. Seasonal decay models based on remotely sensed covariates explained 86% of the variation for the wet season and 79% for the dry season. These models included canopy cover, cloud cover, humidity, vegetation complexity and slope as factors influencing dung decay. With these models, we assessed sensitivity of elephant density estimates to spatiotemporal environmental heterogeneity, showing that our methods work best for large‐scale studies >50 km2. We simulated decay studies with and without these variables in four Gabonese national parks and reanalyzed two previous surveys of elephants in Minkébé National Park, Gabon. Disregarding spatial and temporal variation in decay rate biased population estimates up to 1.6 and 6.9 times. Our reassessment of surveys in Minkébé National Park showed an expected loss of 78% of forest elephants over ten years, but the elephant abundance was 222% higher than previously estimated. Our models incorporate field or remotely sensed variables to provide an ecological context essential for accurate population estimates while reducing need for expensive decay field studies.

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Diet DNA reveals novel African Forest elephant ecology on the grasslands of the Congo Basin

Meyer

Honig²,

Hadly

2022

Environmental DNA

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Elephants are essential ecological engineers, creating and maintaining landscape structure and ecosystem function. The recently distinguished and critically endangered forest elephant is currently classified as a selective, non‐destructive frugivorous browser that maintains forest diversity, while the savanna elephant is a mixed feeder, often pushing over trees while maintaining grasslands. The presence and diets of forest elephants on grasslands and the potential maintenance of these systems remain largely unexplored. In the ecotone between the Guinea‐Congolian forest and Sudanian‐Guinean savanna ecosystems in Garamba National Park, DRC, we investigated forest elephant diet selection as a function of sex, age, and habitat using diet DNA (dDNA) metabarcoding of non‐invasively collected dung. GPS collar data were used to determine annual habitat use. Dietary niche partitioning was assessed among megaherbivores in the grasslands. Fecal samples represented the diet of individuals within each habitat, providing valuable insight into the plant biodiversity. Ecological patterns of diet were also revealed using a taxonomically free exact sequence variance approach, highlighting useability in a poorly characterized region. In the early wet season, these typically frugivorous forest elephants were consuming mostly grasses in both the woodland and grassland habitats and showing no sexual dimorphism in diet selection when in the same habitats. However, males were greater risk‐takers, entering the human‐altered landscape to forage on fruit. The forest elephants play a distinctive role within this tropical grassland when compared to other megaherbivores and utilize the unique ecosystem throughout the year. This elephant population is exhibiting behavioral plasticity and shifting their gardening efforts to a novel resource in the grasslands as opposed to their standard role in the forests, which is key to understanding their impact as ecosystem drivers within this landscape. This shift in behavior may result in this recovering elephant population playing a functional role in the restoration and maintenance of these grasslands.

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Climatic and Resource Determinants of Forest Elephant Movements

Cited by 20 publications

References 70 publications

African forest elephant movements depend on time scale and individual behavior

African forest elephant movements depend on time scale and individual behavior

Improving population estimates of difficult‐to‐observe species: A dung decay model for forest elephants with remotely sensed imagery

Diet DNA reveals novel African Forest elephant ecology on the grasslands of the Congo Basin

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