668 R. Horion et al.
TABLE 1(Cont.) Process Covariates
RAI of sympatric spe- cies (i.e. RAI_Leopard, RAI_Lion, RAI_Hyaena, RAI_Wild_dog)
Description
Relative abundance index for each of the sympatric large carnivore
Hypotheses
Interactions between sympatric carnivores affect their site use (Creel et al., 2001)
Predicted sign of influence
(−) Higher local abun- dance of sympatric carni-
vores may increase competition & decrease subordinate species’ site use (Sarmento et al., 2011); (+) higher local abun- dance of sympatric carni- vores may increase scavenging opportunities &/or dominant relation- ships with other carni- vores (Swanson et al., 2014)
Source of the data
This study
power if r.0.6 (Burnham et al., 2002). We followed a two- step procedure to select covariates that best explainedmodel heterogeneity. Firstly, we modelled the influence of four covariates on ρ (effort, presence of leopard, presence of lion and presence of African wild dog) whilst keepingψcon- stant. Then, we modelled the influence of nine covariates on ψ (distance to the Gambian River, distance to the Niokolo River, distance to the nearest river, distance to the nearest road, distance to the edge of the Park and the RAIs of each of the four sympatric large carnivores) whilst keeping detection constant (Strampelli et al., 2022).Weranked mod- els using the Akaike information criterion corrected for small samples (AICc; Burnham et al., 2002), and we con- sidered models with ΔAICc,2 to be equally plausible. Finally, we assessed the goodness of fit of each top model based on Pearson’s χ2 test (MacKenzie & Bailey, 2004). Values of the overdispersion parameter ĉ.1 were inter- preted as overdispersion and ĉ.4 as a lack of fit, with ĉ va- lues near 1 representing models with the best fit (Mazerolle, 2020).
Daily activity patterns We used a kernel density function to analyse timestamp data from independent capture events of each of the four carnivore species (Meredith & Ridout, 2024), to determine the extent of their temporal activity overlap. Non-parametric coefficient of overlap values (Δ4) range from 0 (no overlap) to 1 (uniformly distributed and 100% overlap). We followed previous recommendations (Ridout & Linkie, 2009) for the choice of operators and worked with Δ4 when samples were larger than 50 observa- tions and Δ1 otherwise. We generated 1,000 bootstrap esti- mates for each comparison to extract confidence intervals (Schmid & Schmidt, 2006). We considered the overlap to be low when Δx#0.50, moderate when 0.50,Δx#0.75 and high when 0.75,Δx#1.00 (Monterroso et al., 2014).
Temporal overlap was calculated using the R package overlap (Meredith & Ridout, 2024).
Results
Camera-trap data Six cameras experienced substantial data loss (primarily because of human interference, destruction or softwaremal- function) and thus did not contribute any data. The final da- taset comprised a total of 121,282 images from 11,082 trap-days, of which 26%(n = 31,845) were blank (no species recorded) and 59%(n = 70,991) showed wild mammals (40 species; Supplementary Table 2). The most frequently detected large carnivorewas the spotted hyaena (453 images, of which 278 were independent images), followed by leopard (168 images, 106 independent), lion (165 images, 59 independent) and African wild dog (114 images, 22 independent).
Data analyses
Relative abundance index and non-metric dimensional scal- ing analysis Computation of the nMDS resulted in a stress value of 0.09, suggesting that the representation was a good fit for the data. All large carnivores were widely spread in the low dimensional space (Fig. 2), indicating a strong dissimi- larity between them. Large carnivores weremostly differen- tiated through the horizontal axis (MDS1), but lions and African wild dogs were also separated through the vertical axis (MDS2). Only four covariates were significant (P,0.05) and were therefore represented. The Spearman test of correlation showed a significant correlation (ĉ = 0.75) between the distance to the Niokolo River and dis- tance to the nearest river. Consequently, the distance to the
Oryx, 2024, 58(5), 664–675 © The Author(s), 2024. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605323001746
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