Human–elephant conflict mitigation 743
incursion. The primary aim of our study was to determine whether elephants crossed the light barriers. Occasions during which elephants approached a field (i.e. came within a distance of , 30 m from the field) and turned away were defined as prevention (King et al., 2011). Assessments of elephant activities in and around fields
were dependent on timely feedback from farmers. When an incursion was reported, a member of our research team assessed the field, recording the location where the ele- phants entered the field, following the path they walked and estimating the group size based on spoor in the field.
Additional methods used to deter elephants
The trial of the solar-powered strobe barriers aimed to assist farmers in deterring elephants from entering their fields and to complement rather than replace other methods. Farmers were thus encouraged to continue defending their crops as they would have done without the lights. To take additional measures into consideration, we recorded the date of any elephant activity (incursion or prevention), and whether the farmer had used any other mitigation methods since the lights had been deployed. Farmers reported using the following additional deterrents: chilli peppers (in any form), banging a drum and using a battery-powered torch. We also recorded whether domestic dogs were present in the field, whether the farmer was present during the activity, and whether the Department of Wildlife and National Parks attended the report to determine if the farmer could claim compensation.
Statistical analysis
To determine the factors that deterred elephants from enter- ing a field (0 = prevention following approach, 1 = incursion following approach), we developed a series of generalized linear mixed models in R 3.4.0 (R Development Core Team, 2017), using the lme4 package (Bates et al., 2015). Models had a binomial error distribution and a logit link function. As we had multiple measures from each farm, we included farmer identity (N = 18) as a random term in all models. We used Akaike’s information criterion cor- rected for small sample size (AICc) to select the best model from a set of plausible options. All parameters, including presence of lights (yes/no), field size, whether the farmer engaged in one or more other active mitigation efforts (including the use of chillies, dogs, drums or torches; yes/no), distance to the nearest known elephant corridor, and the two-way interaction Treatment ×Other mitigation, were sequentially removed froma saturatedmodel.We com- pared the AICc of all resulting models with the previous model and retained parameters only if their removal inflat- ed AICc by.2 (Burnham et al., 2011), because lower AICc
values correspond to better relative support for a givenmodel (Akaike, 1974). To validate that there was no improvement to theminimalmodel,we returned all original parameters to the model one by one, thereby creating our model set together with the basic model that contained only the intercept and the random term.We then calculated Akaike weights to de- termine the relative importance (Akaike, 1974) of these final models. As the Akaike weight of the best model was , 0.9 (Grueber et al., 2011) and several models had deviance in the AICc ,7 units (Burnham et al., 2011), we conducted model averaging using the MuMIn package in R (Bartoń, 2012). We selected the top models with cumulative Akaike weights .0.95 to construct model-averaged estimates of the parameters (Grueber et al., 2011).
Results
We recorded a total of 107 elephant activities (incursions and preventions) over the two seasons in control and treat- ment fields, of which 49 were in the 2016/2017 season and 58 during the 2017/2018 season. Overall, more activities (count- ing both incursions and preventions) occurred in the treat- ment fields (80) than the control fields (27), but a higher percentage of activities resulted in preventions in the treat- ment fields (75%) than the control fields (30%). The likelihood of an elephant entering a crop field was sig-
nificantly lowerwhen lightswere present compared to control fields (z = 4.59 ± SE 1.66,P,0.05; Tables 2&3).Although in- cursions were recorded in fields equipped with strobe light barriers, we documented only two occasions where elephants crossed the light barrier. In one of these two incidents the farmer reported that the elephants were being shot at when they crossed the lights andwere leaving the field. In the second instance two of the lights were not working so the barrier was compromised. No elephants were captured by the camera traps erected facing the light barrier. Model 1 best fits the data with the fewest explanatory parameters and lowest AICc. Six models had deviance in the AICc ,7 units and were used in model averaging (Tables 2 & 3).
Discussion
The likelihood of an elephant incursion into a crop field was significantly reduced in the presence of a solar-powered strobe light barrier, supporting the hypothesis that lights are effective in deterring elephants at night-time. To our knowledge this is the first trial to test the efficacy of solar- powered strobe lights in reducing field incursions by ele- phants. The effects of solar-powered strobe lights were greater than the collective effects of any other deterrents (chilli pepper burning, guard dogs, torches or the banging of drums).
Oryx, 2021, 55(5), 739–746 © The Author(s), 2020. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605319001182
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