ELEPHANT WOODY VEGETATION INTERACTION AND HUMANELEPHANTS CONFLICTS CONTROL IN MWEA NATIONAL RESERVE

Abstract

Elephants respond to management actions like fencing and indirect disturbance, causing detrimental effects due to spatio-temporal variability in the intensity of habitat use. Reduced dispersal area of the fenced-isolated 42 km2 Mwea National Reserve and a growing density of 2 elephants km-2 may impede the savanna ecosystems’ equilibrium between elephant and tree densities. This study, aimed at determining the elephant habitat preference, their impacts on woody species and effectiveness of electric fence in control of Human Elephant Conflicts (HECs). A randomized block design was used to select 40 belt transects distributed proportionately in the four main vegetation types for sampling of woody species utilization parameters and elephant dung pile count. Evaluation of the fence effectiveness and locals’ opinions towards the reserve was by review of HECs records and interviews. Fixed Kernel buffers on dung density inferred a high preference for habitats within proximities of Tana and Thiba rivers. Mean dung densities showed that elephants preferred bushland, woodlands and grassland in descending order respectively (F (3, 36) =7.36, p<0.001). Acacia ataxacantha, A. brevispica and A. tortilis, were the elephants’ most preferred woody species and their mean heights correlated negatively with elephant dung densities. Elephants utilized their preferred woody species in significantly different modes (G (18, N=756) =178.23, p< 0.000) depending on the woodiness of the tree. The main stems of A. tortilis were broken off (61%) and debarked (20%), the other shrub species were browsed selectively (90%). It was evident that elephants severely affected their preferred woody species by impeding their height, damaging exploitation and surpassed utilization threshold of 50% per species. The opinions of residents from the fenced and unfenced sides on the electric fence effectiveness in control of HECs differed significantly (χ2 (1, N= 90) =29.11, p<0.0001). On average, they rated the fence as 76% effective. The fence effectively deterred the elephants but there was positively correlated (R2=0.25) HECs in the open edges against elephant population over 5 years. This was due to the 'funneling' effect of the linear fence design that pushed elephants to the open riversides. The long-term sustainability of the elephant forage and reserve-community relationship is henceforth at risk and worse even when the propensity of the impact’s magnitude increases exponentially with the elephant population growth over time. I recommend that the reserve’s carrying capacity for elephants be determined to obviate the negative impacts associated to high elephant population density.