ECOLOGY OF SMALL MAMMALS IN HUMAN-MODIFIED HABITATS NEAR THE WESTERN SHORE OF LAKE ABAYA, SOUTHERN ETHIOPIA

Abstract

Farmland protected area interfaces suffer severe anthropogenic land use/cover changes worldwide. The human-modified habitats in the Abaya-Chamo Basin (ACB) allow studying what their effects are on small mammal assemblage and new types of conflicts. This study was aimed at investigating: (i) the assemblage of small mammals in rather recently developed mosaic agro-ecosystem and reveals the role of uncultivated areas for ecosystem functioning and (ii) the dynamics of rodents and their damage to crops in smallholder farming systems. For these purposes, farmers‟ perspectives of rodent pests and available rodent pest management practices were surveyed and the survey results motivated our research in the ecology of the small mammals, to support farmers‟ claims with empirical evidences. Using our landscape-level sampling data, we addressed how season and habitat affect diversity, abundance and reproductive state of small mammals. The findings highlighted that (i) Mastomys erythroleucus is a generalist rodent species more responsible for the crop damage, (ii) small mammal species limited to habitat relics (e.g., Gerbilliscus phillipsi, Lemniscomys macculus and Elephantulus rufescens) are more likely to suffer local extinction and (iii) uncultivated areas support higher small mammal diversity including the vulnerable Ethiopia endemic arboreal species, G. minnae. The results call for landscape-level nature conservation that would also contribute to sustainable rodent pest management. Then we investigated farmland scale small mammal dynamics in response to variations in rainfed maize cropping stages, using capture-mark-recapture trappings in a permanent grid, before land preparation for maize planting, at 4-leaf, 6-leaf and maturity stages of maize crop and during fallow period soon after harvest, in two years (2019 and 2020). From this investigation, we concluded that: (i) the abundance and biomass of the two co-existing pest rodents (M. erythroleucus and Arvicanthis niloticus) follow maize cropping stages while they were breeding throughout the rainfed maize growing season and (ii) the period when the field was covered with crop supported higher small mammal diversity than when it was fallow. The results suggest consideration of vulnerable crop stages for targeted rodent pest management. Subsequently, we hypothesized that: (i) rodent pests of maize crop prefer more hedge field border to field centre and (ii) the extent of crop damage would be higher near hedge border than near field centre and its open border. To verify this, we selected three smallholder maize fields, each surrounded by one hedge and three open borders and set each 100 x 100 m permanent grid, during the long rain maize growing season during two xi years (2019 and 2020). Rodent damaged young maize plants and maize stems with rodent damaged cobs were counted in a sampling space of 10 maize planting holes × 4 maize rows at 5, 10, 20, 30, 40 and 50 m on each of the three parallel transect lines running from opposite facing hedge and open borders to the field centre. Soon after assessing rodent damage at each crop stage, we conducted overnight trapping of rodents in each grid to relate their densities to the extent of the crop damage they cause. From this setup, we showed that both the overall number and reproductively active individuals of the pest rodents (M. erythroleucus and A. niloticus) were higher close to the hedges and caused significantly higher crop damage. These findings suggested spatial and crop stage considerations for tailored rodent pest management.When consumed by the policy makers, these findings would explore ecologically based rodent management in the region.