The Impact of Human Land use activities and Seasonal changes on the Dung Beetle Diversity of Kakamega Forest Ecosystem

Abstract

Based on quantitative comparative data collected m Kakamega forest and the surrounding farmlands, analyses were done to ascertain to which extent different modes of land use and seasonal changes affect guild structure, abundance and species diversity of dung beetle assemblages. The human influences studied included extensive cattle farming and deforestation. These studies were performed between October 2002 and August 2003 during the short rainy, dry, start of long rainy and end of the long rainy seasons in the primary forest, secondary forest, grazed, and ungrazed grasslands in Kakamega forest and the Surrounding farmlands. The experiments were done by depositing 10 standard samples of lkg fresh cow dung on standard areas in the habitats in each season at night and during the day and the beetles were recovered using floating method. A total of 80 samples yielded a total of 21,604 dung beetles in all the habitats and seasons studied representing the families Scarabaeidae, Hydrophilidae, Staphylinidae and Histeridae. The tunnelers, dwellers, and rollers were the guilds represented in the family Scarabaeidae. For the effect of seasons on the dung beetles structure individuals and guilds were compared from different seasons The studies indicate that the extensive cattle grazing and forest degradation influence both the guild structure and abundance of dung beetles. There was high abundance in the grazed grassland, followed by the ungrazed grassland. All the studied habitats had a significant conditional effect on the families and the guild structure of the dung beetles and that different guild of dung beetles have strong association with different habitats. During the day the dwellers were strongly associated with the primary forest, tunnelers with the secondary forest while rollers, Staphylinidae and Hydrophilidae were associated with the ungrazed grassland. It is also shown that the dung beetle assemblages were significantly affected by seasonal changes and that the impact of the seasons on the dung beetle guilds is significantly influenced by human activities. The dung beetles were more abundant during the rainy seasons (start of long rainy and short rainy seasons) and fewer specimens were collected during the dry season. The tunnelers were strongly associated with the start of the long rainy and short rainy seasons at night while the rollers were strongly associated with the dry season during the day. At night, however, the tunnelers and the dwellers were strongly associated with the grazed grassland. In the forest areas a total of 55 species of Scarab beetles were collected. As shown by various diversity indices, and rarefaction plot, primary forest had higher species diversity than the secondary forest. However dung beetles were more abundant in the secondary forest. These studies have shown that differences in the beetle guild structure, abundance, and species diversity in Kakamega forest and the surrounding farmlands could be due to human land use modes and seasonal changes. The changes in the dung beetle assembleges were therefore significant predictors of susceptibility to habitat degradation