Effects Of Habitat Variability On Rodent Distribution And Diversity In Nairobi National Park, Kenya

Abstract

Rodents are among the most diverse and abundant vertebrates that occupy both natural and semi-natural habitats. Their diverse diet and contribution to predation food chain makes them suitable candidates for motoring environmental change due to human habitat alterations and pollution. The purpose of this study was to investigate the status of rodent populations in Nairobi National Park, a protected area that is facing immense pressure of urbanization and socio-economic activities in Nairobi City County. The specific objectives were to determine the rodent community structure and how habitat variability and human activities have influenced species diversity and relative abundance. Line transects were used to sample rodents in the main habitats: savannah grassland, upland and riverine forests, and human disturbed sites in Nairobi National Park during the dry and wet seasons. The results indicated that the park was not endowed with a rich diversity of rodent species. A total of 56 individuals belonging to five species were trapped during the study period. The five species were identified as Lemniscomys striatus, Hylomyscus sp, Rattus rattus, Mus mus and Otomys tropicalis. Rodent species diversity was therefore low (Shannon Weiner Diversity H = 1.40) while Pielou’s species evenness was moderate (J = 0.44), indicating that the rodent species occurred widely in all the major habitats in the park. Univariate generalised linear models indicated that rodent population abundance was influenced by season, vegetation type and habitat structural features. Human disturbed sites, such as residential compounds, camp sites and picnic sites as well as habitat edges found along roads and park boundaries showed significant variation in rodent abundance. Predictive multivariate models indicated that rodents were more abundant in all habitats during in wet season compared to the dry season. The seasonal abundances were also positively correlated with increased tree and shrub densities in the study sites. Rodent species richness was positively ix correlated with higher tree density while vegetation type had marginal effects the diversity of rodent species. It was concluded that the tropical savannah vegetation in NNP was not rich rodent species. There was no significant invasion of the park by feral rodents across the park boundaries or from human disturbed areas in the park. The abundance of rodents was influenced by season, and finer vegetation metrics but not human disturbance. Anthropogenic activities, such as camping, picnic, solid waste disposal and heavy tourist traffic did not significantly influence rodent species distribution and abundance. The invasive Rattus rattus was restricted to human occupied areas. The sample size obtained and sampling effort should be enhanced through further research so as to confirm the observations made during this study. However, this study has provided reliable baseline data and information that can aid future monitoring rodent species in Nairobi National Park.