| dc.description.abstract | Abstract
This study was conducted in Gachoka division of Mbeere district Kenya, between the
months of September and December 2001. The aim of the study was to establish how
patterns of land use influences the diversity, distribution and abundance of small mammals
in various habitats types under varying human influence and assess which of the measured
habitat parameters strongly influence diversity of rodents, information which is hitherto
not well documented in Gachoka division of Mbeere district. The study also sought to
determine how land use practice influences habitat conditions with a view of identifying
possible indicator species for the site. Various habitat factors, such as plant species
composition, percentage vegetation cover, plant density and diversity, burrows, and
mounds, all of which influence diversity, distrib~tion and abundance of small mammals
were determined in various land use types in the semi-arid region of Mbeere district.
Data on rodent abundance was collected through rodent captures on square grids of 64 live
traps, set out over an area of 70m ~7E)m in four land use types, namely cultivated, grazing,
fallow and bushy sites. All rodents sampled were identified to species level. Data on
vegetation parameters was obtained through a habitat survey conducted using transects.
The number and composition of woody plant species, number of burrows and mounds
were estimated in each transect. Grass species composition, percentage cover and soil
depth were measured in 1m by 1m quadrants placed at 10 meter intervals along the transect
line. The area sampled for habitat parameters corresponded with trapping points of small
mammals.
A total of 213 specimens comprising of five species of Murids were recorded. Three
species, Lemniscomys barbarus (Linnaeus), Otomys thomasi (Thomas) and Acomys
percivali (Dollman) were the most abundant with percentage abundance values of 35.6%,
35.2% and 16.4% of total captures. Burrows were found to occur with greater incidence
near the edges of cultivated areas while in uncultivated (fallow and bushy grassland) sites
burrows were situated under trees and shrubs alongside mounds. Mounds distribution was
associated with distribution of woody plants. However, no relationship between mounds or
burrows to particular plant species was observed although both tended to occur less
frequently under trees than shrubs. Unlike burrows, vegetation cover was correlated with
abundance of rodent species.
Bushy grassland and fallow sites provided greater diversity of plant (H' = 1.20; 1.21) and
small mammal species (H' = 0.5; 0.7) resp,ectively, compared to cultivated and grazed
lands. Abundance of Lemniscomys barbarus and Acomys percivali was found to be
greatest in uncultivated (bushy and fallow) sites, while Otomys thomasi was dominant in
cultivated and grazing sites. The fallow land, which is considered intermediate between
cultivated and bushy sites (based on the measured habitat £.'lra~eters), had the highest
diversity of trees/shrubs (H' =•1.21), grass (H' = 1.08) and small mammal species (H' =
0.7). This site hosted all of the five species of rodents in varying proportions.
This study demonstrates that non-opportunistic small mammal species like Arvicanthis
niloticus was restricted to natural bushy environment, and therefore requires persistence
such habitats to survive. Bush clearing in this area therefore jeopardizes the future survival
of the species. The rodent species composition in Mbeere was nevertheless found to be
comparable to that of other semi-arid areas in East, Central and part of Southern Africa,
15° Nand S of equator. | |
