**2.4. Exploring species distribution with abiotic characteristics**

rain shadow side of the Usambara Mountains (plateau). The plain and escarpment receives annual precipitations of 400 and 800 mm, respectively. The average annual temperatures for plateau cold and warm zones are 14°C and 27°C, respectively, whereas the relative humidity is 70%. Temperatures in the plain range from 25 to 34°C per annum. The plateau grows diverse tropical crops and temperate fruits, while the plain has limited farming activities

**Figure 1.** Location of biogeography study area, in West Usambara Mountains, Tanzania.

West Usambara Mountains were formed by block faulting and repeated uplifting of Precambrian basement rocks between 180 and 290 million years ago [27, 28]. The geologic composition and variability in West Usambara Mountains depicts differences in terms of geology with regards to geomorphic position. The **plain** is mainly composed of duricrust calcareous yellow grey sand, whereas the geological rocks in the **escarpment** are gneisses mixed with undifferentiated granulites and distinctive bands of hornblende and pyroxenes. The geology in the **plateau** is mainly gneisses with leucocratic quartzo-feldspathic granulites and khondalites. There are few areas composed of recent alluvial materials like depressions

Visual observation of satellite images, stereoscopic aerial photographs and orthophoto maps (numbers 9480410, 9480400, 9470410, and 9470400) was done. Also, visual analysis of

and valley bottoms which are composed of mixed alluvial-fluvial materials [29].

**2.3. Determination of landform and soil characteristics**

except for sisal (*Agave sisalana*).

146 Pure and Applied Biogeography

**2.2. Geology of West Usambara Mountains**

Habitat or vegetation description was done in grids of 20 m × 20 m by estimate vegetation cover percentage. Spatial distribution of animal was done using two approaches. One was by trapping small mammals at sites where augering and/or soil (profile sites) were made using grids of 20 m × 20 m. The data were collected twice between December 2009 and March 2013. Traps of different types and sizes were employed to capture diverse mammal species such Sherman live traps, local made wire cages (for bigger sized small mammals like squirrel, genetta) and the pitfall traps, which are 10-l plastic buckets. The total numbers of traps used were 300 of which 270 were Sherman, 15 wire cages and 15 pitfalls. The traps were arranged in lines each with 10 trapping stations placed 10 m apart and left open during the day and night for two consecutive nights [32]. Traps were inspected every morning to remove trapped animals and replace the bait. Peanut butter mixed with maize bran, roasted maize grains and sardines were used as bait. The trapped small mammals were counted and recorded.

The second approach was use of a proxy, which was the rodent burrow. Total rodent burrows were estimated on the landscape. Rodents' burrows were scanned within grids of 20 m × 20 m at width of 0.5 m from one end of grid, return until finished. A number of burrows was recorded and the nearest to the centre was opened to see if the animal were in or how recent the use has been. Atmospheric temperature were measured using the infrared thermometer topsoil temperature were done using thermal couple thermometer. The topsoil relative humidity was estimated using iButtons buried 20 cm for 24–26 hours recording both relative humidity (%) and temperature (degree Celsius).
