Distribution of Small Mammals Along Altitudinal Gradients in the Mid Mountain, Nuwakot, Nepal

Abstract

Diversity and distribution pattern of small mammals were studied along altitudinal gradients of a mid-mountain of Shivapuri Rural Municipality-1, Nuwakot, Nepal. The study aimed to assesses diversity and altitudinal distribution pattern of small mammal species and comparison of trap efficiencies. Live trapping of small mammals by three types of trap (Local Mesh Trap, Tube Trap and Pitfall Trap) were performed at five trapping sites of altitude of 1,200 m, 1,500 m, 1,800 m, 2,100 m and 2,400 m by making two trapping grids of 50 m × 50 m in each site. Small mammal diversity and distribution along altitudinal gradients were analyzed by calculating diversity index, community evenness, community similarity and β diversity. Chi-square test, correlation test, Kruskal Wallis test and simple correspondence analysis were used for statistical analysis of significance variations of species richness, associations of species richness with altitude and trap success rates. Eight species of murid rodent and two species of soricid shrew were observed with diversity index of 2.06 and overall trap success of 11.55%. Slightly decreasing trend in species richness along altitudinal gradients was observed. But the correlation between species richness and altitude was statistically insignificant (r = -0.41, p-value > 0.5). The small mammal species richness and community composition varied greatly along altitudinal gradients with variation of dominant forest vegetation, understory vegetation structures and habitat complexity. Apodemus sylvaticus was found to be the most abundant rodent species where both shrew species showed poor diversity than rodents. Niviventer eha, Mus musculus and Soriculus macrurus were observed at lower gradient and Apodemus sylvaticus and Alticola roylei were observed at upper gradients. Similarly, Bandicota bengalensis and Suncus murinus were trapped at the middle of altitudinal gradients. Trap success rates and species specificity of three trap types varied greatly from site to site. LMT trapped more species and individuals with more trap success rate. Larger and smaller body sized species were mostly trapped by LMT and TT respectively. Bandicota bengalensis and Rattus rattus were only trapped by LMT and Mus musculus was only trapped by TT. But PFT trapped mostly smaller and medium sized species. Three types of trap used for small mammal sampling showed supplementary role for diversity of small mammals. It is concluded that diversity and distribution pattern of small mammals along altitudinal gradients varies on the basis of dominant forest vegetation types, understory vegetation, habitat heterogeneity and complexity. And different types of trap showed complementary role for sampling of small mammalian community.