2.2. Field methods and analysis
Grid based surveys with total 96 sample plots each of size 20 m * 20 m in 6 sample grids (2 * 2 km2) with 24 sub-grids (500 * 500 m2) were used for locating pellets group. Preliminary field survey and discussions with the park staffs were done prior to field visit and the grids were selected based on the factor like, they represent all habitat types, the presence of species under consideration, accessibility etc. Direct field observation and pellet count method were used for this research. Pellet count method can easily determine the areas used intensively by animals (Julander, 1958). Pellets of the different species were distinguished from each other by their size and shape following Rivero et al. (2005) and with the help of local field assistant familiar with the wildlife species of the study area. During the observations, we recorded the habitat types where we located the pellets. Levin’s measure of niche breadth was calculated for all species under study based on equation given below (Krebs, 1999).
\begin{equation} B=\frac{1}{{\sum\text{Pi}}^{2}}\nonumber \\ \end{equation}
B’ = \(\frac{B-1}{n-1}\)
Where,
B = Levin’s measure of niche breadth
B ’=Standardized niche breadth
p i= Proportion of individuals found in or using resource state i
n= number of possible resource state
The percentage of cover overlap between species pair or spatial overlap was determined by knowing the number of plots shared by species in the sample grids. The proportion of different habitat types used by different species was determined based on field study results. Then Morisita’s index was used to determine the resource overlap between the pair of species as described in (Krebs, 1999). The index values range from 0 to 1. Zero represents no overlap whereas 1 represents maximum overlap. Three levels of overlap were defined as done by Jung & Czetwertynski (2013) as high overlap (≥0.80), moderate overlap (0.40-0.80) and low overlap (<0.40).
\begin{equation} c=\frac{2\sum_{i}^{n}{p_{\text{ij\ .\ \ }}p_{\text{ik}}}}{\sum_{i}^{n}{{p_{\text{ij}}}^{\frac{{(n}_{\text{ij}}-1)}{(N_{j}-1)}}+}\sum_{i}^{n}{p_{\text{ik}}}^{\frac{{(n}_{\text{ij}}-1)}{(N_{j}-1)}}}\nonumber \\ \end{equation}\begin{equation} \sum_{i=1}^{n}{n_{\text{ij}}=N_{\text{j\ }};}\sum_{i=1}^{n}{n_{\text{ik}}=N_{k}}\nonumber \\ \end{equation}
where,
c = Morisita’s index of niche overlap between species j and k
p ij= Proportion resource i is of the total resources used by species j,
pik = Proportion resource i is of the total resources used by species k,
n ij, = Number of individuals of species j that use resource category I,
n ik = Number of individuals of species k that use resource category I,
Nj, Nk = Total number of individuals of each species in sample.