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.