Status and Distribution of Malabar Giant Squirrel Ratufa indica in Western Ghats of Maharashtra, India



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Chapter 7

Status of Malabar Giant Squirrel in the Study Area



7. 1 Distribution of Giant Squirrel in the Study Area
The pattern of occupancy by giant squirrel in Maharashtra Western Ghats is demonstrated in three maps based on predictive model, conditional model and records of detection and non-detection history respectively.
The predicted estimated occupancy rate of 0.95 (SE 0.03) indicates that in Western Ghats of Maharashtra, the probability of occupancy by giant squirrel is 95 percent or Proportion of Area (POA) occupied by giant squirrel is about 95 % with a detection probability of 0.61 (±0.05). For most grids the probability of occupancy was predicted to be high (0.84 - 1.0), which means that the probability that squirrels occur there or chances of squirrels occurring are high. In other grids, which have lower occupancy (0.0009 - 0.3848), the probability or chances that squirrels occur are much lower.
One of the reasons for having high predictive occupancy estimates is that the survey was carried out only in grids having semi-evergreen and moist deciduous forest with tall trees and dense canopy which is considered to be optimal habitat for the squirrels. Most of these forest patches did have some signs of squirrel presence. Sub-optimal habitats such as dry deciduous and scrub forests were not sampled in the grids therefore all grids having squirrel presence scored high on its occupancy estimates. Secondly, although the sampling was carried out in smaller grids of 4 km2, occupancy estimates were considered for the main grid of 20 km2. This was done to obtain a broader pattern of distribution. If the analysis had been done at the sub-grid level, it would have yielded occupancy estimates at finer scale which is not desirable at the landscape level.
Giant squirrel occupancy was influenced majorly by the disturbance index and average slope in the surveyed area. Disturbance index included signs of tree cutting and lopping since it has a direct impact on the forests by creating gaps in the canopy. Grids that had higher signs of tree cutting had lower occupancy rates. Similarly, areas with higher slopes affected the presence of giant squirrels negatively. This could be an artefact of geology and topography of the area. The volcanic ranges of Maharashtra Western Ghats have steep escarpments with lateritic and basaltic soils. Because of its rocky substrate, the crestline and plateaus have short but often dense forests and the slopes are barren or support thickets of dwarf stunted trees such as Syzygium, Actionadaphnae with an under storey of Memecylon and Carvia callosa. Such vegetation does not provide suitable habitat for giant squirrels. This topographical feature is exclusive to Maharashtra Western Ghats and is not seen elsewhere. In southern Western Ghats, Srinivas et al (2008) found giant squirrel distribution higher in areas with undulating terrain because in their study area, moist and evergreen forests were found on the higher slopes.
Forests are scanty on steep slopes and deep in the valleys in surveyed areas


Evangeline Arulmalar
In some grids in the coastal region, such as Srivardhan Range in Roha Division, high occupancy is predicted in spite of no detections (Refer to Figures 5.1, 5.2 and 5.3). The occupancy model predicts high occupancy but field survey showed total absence of giant squirrel. There are two possible reasons for this: one is that being a coastal area, the slope is very low which is one of the covariate used in predicting high squirrel occupancy. This is unlikely to be correct based on the experience of the survey team. The robustness of the model for the plains region needs to be improved by providing more data points (surveying more grids) in this region
Edge density per patch was expected to be negatively co-related to the occupancy of squirrel since more edge would result in more fragmentation and hence lower occupancy by squirrels. However, edge density showed a weak positive correlation to occupancy estimates and did not contribute significantly in explaining the occupancy by giant squirrel.
In KMTR, the estimated occupancy rate of giant squirrel was reported to be 0.82 (SE 0.08) with a detection probability of 0.71(±0.05). Although KMTR is a Protected Area, the overall occupancy rate was lower than the estimated rate in this study. As mentioned earlier, degraded habitats were not surveyed in our study while in KMTR, grids with degraded scrub thorny forests, and Mundantharai plateau were also sampled that would have contributed to lowering the overall occupancy estimates of giant squirrel in the area (Srinivas et al 2008).
7.2 Relative Abundance of Giant Squirrel
The density of Malabar giant squirrel in Bhimashankar was highest in the study area but it is lower than earlier estimates from Bhimashankar by Borges et al (1998). The density in Bhimashankar is comparable to density estimates from moister forests of Bhadra Tiger Reserve. Overall high density of squirrels from moister forests indicates that moister forests can support higher population of giant squirrels.
Table 7.1: Density Estimates of R. indica from Northern and Southern Western Ghats





Moist Forests of Bhimashankar

Moist Forests of Maharashtra Western Ghats

Moist Forests of Southern Western Ghats

Drier Forests of Southern Western Ghats

Borges et al

100/km2

NA

-

-

This Survey

15.89/km2 (11-22)

2.9/km2

-

-

Other Surveys

-

-

31 /km2 Parambikulum WLS (Ramachandran 1988), 11 to 64 /km2Indira Gandhi WLS (Umapathy and Kumar 2000), 5.5 and 8.5 /km2 in Alkeri and Nalkeri in Nagarhole (Madhusudan and Karanth 2000), 10.4 to 12.3 /km2Bhadra TR (Jathana et al 2008)

2.3 to 4.8 /km2Bandipur and Nagarhole (Jathana et al 2008), 2.8 /km2Mudumalai (Baskaran et al 2011)

Excluding Bhimashankar, other surveyed areas in Maharashtra Western Ghats had a much lower density of squirrels. The forests in these areas are similar to Bhimashankar with semi-evergreen and moist elements but density estimates are much lower than in Bhimashankar and is closer to the estimates of density from drier forests of southern Western Ghats.




Closed Canopy Forest of Bhima 1 and Fragmented Forests of HKS


Tushar Pawar and Prachi Mehta
Another indication of lower abundance of giant squirrel in surveyed sites is obtained by comparing commonly used index of encounter rates. Encounter Rates were compared between sites and between Maharashtra and Southern Western Ghats.
Table 7.2: Relative Encounter Rates of R. indica in the Study Area


Protected Area

Sighting

New Nests

HKS

0.08 (0.04)

2.3 (0.38)

Bhimashankar

0.7 (0.16)

12.3(1.43)

SGNP, Tungareshwar

0

0

Tansa

0

0

Phansad

0.03

7.57 (2.99)

Koyna

0

5.5 (1.7)

Chandoli

0

2.1(0.8)

Radhanagri

0.3(0.3)

5.4(2.3)

Reserved Forests

Sighting

New Nests

Nashik

0

0

Malshej Ghat

0.09(0.08)

4.4(1.7)

Thane Division

0.02 (0.02)

0.8(0.4)

Junnar Division

0.3(0.15)

4.8 (2.0)

Pune Division

0.3(0.16)

7.0 (1.3)

Roha Division

0.1(0.11)

5.6(2.4)

Raigad Division

0.04 (0.04)

0.4(0.2)

Satara Division

0.2(0.09)

6.3(1.3)

Kolhapur Division

0.05(0.03)

2.7 (0.5)

Figures in parentheses represent standard error

Average encounter rate of giant squirrel from Maharashtra was 0.33 while within Bhimashankar it was highest at 0.7 (0.16). Excluding Bhimashankar, the overall encounter rate dropped to 0.18 from the remaining surveyed areas. Kumara and Singh (2006) reported an encounter rate of 0.27 from wet forests of Western Ghats of Karnataka. Between individual sites, encounter rates were highest in moist forests of Srinegri (0.8) followed by drier forests of Nagarhole (0.34), Sirsi (0.24), Brahmagiri (0.21) and Pushpagiri (0.1). Jathana et al (2008) reported lower encounter rates from drier forests of Bandipur (0.17) and Nalkeri (0.29) and moderately high from moister forests of Sunkadakatte (0.36) and higher encounter rates form wetter forests of Lakkavalliee (0.54) and Muthodi (0.6) areas of Karnataka. In the study area, somewhat similar estimates were observed from divisions of Junnar (0.3), Pune (0.3), Satara (0.2) and Roha (0.1). Lowest encounter rates were in Malshej, Thane, Raigad and Kolhapur Divisions.



Lower abundance of giant squirrel in Maharashtra Western Ghats indicates that because of degradation, fragmentation and canopy breaks, the moist forests in the region are not able to support giant squirrels in higher abundance. These abundance measures are similar to those reported for dry deciduous forests in southern Western Ghats. Hunting of squirrels is a likely cause for suppressing the densities but except it a few cases, active hunting was difficult to establish in the study area.

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