Grizzled Giant SquirrelAmong the popular species of the Anamalais and indeed many other parts of the Western Ghats are the giant and flying squirrels. Although the scientific community is increasingly aware of the unique niche that these rodents occupy in the rich and threatened ecosystem of the Ghats, there is not much knowledge on the distribution, ecology and conservation status of most tropical squirrels.

DiscoverWild looks at some of the research findings presented at the International Tree and Flying Squirrel Colloquia held at Thekkady Periyar Tiger Reserve, Kerala from March 22 to 27, 2006. This feature is based on the book of abstracts produced for the Fourth International Tree Squirrel Colloquium and the First International Flying Squirrel Colloquium.

Arguably, the best-recognised species of squirrel in the Western Ghats is the Indian or Malabar Giant Squirrel, Ratufa indica. Research into the ecology of this endangered diurnal and arboreal squirrel seems to indicate that particular species of trees are of critical importance to it. Data on tree usage by the giant squirrel points to the applicability of the Pareto principle: at least some individuals were found using 20 per cent of the trees in a territorial area 80 per cent of the time.

Such a finding highlights the importance of identified tree species for the long-term survival of the giant squirrel. Selective logging in the Western Ghats even in a controlled setting is therefore likely to have an impact on the prospects of Ratufa indica, which uses particular tree species more for food resources, nesting, resting or as transit points. Members of this species prefer native species to exotic species for nesting.

Giant squirrels feed on a variety of items, such as seeds, leaves, flowers and bark. Seeds of Xylia xylocarpa, Dillenia pentagyna, Terminalia crenulata, Radermachera xylocarpa, Cordia wallichii, Zizyphus oenoplia, Schleichera oleosa, Terminalia bellirica, Grewia tiliifolia and Dalbergia volubilis; bark of Lagerstroemia microcarpa, Grewia tiliifolia, Terminalia paniculata, twigs of Lagerstroemia microcarpa, Stereospermum colais, Bridelia suamosa and Terminalia paniculata; leaves of Ficus sp., Lagerstroemia microcarpa, Tetrameles nudiflora, leaf petioles of Grewia tiliifola and flowers of Dillenia pentagyna, Xylia xylocarpa, Terminalia crenulata and Dendrophoe falcata are consumed by the species. 

Indian Giant SquirrelLianas contribute significantly to the diet of the giant squirrel. These plants are structurally weaker and less loaded with quantitative defensive chemicals and therefore important in the diet of the species. This view is strengthened by the finding that phytochemical evaluation of 271 plant parts across 45 species (35 trees and 10 lianas) for 21 phytochemical parameters reveals a significant contribution of lianas to the diet of the Indian giant squirrel. These plants are also used as physical pathways by squirrels and they could provide protection against predation.

The colloquia reviewed the evidence emerging from a study by the Nature Conservation Foundation, Mysore, pointing to higher abundance of the giant squirrels in private land proximate to the Indira Gandhi Wildlife Sanctuary, in the Anamalais in comparison with fragments of evergreen forests within the IGWLS. 

In their studies using line-transect methods, the team of researchers from the NCF encountered the giant squirrels at the rate of 1.4 in a 100-hectare patch within the IGWLS, as opposed to 9.6 in a 32 ha fragment of private land. This data would serve as a baseline for future studies on the impact of habitat fragmentation on Ratufa indica

The efficacy of using line transect methods to estimate densities of R.indica was outlined at the conference in a paper presented by the Wildlife Conservation Society, Bangalore. Highlighting the importance of spatial sampling and detectability in sampling work done using line transects, the paper provides results of densities in some forests of Western Ghats.

The WCS studies indicate that the densities ranged from 2.37 squirrels per square kilometre in Bandipur to 4.55 in Nalkeri, 4.86 in Sunkadakatte, 10.20 in Muthodi and 12.26 in Lakkavalli.

Indian Giant Flying SquirrelResearch into the flying squirrels by a team of the National Institute of Advanced Studies, Bangalore has focussed on the nest hollows and the relationship between disturbance to the forest structure and the creation of cavities.

Petaurista philippensis, the flying squirrel is investigated in this study in the Valparai plateau of the Anamalai hills, to determine whether fragments of forest with different levels of disturbance cause variation in hollow availability.

It was found that density of trees with hollows was greater in the least disturbed patch but there was no significant difference in the density of trees with hollows (trees with up to 5 hollows) in the three lots.