Abdul Wahab Khan
Panaji
A study has uncovered the critical ecological factors that influence how the Indian giant squirrel (Ratufa indica) selects its nesting trees in Goa’s Bondla Zoological Park.
The squirrels show a strong preference for tall, mature trees with large girths, particularly deciduous species, according to
the research.
The study, published in Mammalian Biology, has been authored by Ashish Kumar Yadav and Paresh C Porob of the Goa Forest Department and Stephen Jonah Dias of Edinburgh Napier University, UK. It was conducted over several months
in 2024.
It is the first investigation of its kind from Goa, where the Indian giant squirrel thrives amid both wild habitats and human-influenced landscapes.
Although the Indian giant squirrel is listed as a ‘least concern’ species on the IUCN Red List, its populations face mounting threats from habitat loss, hunting, and forest fragmentation.
The research team carried out extensive fieldwork between January and June 2024. Using Nikon binoculars and handheld Garmin GPS devices, they located squirrel nests—known as dreys—within Bondla’s moist deciduous forests. A total of 119 nests from 112 trees were mapped. For each nesting tree, a 20-metre circular plot was established, including both nesting and
non-nesting trees.
Ten ecological parameters were meticulously measured.
These were tree species, vegetation type, tree height, girth at breast height, number of primary and secondary branches, canopy cover, the presence of climbers, parasitic plants, and canopy continuity.
The researchers analysed the data using R software (v4.4.0), employing generalised linear models (GLMs) with binomial errors to determine which variables most strongly influenced nest selection. The models were ranked using Akaike’s Information Criterion (AICc).
They have noted, “The top model contained all measured variables…indicating that nest site selection by R. indica is influenced by multiple ecological factors.”
The squirrels showed a strong preference for tall, mature trees with large girths, particularly deciduous species. Terminalia tomentosa emerged as the most favoured tree, accounting for 42 per cent of all nests.
Secondary branching also played a key role: “The probability of nest presence increases with the number of branches on the tree,” the authors observed.
Other critical factors included the presence of climbers and parasitic plants, as these provided both nesting material and potential food sources. Canopy continuity—overlapping branches that allow squirrels to travel without descending to the ground—was another significant determinant, offering both mobility and protection from predators.
Interestingly, canopy cover alone did not significantly influence nest placement, likely because data were collected during the leaf-fall season. Nonetheless, the overall model confirmed that all ten ecological parameters interacted to shape nest selection.
The study has emphasised the giant squirrel’s dependence on mature, interconnected forest habitats.
“The larger girth and taller trees indicate a mature forest, with a sufficient canopy cover and connectivity, which are essential for the species’ survival,” the report has said.
By uncovering the specific tree and habitat characteristics that these arboreal mammals rely on, the research has underscored the urgency of protecting Goa’s remaining natural forests. With increasing human pressures—from logging and plantations to infrastructure projects—such findings provide a scientific foundation for conservation policies.
“The results of this study highlight the ecological variables influencing the nesting tree selection of R. indica in a protected area of Goa, and the role of such areas in the ex-situ conservation of the species,” the authors have noted.
