Flying foxes are vanishing from the city and its suburbs. The Zoological Survey of India (ZSI) is conducting a research and plans to include this finding in its survey report on fauna in West Bengal, to be published soon.
“This is not a bat census. But our preliminary investigation confirms that the bat population in the city and its suburbs is dwindling,” said M.K. Ghosh, ZSI expert on bats and rodents. The decrease is more pronounced in the case of the species that survives on fruits, he added.
Experts attribute the phenomenon of the vanishing bats to indiscriminate destruction of greenery and orchards and the mushrooming constructions by demolishing old buildings. “We believe the shrinking of its habitat is at the root of the decrease in the bat population,” Ghosh said.
Director of Calcutta Zoological Garden Subir Chaudhury agrees. Colonies of roosting bats can still be seen in the trees of the zoo, but the keepers claim that their count has dropped.
“Those are free-living bats that survive on fruits,” according to Chaudhury. At dusk, he said, these bats take wing to the fringe areas of the city in search of food. They are back before daybreak.
Chaudhury held that their restricted food habits and the gradual disappearance of orchards was behind the dwindling number of bats.
Similarly, because of its restricted food habits, Chaudhury said, the ant-eating pangolin was turning rare. The pangolin feeds on ant eggs.
The ZSI expert said bats of a number of species — insectivorous or fruit-eating, including the False Vampire — are found in Calcutta and the districts. False Vampires are not really vampires, he pointed out. They live on small animals, like birds, lizards and frogs.
In tandem, the Asian Development Bank (ADB), in its preliminary survey on Calcutta’s Environment Improvement Project, prepared by Australian firm Aegis, pointed out that urbanisation had taken a toll on more than 150 species of birds and 17 species of mammals in the city over the past 35 years.
During the 1960s, when reclamation of wetlands for Salt Lake started, ZSI recorded 22 species of mammals and 248 species of birds on the eastern fringes of the city. Now, after about 35 years of urbanisation, the number of mammal species there has dwindled to only five. The bird species count has dropped to 64. A new breed of marsh mongoose that was discovered there in the 1960s has vanished from the wetlands.