Gliding lizards and how disturbance helps biodiversity

Draco gliding lizards are interesting tropical animals. They have ‘wings’ that fold out from their ribs and allow them to glide from tree to tree. They also have a small flap under their chins that acts as both a flag to communicate and like the tail of a plane to stabilise their flight. When I read about them as a kid, they always struck me as incredibly exotic animals that would be really hard to find.  It turns out that they are quite well adapted to living in our cities.

There are 11 species of Draco in Peninsular Malaysia. In the natural world, they tend to be found in forest clearings where there is space between trees and not too much dense vegetation. These gaps between trees are usually created by tree fall events. In a mature rainforest, trees fall very often, either due to old age, disease, or unstable soil. Rainforest trees are often connected to other trees by vines or lianas, so when one tree goes down, it can pull down others and crush anything smaller in its path. This is a natural disturbance that creates gaps in the otherwise dense canopies of the rainforest. Young trees and saplings use this opportunity to fill the gap and start the cycle over again.

Many species are known to take advantage of these forest gaps, including gliding lizards. The constant disturbance of tree falls creates more diverse patches of forest, where trees of different species and ages are always going through tree falls and regrowth, nothing staying permanent. This, in turn, creates space for all sorts of gap species that are adapted to these environments. The layperson may view change and disturbance as something undesirable or negative, but these are necessary processes to keep the ecosystem in balance.

In cities, humans are the main force of disturbance. We cut weeds and shrubs and maintain clear gaps between trees. While this may not be good for animals that prefer some shelter, the lack of dense vegetation seems to be a boon for gliding lizards. They can bask in the sunlight created by our sparsely planted trees and glide in between them with ease. Scientists call this pre-adaptation – an organism is predisposed to survive in certain habitat structures, allowing it to take advantage of new habitats with similar features.

A lot of our urban species have, by luck of the draw, found a place for themselves in our urban spaces. So perhaps we should ask the question of how we should use disturbance as a tool for biodiversity and healthier ecosystems, instead of maintaining landscapes just for the sake of maintaining aesthetic practices.

References:

Whitmore, T. C. (1984). Tropical rain forests of the Far East. Oxford University Press, Oxford.

Grismer, L. L. (2008). A revised and updated checklist of the lizards of Peninsular Malaysia. Zootaxa, 1860(1), 28-34.