Nature is a dynamic 24X7 business arena, where mammals, birds, insects, busily work during daytime for their food and survival. But what about their activities at night, especially in case of diurnal (active during daytime) ones that are not been designed to be active at night. What they do at night? Do they sleep at night? If yes, where they would rest? To know the answer for this intriguing questions, I started to observe birds first in my campus*. I could get closer look on birds, especially shy ones like Grey Francolin (Francolinus pondicerianus) and swift-flyer like Common Tailorbird (Orthotomus sutorius) which are otherwise difficult to see from close quarters during the day. Besides looking at birds, I found several colourful butterflies that are adding radiance by their presence to the forest, and thus I started my survey on butterfly roosting (resting).
Butterflies are nature’s wonders. Their mere presence gives rejoice and fulfilment. They enthral human singly and in groups at daytime. Especially during migration period, watching a cluster of butterflies hovering is an incredible experience. Nocturnal roosting is one of the survival strategies of these cold-blooded Lepidopterans to beat the cold weather and to remain inconspicuous during their non-active periods (night). And, yes, they roost (sleep) at night.
Butterflies select their roost site – i.e. a dry place with low light penetration, a place to protect them from wind, rain, and bird predation. During this study, they are noted roosting under the leaf, among the well leaf-covered bushes. It is their tactics during windy or rainy nights to protect them from getting wet. But, to my surprise, Red Pierrot (Talicada nyseus) was daring to roost at the terminal end of the dry plant that makes them easily noticeable. This is a tricky approach unique of its own kind, as the approaching bird must spend tremendous energy to hover at the tip of the plant, where they don’t have enough space to perch, for an easy catch. These colourful Lepidopterans comes back to the same roost sites on every night.
Common Gull (Cepora nerissa), Three-spot Grass Yellow (Eurema blanda), Plain Tiger (Danaus chrysippus), and Red Pierrot were repeatedly seen roosting in Lantana camara plant. Lemon Pansy (Junonia lemonias), and Common Emigrant (Catopsilia pomona) were seen resting in Chromolaena odorata shrub. Butterflies were noted roosting majorly on plants and shrubs and comparatively less in trees. Most of them are roosting in single. Nevertheless, once two Blue Tiger(s) Tirumala limniace were noted roosting together and also observed roosting along with Plain Tiger (Danaus chrysippus). Roosting in groups prevents them from bird attacks. Yet again a survival strategy.
I have observed roosting of butterfly species like Common Emigrant (Catopsili apomona), Mottled Emigrant (Catopsilia pyranthe), Common Jezebel (Delias eucharis), Red Pierrot (Talicada nyseus), Common Gull (Cepora nerissa), Common Crow (Euploea core), Indian Sunbeam (Curetis thetis).
These butterflies prefer an environment with drier condition, close to ground cover, an undetectable place with protection from cold and wind, during their less-active period of the day. It also emphasizes that butterflies also select a place to have a secured rest at the end of the day, just like humans to start the next busy day, to compete with the butterflies of the same species and other species, to get a good pay-off in their survival contests.
* – Sálim Ali Centre for Ornithology & Natural History (SACON) campus. It is the institute where I pursue my Ph.D.
P.S. Italics are the scientific names of the butterflies preceding the brackets.
This article was published in SACON newsletter Vol. 11(4): October – December 2014 (Page 4). Newsletter of SACON