Anti predatory behaviour of hibernating and hissing peacock butterfly (video below)
Many people I speak to and teach do not realise that some species of butterfly here in the UK actually hibernate as a butterfly. Those that do include the comma, peacock, brimstone, small tortoiseshell and I have seen adult cabbage whites hibernating inside my garage roof. Most hibernate as an egg, pupa or caterpillar. One adult hibernating butterfly is the peacock butterfly (Inachis io), which can hibernate for seven to eight months. How does it manage not to become a prey item, even when hibernating? With its rusty red base coloured wings and its distinctive four eye spots it can often be found near stinging nettles, upon which its caterpillars feed. Not withstanding current weather conditions and trends, this gloriously coloured butterfly is a regular garden visitor, although over the past few years I have not seen anywhere near as many as I usually do. The colours may appear beautiful to us, but to the peacock it is a just one part of its life saving strategy, which as an adult can live for 11 months, has to be successful to avoid predation.
Anti predator survival strategies
Even though they are soft bodied and in the main slow moving, butterflies have numerous ways to escape becoming a tasty morsel for other species, for example birds. These could include, flight, camouflage, mimicry, shape, being distasteful, defensive marking and hibernation. Even sound as you will see in the video below. Hibernation poses different problems in that the butterfly is static and therefore cannot fly away. In the main they rely on crypsis, i.e. avoid being found. Peacock butterflies mimic a dead leaf. Brimstones, commas and small tortoiseshells fall into this category.
Behind my shed and under a roof were two dry tyres, inside one of which I found this peacock butterfly hibernating! Note its dead leaf like colour and shape. They usually hibernate in dark crevices, holes in trees and inside hollow trees. I have found them on the roof of my garage and in sheds. But never a tyre!
If you invert a photograph of a peacock butterfly with its wings fully open, you will see that its body resembles that of a bird’s beak in shape and colour. The ‘eyes’ are correctly positioned either side of the beak, making it look more like an owl looking out from behind the larger forewings. Even the shape resembles an owl’s head, with its two small ear tufts on the ‘top’ of its head. Remarkable!
When it lands on plants etc., its wings are closed and even when basking will open and close its wings if it feels threatened. When closed the underside camouflage looks like either a dead leaf or tree bark, especially when it has landed on a tree trunk. If a bird did go to investigate a sudden flash of the peacocks wings would soon act to deter most birds! A harmless dead leaf or tree bark turns into an owl!
Camouflage to bluffing shock tactic.
Researchers undertook some fascinating work on this very aspect. Leaf mimicking butterfly species, comma, small tortoiseshells and peacocks were placed into a large cage along with some blue tits, which will eat butterflies. The coma relied on being the most perfect leaf mimic as its only defence, never revealing itself by opening its wings. Which worked for a while as it was the last species to be discovered. BUT nearly 75% were eaten. The small tortoiseshell was more conspicuous than the coma and did open and close its wings, but the wing pattens are not as stark a shock as that of the peacocks and it did not open up as many times as a peacock. Consequently more than 90% were eaten! The peacock fared best, by keeping still and remaining cryptic until the bird was almost upon it suddenly and with more frequency flashes its ‘owl’ wings and by making a hissing sound ensured it had 100% survival. A much more aggressive and intimidating defence than the other two species. In later research the same team found that when some of the eye spots were painted out, birds more readily ate the peacock butterflies except those ones that had full spots and displayed the intimidating behaviour as described.
What to do next?
Once the startled bird, instead of finding a meal finds itself to be a potential meal flies away, then what does the peacock do once it has revealed itself? It adopts one of three behaviours. Either keep its wings open but motionless fully exposing the ‘owl’. Continue to flick its wings with some butterflies seen during wing flicking, to tilt its body to rotate and match the movement of the bird possibly to increase its intimidating effect. In other words my eyes are watching you! Lastly it could remain still with its wings closed reverting back to its dead leaf camouflage.
Chickens afraid of peacock butterflies!
Olofsson also found that even domesticated chickens were fooled by the ‘owl’ face when confronted by the peacock butterfly undertaking its defence strategy. The chickens became more wary, more vigilant and more likely to utter alarm calls associated with ground based predators and suggested that this was based on fear of predation rather than a fear of conspicuous patterns.
I moved the butterfly into the garage for safe keeping. You can clearly hear it making a rasping noise with its wings. It is not a hissing noise. It is likely that the wing flicks and hissing noises deters birds with the exposure of the ‘owl’. Olofsson and his team found the peacock butterfly produces sonic and ultrasonic sounds when hibernating in its dark wintering sites when encountered by mice who will eat hibernating butterflies. Flashing its wings to show the ‘owl’ simply would not work in the dark. The sound made the mice flee and those that had their sound disabled the mice did not flee. The peacock butterfly then shows different defence strategies when discovered by different potential predators at different times throughout the year.
For more information about our lovely butterflies visit Butterfly Conservation you can join here and help them with their work. You may also like this article written by Richard Fox of Butterfly Conservation..Toughest butterfly on the block
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Besides my own experiences and observations:
Olofsson M et al (2012) ” Auditory defence in the peacock butterfly (Inachis io) against mice (Apodemus flavicollis and A. sylvaticus)” Behavioral Ecology and Sociobiology, p 209-215
Olofsson M et al (2013) “Eyespot display in the peacock butterfly triggers antipredator behaviors in naive adult fowl’, Behavioral Ecology V 24 p 305-310
Thomas J & Lewington R, (2010) ” The Butterflies of Britain and Ireland” British Wildlife Publishing, Milton on Stour, Gillingham, Dorset.
Villin A et al. (2005) “Crypsis versus intimidation-anti predation defence in three closely related butterflies” Behavioural Ecology and Sociobiology V 59, p 455-459
Villin A et al. (2005) “Prey survival by predator intimidation: an experimental study of peacock butterfly defence against blue tits” Proceedings of the Royal Society of London, Series B, Biological Sciences 272: 1203-1207.P
Photograph of ‘owl’ wings courtesy of Roy and Marie http://www.moorhen.me.uk with thanks