Friday, 16 November 2012

Patterns and Messages

What is the message conveyed in what we see in nature. When I look at the endless array of patterns displayed in moth wings, I wonder about the messages that are meant and interpreted by the observers. These "observers" are mostly vertebrate predators like birds and lizards.

In the 1960’s the noted Smithsonian photographer Kjell Sandved had fanciful interpretations of butterfly wings. His calendars were very popular at the time. I’m sure he would concede that his interpretations of butterfly wings were not really what nature had intended! But it does beg the question of messages and interpretation.

On the light sheet, all bets are off. Every species is present on an equal basis. camouflage, odd resting postures all mean nothing or very little to potential predators. It’s instructive to observe which creatures (mostly moths are used here) are taken and which are not. Birds find the light sheet opportune for easy pickings but the insect-eating marsupial Antechinus and lizards (mostly geckos) can often be seen harvesting the bounty.

The hungry vertebrates are not influenced by patterns on the moth wings as they view them on the light sheet—or are they. Those moths that would be camouflaged on trees or leaves are the ones that are taken first. More brightly coloured and non-camouflaged species are left alone. They are there all day. I’ve never seen a bird attempt to eat one of these moths. Whatever it is that influences their judgement, it is fairly well fixed and these creatures are left alone (avoided?). [My mothologist friend, the word merchant, is very careful about the use of words in our interpretation of natural observations].

Two moths that are not eaten by birds and lizards
This arctiid is also left alone by birds but the Green Tree Ants have no problems tearing it to shreads
 But it is not just bright colours that matter. The moth above, one of the aquatic pyaloids, is brightly coloured but is avidly eaten by the birds that visit the light sheet in the morning. Perhaps, it is some sort of pattern recognition that is at play here.

Patterns and postures are probably genetically set and learned by birds and lizards early in their lives. They seem to know what to avoid and what to try. Colours play a big role. In many groups there are mimics that are edible but possess patterns that resemble the distasteful ones. As long as their numbers are lower than those of the "models" their protection is assured. I have not observed this situation with respect to the moths above.

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