Avoiding attack: Design and Deception in Nature at next MVFN lecture
by Cathy Keddy
The Mississippi Valley Field Naturalists’ (MVFN) public lecture series, Trends in Fauna and Flora, continues October 20 with the second presentation, “Avoiding Attack: Design and Deception in Nature” with guest speaker Dr. Tom Sherratt from Carleton University. You do not need to be an expert to enjoy these presentations—just possess a curiosity or appreciation for wild nature. Cottagers, hunters, fishermen, canoeists, hikers, campers, artists and seasoned field naturalists alike will find something to interest them as we explore what lives in Lanark County and how best to protect it for future generations. Refreshments are offered at each lecture.
Dr. Sherratt will talk about crypsis (camouflage), warning signals and mimicry in nature—a diverse array of mechanisms that many organisms have evolved to avoid attacks from predators. He has studied these interesting and effective survival strategies in many different species including birds, butterflies, fungi, and dragonflies, and has also published a book on the subject.
Do you remember learning about peppered moths in England in connection with the Industrial Revolution and how the dark form of the moth became more abundant than the peppered (black and white) form because it could hide on soot-covered tree trunks? Well, this is only part of the cryptic story for these moths…It turns out that the peppered form is hidden from birds (which can see ultraviolet light) when resting on crustose lichens (both moth and lichen reflect UV light), but not when resting on foliose lichens (these lichens do not reflect UV light but the moth does). To us however, being unable to detect UV light, the moths appear camouflaged on both lichen types!
Mimicry in nature seems unlimited. Flies pretending they are bees—done so well, even professional entomologists may file specimens in the wrong drawer. Or consider sexual mimicry in damselflies—30-90% of females (in some species) want the males to think they too are males to avoid harassment. There are moth larvae that look like twigs and moths that look like leaves. Some moths even look like bird droppings. An example is the aptly named ‘bird-dropping moth.’ Mimicry comes in many forms including shape, odour, taste, sex, sound, movement, or colour. All reflect the ability of predators to perceive and prey to deceive.
Why are warning signal colours in nature (in our eyes) yellow and black? Why not red and blue? Why don’t more prey species sport these colours? Rather than wonder why a particular organism does not seem to be wearing warning colours, or does not appear to be cryptic or be using mimicry, we should consider first what sorts of predators the organism is at most risk from, and then think about that predator’s sense perceptions. Also remember… our appreciation of predator-prey communication is hampered by our own limited sensory perceptions of nature.
In the fascinating natural world, just as in our society, there is likely far more deception than we realize. Dr. Sherratt will tell us more at his MVFN presentation “Avoiding Attack: Design and Deception in Nature,” at 7:30 pm, Thursday, October 20, 2011 at the Almonte United Church, 106 Elgin St., Almonte. All are welcome ($5 fee for non-members). For further information please contact MVFN’s Program Chair Cathy Keddy at 613-257-3089.