Caterpillar contortionists and bird poo masquerade

In one of nature’s quirkier developments, some species have found themselves resembling bird poo in their quest for survival. It makes sense. Remaining motionless on plants, casually looking like something hardly any animal is likely to find appetising. If you can pull off the poo-resembling colours and patterns, you stand a good chance.

It is an anti-predator defence known as masquerade – resembling something inedible or uninteresting, being spotted but ignored. Bola spiders are famous for their bird dropping disguise, but some moth caterpillars resemble poo too. For the caterpillars, body posture may be just as important as their unpleasant-looking appearance.

Using replica models, researchers from Japan have demonstrated how contorting their bodies to more closely resemble an unwanted avian dollop decreases the caterpillar’s likelihood of being identified and picked off by predators. In contrast, if stretched out straight, the caterpillars’ markings alone were often not quite enough to fool its hunters. Plain green caterpillars fared poorly no differently regardless of their posture, suggesting that a combination of markings and body shape is key to improving the bird poo masquerade.

Suzuki, T & Sakurai, R. (2015) Bent posture improves the protective value of bird dropping masquerading by caterpillars. Animal Behaviour, 105, 79-84. doi: 10.1016/j.anbehav.2015.04.009

Image credits: http://baba-insects.blogspot.co.uk/2015/05/blog-post_20.html and http://blog.yohbo.main.jp/

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