Moths on tree trunks seek out more cryptic positions when their current crypticity is low

Abstract

Many animals use camouflage to avoid predation. Their crypticity, that is, the degree of a visual match between the animal's body and the background, affects their survival. Therefore, they may develop the ability to choose an appropriate background, which matches the animal's own colour pattern. We have previously shown that moths, Hypomecis roboraria, have the ability to increase their crypticity by repositioning their bodies from the initial landing position to the final, more cryptic, position. However, this repositioning behaviour is not always performed: some moths stay put on the initial landing position. We hypothesized that the moth's decision whether or not to reposition itself is related to its crypticity at the landing spot. We determined the crypticity from a detection task experiment, in which 'human foragers' searched for the moths in photos of moths at their landing spots. Moths that landed on the less cryptic positions were more likely to reposition themselves to the more cryptic positions. In contrast, moths that had already landed on substantially cryptic positions were less likely to reposition themselves. We suggest that the tactile cues received by moths from furrows and crevices, the elements of bark structure responsible for the colour pattern of the bark, may play a role in mediating this adaptive behaviour that results in improving the moths' visual crypticity. (C) 2013 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.