Size variability effects on visual detection are influenced by colour pattern and perceived size

A1 Originalartikel i en vetenskaplig tidskrift (referentgranskad)

Interna författare/redaktörer

Publikationens författare: Karpestam E, Merilaita S, Forsman A
Publiceringsår: 2018
Tidskrift: Animal Behaviour
Tidskriftsakronym: ANIM BEHAV
Volym: 143
Artikelns första sida, sidnummer: 131
Artikelns sista sida, sidnummer: 138
Antal sidor: 8
ISSN: 0003-3472


Most animals including humans use vision to detect, identify, evaluate and respond to potential prey items in complex environments. Theories predict that predators' visual search performance is better when targets are similar than when targets are dissimilar and require divided attention, and this may contribute to colour pattern polymorphism in prey. Most prey also vary in size, but how size variation influences detectability and search performance of predators that utilize polymorphic prey has received little attention. To evaluate the effect of size variability on prey detection we asked human subjects to search for images of black, grey and striped pygmy grasshoppers presented on computer screens in size-variable (large, medium and small) or in size-invariable (all medium) sequences (populations) against photographs of natural grasshopper habitat. Results showed that size variability either increased or reduced detection of medium-sized targets depending on colour morph. To evaluate whether bias in perceived size varies depending on colour pattern, subjects were asked to discriminate between two grasshopper images of identical size that were presented in pairs against a monochromatic background. Subjects more often incorrectly classified one of the two identical-sized targets as being larger than the other in colour-dimorphic than in monomorphic presentations. The distinctly patterned (striped) morph elicited stronger size perception biases than the dorsally grey or black morphs, and striped grasshoppers were incorrectly classified more often as smaller than grey grasshoppers. The direction of the effect of size variability on detection changed across colour patterns as the bias in perceived size increased. Such joint effects of variation in size and colour pattern on detection and perception can impact the outcome of behavioural and evolutionary interactions between visually oriented predators and their camouflaged prey. This may have consequences for population dynamics, evolution of polymorphisms, community species composition and ecosystem functioning. (C) 2018 The Association for the Study of Animal Behaviour.


colour pattern polymorphism, detection and perception, visual stimuli

Senast uppdaterad 2019-19-11 vid 04:15