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Prey concealment: visual background complexity and prey contrast distribution
Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
2010 (English)In: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 21, no 1, 176-181 p.Article in journal (Refereed) Published
Abstract [en]

A prey may achieve camouflage through background matching and through disruptive coloration. Background matching is based on visual similarity between the prey and its background, whereas disruptive coloration emphasizes the use of highly contrasting pattern elements at the body outline to break up the body shape of the prey. Another factor that may influence prey detection, but has been little studied, is the appearance of the visual characteristics of the background. We taught blue tits (Cyanistes caeruleus) to search for artificial prey and manipulated the appearance of the prey and the background. We studied the effect of diversity of shapes in the background on prey detection time. We also studied the differing predictions from background matching and disruptive coloration with respect to contrast level and location of high-contrast elements in prey patterning. We found that visual background complexity did indeed increase prey detection time. We did not find differences in detection time among prey types. Hence, detection time was not affected by contrast within prey patterning, or whether the prey patterning matched only a sub-sample or all the shades present in the background. Also, we found no effect of the spatial distribution of shades (highest contrast placed marginally or centrally) on detection times. We conclude that background complexity is important for the evolution of prey coloration. We suggest that it may facilitate concealment and favor the evolution of camouflage over warning coloration. Preference for visually complex backgrounds might provide prey with a so far untested means to decrease predation risk.

Place, publisher, year, edition, pages
2010. Vol. 21, no 1, 176-181 p.
Keyword [en]
predation; crypsis; camouflage; background matching; disruptive coloration; aposematism
National Category
Ecology
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:su:diva-30547DOI: 10.1093/beheco/arp174ISI: 000272925000025OAI: oai:DiVA.org:su-30547DiVA: diva2:272847
Available from: 2009-11-30 Created: 2009-10-18 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Life at stake when playing hide and seek: Concealing effects of prey colouration and visual backgrounds
Open this publication in new window or tab >>Life at stake when playing hide and seek: Concealing effects of prey colouration and visual backgrounds
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A prey animal can use different strategies to avoid becoming eaten by predators. One such widely recognised strategy is the use of body colouration to decrease the risk of becoming detected, i.e. cryptic colouration. The principles of crypsis that I have studied are background matching, disruptive colouration and distractive markings. Further, I also studied the concealing effect of the visual background habitats. I used artificial prey items and backgrounds, and blue tits (Cyanistes caeruleus) as predators, to investigate prey concealment. In Paper I, I tested if high-contrast markings in prey coloration or in the background would result in a distracting effect. I found that such markings did increase prey search time, even when the prey markings were lighter or darker than the background. In Paper II, I studied the use of chromatic cues by predators when searching for prey. The birds easily detected prey that chromatically deviated from its background. Interestingly, background-matching prey was more difficult to detect when the colour scheme had low ultraviolet and high shortwave reflectance compared to when the reflectance bands were even. In Paper III, I studied optimisation of achromatic contrast within prey colour pattern and also the effect of shape diversity of background pattern elements on prey detection. I found that all prey types were more difficult to detect on the diverse background, but the level of contrast within prey pattern did not influence search times. In Paper IV, I further investigated how a prey should optimise its patterning with respect to background matching. I found that prey with repeated pattern elements was equally hard to detect as prey with more variable pattern. However, prey with a spatially regular pattern (aligned pattern elements) was easier to detect than prey with a spatially irregular pattern. In this paper I also found that high complexity of element shapes in the background, made the search task more difficult.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2009. 34 p.
Keyword
predation; adaptive prey coloration; camouflage; concealment; crypsis; background matching; disruptive colouration; distractive markings
National Category
Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-30548 (URN)978-91-7155-959-3 (ISBN)
Public defence
2009-11-20, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2: AcceptedAvailable from: 2009-10-28 Created: 2009-10-18 Last updated: 2009-10-22Bibliographically approved

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