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Avoiding detection: effects of prey pattern regularity, background matching and complexity of the habitat background
Stockholm University, Faculty of Science, Department of Zoology, Department of Animal Ecology.
Stockholm University, Faculty of Science, Department of Zoology, Department of Animal Ecology.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this study we test how aspects of prey colour pattern regularity affect crypsis and how visual complexity of the background affects prey detection. We performed two predation experiments with artificial prey and backgrounds, using blue tits (Cyanistes caeruleus) as predators. In the first experiment we found that a prey pattern consisting of variable element shapes did not compensate for mismatching pattern elements, because a variable pattern with some mismatching element shapes was easier to detect than a variable pattern with background-matching element shapes only. Contrary to a previous hypothesis, a pattern with regular, background-matching element shapes was not easier to detect than the pattern with variable, background-matching shapes. All prey types were easier to detect on a simple than on a complex background with more diverse and complex element shapes. In the second experiment we used prey pattern consisting of invariable, background-matching elements and tested how spatial regularity of the elements affects crypsis. We found that on a complex background the spatially irregular prey with randomly placed pattern elements was more difficult to detect than the regular prey with all elements aligned, but on a simple background both prey types were equally easy to detect. Here background complexity was due to element shape complexity only. In conclusion, our study shows that spatial regularity of prey pattern but not regularity due to invariable pattern element shapes deteriorates crypsis. Visually complex habitat backgrounds and specifically those consisting of elements with complex shapes make detection of cryptic prey difficult.

National Category
Ecology
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:su:diva-30544OAI: oai:DiVA.org:su-30544DiVA: diva2:272845
Available from: 2009-10-18 Created: 2009-10-18 Last updated: 2010-01-14Bibliographically 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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