Empirical tests of the role of disruptive coloration in reducing detectability - PubMed (original) (raw)

Empirical tests of the role of disruptive coloration in reducing detectability

Stewart Fraser et al. Proc Biol Sci. 2007.

Abstract

Disruptive patterning is a potentially universal camouflage technique that is thought to enhance concealment by rendering the detection of body shapes more difficult. In a recent series of field experiments, artificial moths with markings that extended to the edges of their 'wings' survived at higher rates than moths with the same edge patterns inwardly displaced. While this result seemingly indicates a benefit to obscuring edges, it is possible that the higher density markings of the inwardly displaced patterns concomitantly reduced their extent of background matching. Likewise, it has been suggested that the mealworm baits placed on the artificial moths could have created differential contrasts with different moth patterns. To address these concerns, we conducted controlled trials in which human subjects searched for computer-generated moth images presented against images of oak trees. Moths with edge-extended disruptive markings survived at higher rates, and took longer to find, than all other moth types, whether presented sequentially or simultaneously. However, moths with no edge markings and reduced interior pattern density survived better than their high-density counterparts, indicating that background matching may have played a so-far unrecognized role in the earlier experiments. Our disruptively patterned non-background-matching moths also had the lowest overall survivorship, indicating that disruptive coloration alone may not provide significant protection from predators. Collectively, our results provide independent support for the survival value of disruptive markings and demonstrate that there are common features in human and avian perception of camouflage.

PubMed Disclaimer

Figures

Figure 1

Figure 1

Examples of the five target types designed for this experiment. A different set of five targets were produced for each of the 15 oak trees photographed (and repeated when the tree images were rotated).

Figure 2

Figure 2

(a) Mean number of prey items attacked (from eight of each target type presented) per subject (_n_=81 in all cases) and (b) overall mean time to attack a detected prey per item, for each target type in the single target experiment (_n_=41, 40, 40, 39 and 40 subjects for target types 1–5, respectively). Error bars represent ±1 s.e.

Figure 3

Figure 3

(a) Mean number of prey items attacked (from 12 of each target type presented) per subject (_n_=24 in all cases) and (b) overall mean time to attack detected prey per item, for each target type in the multiple target experiment (_n_=24 in all cases). Error bars represent ±1 s.e.

References

    1. Allen J.A, Cooper J.M. Crypsis and masquerade. J. Biol. Educ. 1985;9:268–270.
    1. Beatty C.D, Bain R.S, Sherratt T.N. The evolution of aggregation in profitable and unprofitable prey. Anim. Behav. 2005;70:199–208. doi:10.1016/j.anbehav.2004.09.023 -DOI
    1. Behrens R.R. Bobolink Books; Dysart, IA: 2002. False colors: art, design and modern camouflage.
    1. Bond A.B, Kamil A.C. Visual predators select for crypticity and polymorphism in virtual prey. Nature. 2002;415:609–613. doi:10.1038/415609a -DOI -PubMed
    1. Bond A.B, Kamil A.C. Spatial heterogeneity, predator cognition, and the evolution of color polymorphism in virtual prey. Proc. Natl Acad. Sci. USA. 2006;103:3214–3219. doi:10.1073/pnas.0509963103 -DOI -PMC -PubMed

Publication types

MeSH terms

LinkOut - more resources