Dazzle coloration and prey movement

Abstract

Many traits in animals reduce the rate of attack from visually hunting predators, including camouflage, warning signals and mimicry. In addition, some animal markings may reduce the likelihood that an attack ends in successful capture. These might include dazzle markings, high-contrast patterns that make the estimation of speed and trajectory difficult. However, until now, no study has experimentally tested whether some markings may achieve such an effect. We developed a computer 'game' where human 'predators' have to capture computer-generated prey moving across a background. In two experiments, we find that although uniform camouflaged targets were among the hardest to capture, so were a range of high-contrast conspicuous patterns, such as bands and zigzags. Prey were also more difficult to capture against more heterogeneous than uniform backgrounds, and at faster speeds of movement. As such, we find the first experimental evidence that conspicuous patterns, similar to those found in a wide range of real animals, make the capture of moving prey more challenging. Various anti-predator markings may work prey during motion, and some animals may combine such dazzle patterns with other functions, such as camouflage, thermoregulation, sexual and warning signals.

Paradox lost: variable colour-pattern geometry is associated with differences in movement in aposematic frogs

“…This pattern-movement combination might create the illusion of a static pattern or a pattern with a greatly reduced speed that affects predators' abilities to track the trajectory of moving individuals and predict their attack angle [11,14]. This may be more pronounced when movements occur at a higher speed [22,23] and over longer segments [15], as in these frogs. Frogs moving randomly, with unpredictable changes of direction, have more interrupted patterns and move at a lower average speed, over shorter segments than directional frogs.…”

Tracking objects that move where they are headed

“…After all, players of ball sports, such as basketball and football, sometimes will deliberately face in a direction different from where they expect to catch or throw the ball, a strategy that seems to successfully confuse novices (Sebanz & Shiffrar, 2009). Animals also benefit from surface properties, such as highcontrast markings, that mislead the motion perception of predators (Stevens, 2007;Troscianko, Benton, Lovell, Tolhurst, & Pizlo, 2009) and can even hinder human predators (Stevens, Yule, & Ruxton, 2008). Similar tactics were used by military to camouflage navy ships during World War I, so that enemies would not know the direction or speed of the ships (Behrens, 1999).…”

The function of zebra stripes

“…Functional hypotheses fall into five broad categories: a form of crypsis probably matching a woodland background, disrupting predatory attack, reducing thermal load, having a social function and avoiding ectoparasite attack [5][6][7] . Only two have received more than passing attention: humans find moving striped objects difficult to target accurately on a computer screen, suggesting a possible motion dazzle confusion effect [8][9][10] , and tsetse flies, stomoxys stable flies and tabanid biting flies are less likely to land on black and white striped than on uniform surfaces [11][12][13][14] .…”

“…To investigate an antipredator function that subsumes several mechanisms including crypsis 3 , disruptive colouration of the body's outline 17 , increased apparent size 18 , making individuals difficult to single out in a herd 19 , confusing a predator in some way 6,9 or advertising flight ability 20 , we examine (ii) whether striping in equids is associated with the presence of sympatric large predators: spotted hyaena (Crocuta crocuta), lion (Panthera leo), tiger (P. tigris) and wolf (Canis lupus). (iii) To explore heat management 6 , we examine associations between striping and living in habitats with average maximum annual temperatures of 25°C through to 30°C.…”