Disruptive Colouration

This week I am discussing disruptive colouration as a means of camouflage. Disruptive colouration is when an organism uses contrasting markings to break up the outline of their body against its background (Skelhorn & Rowe, 2016). This method is used by prey, to increase the chances of survival, but it is also used by predator to increase the likelihood of getting a meal (Merilaita & Lind, 2005).  

Cuthill et al. (2006) describes three types of disruptive colouration. The first one being differential blending, which is when patches in the pattern of the organism match the background, be it colour or texture. The second type is maximum disruptive contrast, where flanking pattern colours are often highly contrasting, creating a confusion effect. Lastly, having markings at the edge of the organism’s body helps it blend in with their background (Cuthill et al., 2006).

Unlike background matching, disruptive colouration is said to be one of the least researched methods of camouflage (Stevens & Merilaita, 2008). It includes a wide variety of animals including; mammals, fish, reptiles and birds. Stevens and Merilaita (2008) believe that even though it has been suggested that disruptive colouration is used for camouflage or confusion of prey or predator there needs to be additional research into the field to be conclusive.  

I have always believed that zebras have stripes for protection against predators. As using maximum disruptive contrast when they are in a herd seems logical to me. I image a pride of lions sneaking up on the herd of zebras. As they approach, and the zebras become aware of their predators and chaos ensues.  Hundreds of zebras running away and meanwhile, their colouration protecting them as the lions are confused by where one zebra begins and another ends.

However, Melin et al. (2016) disagree with this theory. What betrays humans is not always the same for other organisms, this is to do with the way different organisms see (Cuthill et al., 2005). This is the bases of Melin et al. (2016) study, which suggests that zebras do not have advantages over other animals that are not striped because the zebras prey isn't as fooled as human eyes. In fact, the study concludes by suggesting that perhaps the stripes are for avoidance of the parasitic tabanid biting fly (Melin et al., 2016). This is only a recent study and one of the first to suggest that zebras pattern isn't to do with disruptive colouration. 

Next week I will be giving you some examples of disruptive colouration and how they relate to their environments. As for now, I will leave you with some photos of zebras that I think look a lot like disruptive colouration. 

Zebras in a herd  

Zebras in bushes 

References

Skelhorn J., & Rowe C. (2016). Cognition and the Evolution of Camouflage. Proceedings of the Royal Society of London B. 283(1825), 20152890.

Cuthill I., Stevens M., Sheppard J., Maddocks T., Pa´rraga C., & Troscianko T. (2005). Disruptive Coloration and Background Pattern Matching.Nature. 434(7029), 72–74.

Cuthill I., Stevens M., Windsor A., & Walker H. (2006). The Effects of Pattern Symmetry on Detection of Disruptive and Background-matching Coloration. Behavioural Ecology. 17(5),828-832. 

Melin A., Kline D., Hiramatsu C., & Caro T. (2016). Zebra Stripes Through the Eyes of Their Predators, Zebras and Humans. PLOSone. 11(1), 1-18.

Merilaita S., & Lind J. (2005). Background-Matching and Disruptive Coloration, and the Evolution of Cryptic Coloration. Proceedings of the Royal Society of London B. 272, 665–670.

Stevens M., & Merilaita S. (2008). Defining Disruptive Coloration and Distinguishing its Functions. Proceedings of the Royal Society of London B. 364(1516), 481-488.