Nothing in nature is random. The characteristics of the fur and skin of animals, in which humans can find an aesthetic sense, usually have an evolutionary utility. Peacocks flap their colorful wings to attract the attention of the opposite sex in breeding, for example. Other animals have spots or stripes to camouflage themselves from their predators, as a temperature regulation or as a social relationship strategy.
In the case of zebra stripes, it was not so clear. Its origin was still enigmatic until last year: a study published by the journal PLOS ONE on February 20, 2019 takes us a step further in answering this puzzling question: zebras have stripes to avoid parasites that suck the blood.
Researchers from the University of Bristol and UC Davis, in California, were responsible for solving this question, which had been unfinished for 150 years, investigating the behaviors of tabid flies around zebras and domestic horses in a livery in North Somerset, using techniques of video analysis.
The conclusions of the study show that, although the stripes do not deter flies from a distance , because both zebras and domestic horses experience the same rate of circles as flies, but they do so in short distances. Zebras and horses had different landing times, analysis of the videos revealed.
According to Dr. Martin How, a researcher at the Royal Society University in the Faculty of Biological Sciences: “This reduced ability to land in the shelter of the zebra may be due to the fact that the stripes interrupt the visual system of the flies in their last moments of approach. ”.
That is, the stripes have the function of dazzling the flies in some way once they are close enough to see them with their eyes, in low resolution.
The second step was to observe the behavior of the horse flies around the same horses with cloth coats of different colors: black, white or zebra striped. A key experiment to elucidate if stripes are responsible for this, since it would exclude any differences in behavior or smell between horses and zebras.
As before, when the horses wore coats with striped patterns, the flies made fewer landings compared to when they wore single-colored coats.
The research also looked at the behavior of the zebra and horse in response to stinging flying insects. Zebras exhibited preventative behavior , such as running away and wagging their tails at a much higher rate than horses. Consequently, the few flies that eventually landed successfully on zebras spent less time on their back compared to those that landed on horses, and very few stayed long enough to perform a blood test.
In Africa, where zebras are native, flies can carry debilitating and dangerous diseases, such as trypanosomiasis and African horse sickness, which cause wasting and often death. Therefore, it is not surprising that zebras use both behavioral defense and morphological lines to avoid horse flies.
Flies are a widespread problem for domestic animals anywhere in the world, so mitigation techniques derived from this revealing research, such as the development of anti-fly clothing designed to resemble zebra stripes, could spell a revolution. interesting for the health and welfare of animals.
Reference: ‘Benefits of zebra stripes: Behavior of tabanid flies around zebras and horses’ by Tim Caro, Martin How et al in PLOS ONE.
Image credit: iStock Photo.
