Zebra-like stripes on cattle deter biting flies, say researchers

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Example of the area of legs and body used to count biting flies on cows. Photo: Kojima et al. https://doi.org/10.1371/journal.pone.0223447

Black and white stripes on livestock such as cattle can prevent attacks from biting flies, research suggests.

A Japanese study team, writing in the open-access journal PLOS ONE, have described an experiment in which they painted zebra-like white stripes on several black cows to determine whether they repelled biting bugs.

They conducted insect counts, finding that the number of biting flies on the cows painted with white stripes were significantly lower than the numbers found on non-painted cows, and also lower than the numbers found on black cows painted with black stripes.

The black stripes were painted on the black cows to rule out the possibility that the odor of the lacquer paint was affecting the landing behavior of the flies.

Examples of experimental cows with or without painted stripes. (a) Black-and-white striped cattle with white lacquer, (b) Black-striped cattle with black lacquer, and (c) No stripe cattle. Kojima et al. https://doi.org/10.1371/journal.pone.0223447

Indeed, the zebra-like white stripes on cows were found to decrease the incidence of biting flies landing on individuals by 50%.

The researchers also found that fly-repelling behaviors in cows with the white stripes were lower than those in the non-painted and black-striped cows.

Tomoki Kojima and his colleagues concluded that painting black-and-white stripes on livestock such as cattle can prevent biting fly attacks.

It would, they said, potentially provide an alternative method of defending livestock against biting flies without using pesticides in animal production.

The study team did not set out to address the aged-old question of why zebras have stripes, but several researchers have similarly suggested the primary purpose is to repel biting insects.

However, others have suggested they play an important role in body temperature regulation, while some have proposed they are useful in confusing predators.

The researchers used six Japanese black cows for their experiment, comparing the effects of no paint, black stripes and white stripes on biting flies.

The fly-repelling behaviors monitored were head throwing, ear beating, leg stamping, skin twitching, and tail flicking.

Photographs of the right side of each cow were taken using a commercial digital camera after every observation and biting flies on the body and each leg were counted from the photo images.

Discussing their findings, the researchers noted biting flies are the most damaging arthropod pests of cattle worldwide, with an economic impact on United States cattle production estimated at more than $US2 billion a year.

Cattle owners have primarily used insecticides for control. However, insects often evolve resistance to a new pesticide within about a decade after its introduction.

“This work provides an alternative to the use of conventional pesticides for mitigating biting fly attacks on livestock that improves animal welfare and human health, in addition to helping resolve the problem of pesticide resistance in the environment.”

The study team was from a range of Japanese institutions.

Kojima T, Oishi K, Matsubara Y, Uchiyama Y, Fukushima Y, Aoki N, et al. (2019) Cows painted with zebra-like striping can avoid biting fly attack. PLoS ONE 14(10): e0223447. https://doi.org/10.1371/journal.pone.0223447

The study, published under a Creative Commons License, can be read here

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