Spotty cows avoid horsefly bites

"Fjällko" Photo: Susanne Åkesson

A warm summer day the air is full of insects, such as pollinators, butterflies and blood sucking dipterans. Tabanid flies (or horse files) can in many areas be an annoying pest to grazing horses and cattle. The horse flies bite to suck blood from the mammalian host and use the blood meal to produce eggs. These eggs are later attached to vegetation near to water and ponds, in which the larvae develop. The tabanid flies can see reflected linearly polarized light and use this information to locate water and mammalian hosts. In a recent paper published in PLoS ONE we demonstrate that the coat pattern of cattle is crucial in attracting the biting flies, such that the more spots you have the less attractive you are. Cattle have been bread to increase meat and milk production, with limited focus on coat pattern appearance. However, for the future we suggest that also this feature should be considered in cattle farming in order to minimize spread of diseases to cattle and to minimize disturbance during grazing. It is interesting to note the typical coat pattern of the ancient Swedish cow race “fjällko” (photo above), which seem to have an ideal coat pattern in order to avoid horsefly bites – predominantly white with black spots.  

Susanne