ZEBRA STRIPES: THEIR ROLE IN MODULATING BITING FLY LOADS AND BODY TEMPERATURE

Abstract

The function of zebra stripes is analyzed by testing two major theories – thermoregulation and protection from ectoparasites – on individual plains zebras and control species on Ol Pejeta Conservancy. This study significantly supports the thermoregulation theory: plains zebras exhibit a lower body surface temperature compared to control species. In fact, striped surfaces have reduced counts of flies compared to solid surfaces. Moreover, body surface temperature follows a normal curve pattern with time of day, peaking during hot afternoon hours and lowering with high wind speeds. Zebras were observed in the hot open habitats more often because their ability to stay cool for longer, confirming that they can regulate their temperature and heat loading. The ectoparasite hypothesis is analyzed by measuring the level of harassment and concentration of biting flies for its differences on solid versus striped colored coats. It is found that flies concentrate more on solid coats, specifically dark colors, and on smaller groups more than larger ones. Moreover, fly concentrations are highest on sunny hot days, bushier habitats, and low wind conditions. The zebras respond to increasing fly harassment by increasing tail swish and comfort movements.