The striking black and white patterns of zebras often prompt a common question: are these iconic animals black with white stripes, or white with black stripes? Understanding their coloration reveals insights into their biology and the evolutionary purposes behind their distinctive appearance.
The Truth About Zebra Stripes
Zebras possess dark skin underneath their fur. Their stripes result from specialized cells called melanocytes, which produce pigment in hair follicles. In black stripe areas, melanocytes are active, producing melanin, while in white stripe areas, these cells are deactivated and do not produce pigment. This selective activation and deactivation during embryonic development determines the striped pattern. Therefore, because black is due to pigment presence and white to its absence, zebras are generally considered black animals with white stripes.
Why Zebras Have Stripes
The evolutionary purpose of zebra stripes has been a subject of scientific inquiry for centuries. One prominent theory suggests that stripes deter biting insects like tsetse flies and horseflies. Studies indicate that these insects are less likely to land on striped surfaces, possibly due to visual confusion or interference with polarized light perception. This protection is particularly important as these insects can transmit diseases harmful to zebras.
Another theory proposes that stripes play a role in thermoregulation, helping zebras manage their body temperature in hot environments. Black stripes absorb more heat, while white stripes reflect it, potentially creating small convection currents that cool the animal’s body. Research has also indicated that zebras might possess an ability to raise the hairs on their black stripes, which could further aid in heat transfer away from the skin.
Though often considered camouflage, the effectiveness of stripes for concealment from predators is debated. Some suggest a “motion dazzle” effect, where a herd’s stripes create a confusing, indistinct mass, making it difficult for predators to single out an individual. However, studies indicate predators like lions and hyenas may not clearly discern stripes beyond certain distances, especially at night or twilight when hunting occurs. This suggests camouflage may not be the primary function.
Stripes also serve a social function, enabling individual recognition within a herd. Each zebra’s stripe pattern is unique, much like a human fingerprint. This distinctiveness helps zebras identify one another, which is particularly useful for mothers and their foals.
Stripe Variations and Uniqueness
No two zebras share an identical stripe pattern, which varies across species. The three main species exhibit distinct characteristics.
Grévy’s Zebras
Grévy’s zebras, the largest species, display narrow, closely spaced stripes that do not extend to their white bellies. They also have large, rounded ears.
Plains Zebras
Plains zebras, the most common, have broader stripes vertical on their bodies but horizontal on their hindquarters. Some populations feature fainter “shadow” stripes.
Mountain Zebras
Mountain zebras have thinner, more closely spaced vertical stripes on their necks and torsos, transitioning to wider horizontal bars on their haunches and fine horizontal bands on their legs. A distinguishing feature is a unique grid-iron pattern on their rump and often a dewlap, a flap of skin under the chin.
The development of these varied stripe patterns is influenced by genetic and environmental factors.