Zebras, with their distinctive black and white striped coats, are among the most recognizable animals. This iconic pattern has long captivated human curiosity, leading to questions about their true coloration and its purpose. While the image of a black and white zebra is deeply ingrained, their biology reveals a more intricate picture.
Beyond the Classic Stripes
While the classic black and white pattern is characteristic of most zebras, variations in their striping and coloration do exist. These deviations are rare and often result from genetic anomalies or subspecies-specific traits. For instance, “golden” or “blonde” zebras exhibit a form of leucism, a condition involving a partial loss of pigmentation, which results in their typically black stripes appearing golden or cream-colored.
Another rare occurrence is melanistic zebras, which appear darker than usual, sometimes almost entirely black with faint stripes. This condition involves an increased concentration of dark pigment. Conversely, some plains zebra subspecies, such as Chapman’s zebra, can display brownish “shadow” stripes between their prominent black stripes, and foals may be born with brown stripes that can sometimes persist into adulthood. These variations, though uncommon, highlight the genetic diversity within zebra populations and offer a glimpse into the complexities of their coat patterns.
The Zebra’s True Skin Color
Beneath their striking striped fur, a zebra’s skin is uniformly dark, typically black. The stripes are a result of how pigment is deposited in their hair follicles, not the underlying skin coloration. Melanocytes, the cells responsible for producing melanin, determine hair color.
In zebras, white stripes form where melanin production is suppressed in the hair follicles, meaning the white hair lacks pigment. This contrasts with black hair, which grows from follicles where melanin is actively produced. Therefore, the zebra’s base color is considered black, with white stripes developing due to the absence of pigment.
Why Zebras Have Stripes
The purpose of zebra stripes has been a long-standing scientific inquiry, with several leading hypotheses attempting to explain their evolutionary advantage. One prominent theory suggests that stripes deter biting flies, such as horse flies, which can transmit diseases lethal to equids. Research indicates that the high contrast of the stripes confuses flies, making it difficult for them to land on the zebra’s body. Studies have shown flies are less likely to land on striped surfaces compared to solid-colored ones.
Another hypothesis proposes that stripes play a role in thermoregulation, helping zebras manage their body temperature in hot climates. The black stripes absorb more sunlight and become hotter than the white stripes, potentially creating small convection currents that cool the animal’s skin. This temperature difference, observed between the black and white stripes, can reach 12-15°C during the day. Zebras also possess a protein called latherin, which facilitates evaporative cooling through sweating, a process potentially aided by the air movements generated by the stripes.
Furthermore, stripes may offer a form of camouflage, particularly through disruptive coloration, making it harder for predators to single out an individual within a moving herd. While some studies suggest this effect is limited at longer distances, the “motion dazzle” effect can confuse predators when zebras are grouped closely. Finally, the unique stripe pattern of each zebra, akin to a human fingerprint, is thought to aid in social recognition, helping individuals identify each other within a herd, especially between mothers and their foals.