Natures Barcode: Exploring the Purpose of Zebra Stripes
General Jan Kemp’s 1936 quip describing mountain zebras as “donkeys in football jerseys” might have been a bit blunt, but it was not far from the truth. Zebras, with their distinct black and white stripes, are a standout amongst both their equine kin and the array of large herbivores with which they share their grazing territories. Across all four zebra species, these eye-catching stripes are a prominent feature. This has sparked considerable debate and numerous inventive hypotheses regarding their purpose.
One popular theory suggests that zebra stripes aid in regulating body temperature. It’s hypothesized that the contrasting black and white stripes might create air currents that help dissipate heat, or zebras could manage heat exchange with their environment by channeling blood to either the black or white stripes. However, this theory lacks direct empirical evidence. Additionally, other large, non-striped grazers thrive in hot climates just as effectively, suggesting that stripes aren’t essential for managing body heat.
A Defense Against Blood-Sucking Flies
Another intriguing theory is that zebra stripes might deter blood-sucking tsetse flies, which typically use vision to locate hosts and are drawn to large, uniform color patches. Research shows that zebras suffer fewer bites from tsetse flies compared to other large grazers. Experiments have also demonstrated that striped models attract fewer tsetse flies than models painted in solid black, white, or grey. However, this theory isn’t without its contradictions. Tsetse flies predominantly inhabit woodlands, whereas zebras are primarily found in open grasslands. Moreover, zebras living outside tsetse fly zones sport the same stripes as those within these areas.
Camouflage or Confusion for Predators?
The camouflage hypothesis suggests that zebra stripes might help to obscure their outline. However, this seems unlikely given zebras’ active nature, their tendency to dwell in open spaces, and their lack of a freeze response to danger, all of which are atypical for camouflaged animals. Some speculate that the stripes could confuse predators by making it difficult to single out an individual in a herd or by distorting perception, leading to miscalculations in predator attacks. Despite this, predators like lions, hyenas, and cheetahs successfully hunt zebras, suggesting that any potential confusion or perception distortion caused by the stripes is limited.
The Social and Antipredator Function of Stripes
A crucial insight into the purpose of zebra stripes lies in their impact on zebras themselves. The striking contrast of the stripes is visually stimulating, and zebras seem drawn to this pattern, even approaching artificially painted black-and-white panels. This preference for stripes may be linked to their antipredator strategies. When under threat, zebras cluster tightly, with the stallion at the rear. Their safety hinges on cohesive group movement, especially at night or in dust-clouded conditions where visibility is low. Here, the sharp contrast of black and white stripes becomes an asset, enhancing visibility among the herd members. This feature is unique to zebras, the only large herbivores known to maintain such tight formations during predator attacks.
While the exact purpose of zebra stripes remains a subject of debate, their role in enhancing visibility within the herd, especially in low-light and chaotic situations, is a compelling aspect of their unique adaptation.
