Episode 308 – Plains Zebra: White Stripes

“…and today we’re talking about a fashion icon that is more interested in function over form. But more on that later.”

Few looks in nature are as iconic as a plains zebra’s stripes. But these savannah equines rarely think about fashion, so these stripes must have a function beyond their form. You may think you know what these patterns are for, so you might be surprised to know that there is an ongoing debate among researchers over their true purpose. We may never know for sure what secrets these zealous zebras hide, but it never hurts to try to uncover the mysteries of Life, Death, and Taxonomy. 

Description of the Plains Zebra

  • Classic horse look – tall lanky dog with rocks on its feet
  • Looks like a little stubby horse with black and white stripes
    • Short, buzz cut mane that has stripes that match the body

Measure Up

Welcome to the beloved Measure Up segment. The official listener’s favorite part of the show! The part of the show when we present the animal’s size and dimension in relatable terms through a quiz that’s fun for the whole family. It’s also the part of the show that’s introduced by you when you send in audio of yourself saying, singing, or chittering the words Measure Up into ldtaxonomy at gmail dot com. We do have a new Measure Up intro from Melissa!

Height

  • 127–140 cm (50–55 in)
  • How many zebras go into the height of a Senegalia senegal tree?
  • Hint: The Senegalia senegal is a source of gum arabic, which is used as an emulsifying agent in food products.
  • 8.7 zebras. A gum arabica tree is 40 feet tall.

Weight

  • 220–322 kg (485–710 lb)
  • How many Little Debbie Zebra Cakes would a zebra have to eat to eat its weight in Zebra Cakes?
  • Hint: Little Debbie Zebra Cakes are sponge cakes covered in vanilla cream with chocolate striped drizzle, not to be confused with zebra cake recipes that involve chocolate and vanilla cake mixed in a wave marble pattern.
  • 11,360 cakes. Zebra Cakes are a little more than an ounce.

Fast Facts about the Plains Zebra

Range: Eastern Southern Africa. From South Africa in the south to Kenya in the north to Mozambique in the east to Namibia to the west. Arid grasslands and woodlands.

Diet: Like a horse, they mostly eat grasses and sedges. Also eat bark, leaves, fruits, and roots.

Behavior: 

Plains zebras congregate in large groups made up of families with one dominant male (a stallion) and his harem of females (mares). The oldest females are the highest-ranking and the harems are nomadic, moving where the water is. These groups migrate to follow water and have been shown to travel over 300 miles – the longest in Africa.

Grevy’s zebra males establish static territories marked with dung. Any female that enters this zone is free game.

More dominant males will establish territories near watering holes to catch females with foals that need water more frequently. Less dominant males have to mark their territories away from watering holes. 

Males without females will gather into bachelor groups. They can survive up to a week without water. Males fight each other for females by biting and kicking each other.

Predated by lions, leopards, cheetahs, hyenas, crocodiles, and wild dogs. Bred with other equines to create hybrids called zebroids. Horses to create zorses, ponies to create zonies, and donkeys to create zonkies. 

These are usually sterile and deformed. Zebras can communicate with their usual whooping call but they also have other sounds as well as facial expressions using their lips and ears.

Major Fact: White Stripes

This BBC article by Yao-Hua Law was very helpful in finding the following information.

Why do zebras have stripes? You may have heard the most common answer, which is that it provides pattern disruption. Predators like lions look at a herd of zebras and find it difficult to tell where one zebra ends and the next begins, which is important for singling out prey.

However, it turns out that that is just one of many theories. There are at least 17 other proposed explanations with varying degrees of validity.

There are other examples of animals using grouping and pattern disruption to confuse predators like schooling fish. However, the theory is very difficult to test and there aren’t sufficient studies to show that lions have less success hunting zebras. We do know that lions eat zebras often.

Another theory is that the stripes confuse biting flies. The African savannah has several flies that like to hang around herds, some of which carry diseases like tsetse flies. In 2014, ecologist Tim Caro and his team tested the theory by studying herds of zebras and horses. They found that horse flies fed on the zebras less. They even found that horses dressed in stripes like zebras were bitten less. 

There were flies around, but they seemed to bounce off of zebras instead of landing for a bite. A possible explanation is that the stripes mess with their vision enough to prevent them from controlling their landing–perhaps disrupting depth perception. 

However, other researchers find it dubious that zebras would develop a defense against flies that would change their whole hair pattern, since flies are seasonal and regional–not a high priority threat on the savannah. Plus, other herding animals have no stripes and no serious problem with flies. 

Another, popular answer is thermoregulation. We know that black absorbs light and heat while white reflects them. Why have both?

Studies on striped water barrels didn’t show that the striped barrels were cooler. But it’s possible that the stripes work together with other zebra abilities. Like humans, horses and zebras sweat. The evaporation of sweat carries away a lot of excessive heat. However, water that is trapped in hair or fur insulates heat. 

Zebras have a protein called latherin that carries water to the end of their hairs where they can evaporate. Researchers, like Allison Cobb, found that black stripes are consistently warmer than white stripes. 

How does the temperature difference translate to cooling off? The study says, “we suggest that the abrupt temperature difference between the stripes causes chaotic air movement above the hair surface, thus enhancing evaporative heat dissipation.”

The stripes create a Dyson fan that causes sweat to evaporate.


Ending: So gather your females, kick your rival’s teeth in, and earn your stripes like the zebra here in LDT.