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1 july 2018

How did the zebra get his stripes? I seem to recall a visual gag from some movie featuring a black horse leaning up against a freshly-painted white picket fence and walking away a zebra. This is unlikely to have much evolutionary significance, though, even if I could find the clip on YouTube.

Rudyard Kipling, in the process of explaining "How the Leopard Got His Spots," offered an uncharacteristically prosaic explanation. At first monochrome, zebras moved, his narrator says, to

a great forest, 'sclusively full of trees and bushes and stripy, speckly, patchy-blatchy shadows, and there they hid: and after another long time, what with standing half in the shade and half out of it, and what with the slippery-slidy shadows of the trees falling on them, … the Zebra grew stripy.
I am not sure whether the Kipling explanation should be seen as Darwinian (camouflage as an adaptation to a shadowy habitat) or Lamarckian (dapple creatures with shadow and they breed dappled offspring). I am also not sure whether that's the right way to read Kipling. In any case, it's not far from various evolutionary rationales that have been attempted over the years. But scientists in the century since Kipling have made little progress on the problem.

Christopher Plumb and Samuel Shaw, in their new book Zebra for the Reaktion Animal series, describe ingenious measurements that prove that zebra stripes are useless as camouflage (148-50). It comes down to visual acuity. Predator species can't distinguish zebra stripes beyond a certain distance. From far away, zebras just look grey to them. If they are close enough to see the stripes, they're sure as damn close enough to see the zebra.

Zebra stripes are unlikely to scare predators away (in any case, they don't), and they are also not useful in managing sun exposure or helping zebras tell one another apart. The best current theory is that stripes help cut down on insect bites. Maybe that'll be the next mosquito repellent craze: zebra-stripe tattoos.

Plumb & Shaw offer many popular-culture takes on zebras, mostly from the design world, few from canonical poetry or art. Edward Lear's alphabet zebras are perhaps the best-known verbal ones. I searched my erratic memory for references to zebras in song, poetry, and prose, and came up nearly blank. The best I could think of was the title to one of Ross Macdonald's Lew Archer novels, The Zebra-Striped Hearse. If I remember correctly, that bizarre title is literal enough: a character in the book drives a zebra-striped hearse. Macdonald's novel, published in 1962, participates in a mod, often kitschy appropriation of zebra style that flourished at the time and has had intermittent revivals. Plumb and Shaw show that zebras have fascinated the "Global North" ever since word of them came back from the first colonizers of Africa. As a funky take on the commonest of sights – a psychedelic donkey – the zebra has long piqued Western fascination with the weird. George Stubbs' 1763 portrait of Queen Charlotte's zebra remains one of the few serious images, highly affecting and often-adapted. Stubbs immortalized this royal pet in a supremely dignified way, but the rough-and-tumble popular culture of Hanoverian England made the creature better known as "The Queen's Ass."

Zebra taxonomy is not too taxing, and Plumb & Shaw deal with it briskly. There are only three extant species of zebra. There is, however, a famous subspecies called the quagga that was well-known in the West even as it was being hunted to extinction in the 19th century. The last quagga died in 1883; photographs and other relics exist, and the natural history museum in Stockholm features a stuffed quagga fetus. Though genetically not far from the common plains zebra, the quagga was noted for its half-striped coat. Evidently researchers in South Africa have undertaken the project of bringing the quagga back to life. Not in some science-fictiony Jurassic way, but just by breeding some quagga-looking plains-zebra individuals till subsequent generations look more and more like quaggas. If nothing else, such a project demonstrates the similarities that Darwin noted between natural and artificial selection.

Can zebras be tamed? Individual ones have certainly become tractable in captivity. Attempts to domesticate them more generally have always failed, and aren't likely to experience any renaissance at this point. Plumb & Shaw print some fascinating images of Walter Rothschild, the 19th-century zebra aficionado who used to drive a one-zebra trap around his estate, and once nonchalantly drove up to Buckingham Palace in a four-in-hand, the four being three zebras and a pony. A surviving photo of the vehicle (104) obscures the pony, giving the impression that the carriage was pulled by four zebras. But in fact, the pony crucially played the role of lead animal (at the front left), and Rothschild's effort would have been futile without this arrangement. Rothschild was no charlatan, though; even he seemed to acknowledge that the feat was more stunt than milestone, and "his heart was in his mouth when Princess Alexandra tried to pat the leading zebra" (104).

With no prospect of becoming economically useful, the zebra has long meant, in the West, little aside from a decorative motif and a chance for a sport-hunting trophy. Yet there is something about their astonishing beauty that captivates the imagination. Stubbs caught it best in a formal profile view, perhaps, but photographer Marina Cano explains why when she says that "any angle is good" for imaging zebras (8).

Will the zebra survive? Mountain and Grévy's zebras are insecure, with about 9,000 of the former and 2,500 of the latter surviving in the wild when Plumb & Shaw went to press. Plains zebras still number about half a million, and seem secure in the Serengeti even if their range outside that great park is dwindling. But the quagga was a population of plains zebra, and its disappearance should make us less than confident of the survival of the whole species.

I am not sure I've ever seen a zebra outside a zoo. Horse fanciers tell me that they sometimes run across zebras on Texas ranches. It can't be a happy life for these exotics. They must miss their herds and their habitats, and they probably don't get on well with the mares and mules of the typical Texas turnout. But the appeal of zebras is such that even as their still-vast numbers shrink in the wild, people will keep them around as the ultimate pasture ornaments. This is both the good and the sad side of zebras' status as "charismatic megafauna" (11).

Plumb, Christopher, and Samuel Shaw. Zebra. London: Reaktion, 2018.