Striped horses of the Serengeti

The two most abundant herbivores we saw in the Serengeti in March were Plains Zebras and Topis. The Plains Zebra is also called Burchell’s Zebra. These are the strange striped wild horses of Africa. There are three species of zebra in Africa, the Burchell’s or Plains Zebra, Grevy’s Zebra and the Mountain Zebra. The zebra’s stripes are an enigma in the savanna. For years, scientists have debated the evolutionary reason behind a zebra’s stripes. There is a reason for everything in nature so the first obvious question is why the zebra has such visible stripes in the bush veld where camouflage would be a evolutionary advantage in an environment seething with predators.

“These strange striped horses are caught in a permanent dance of  conflict and survival. Waves of zebras are caught in a desperate never ending race for survival. They trace ancient paths forming a delicate lacework in the sand, creating patterns in the grass.”

~Dereck Joubert

Zebras are nomads and follow the rain which leads to fresh new grass. Zebras have a characteristic neighing which has become an iconic sound on the plains and can be heard day and night. The next image was taken on our first afternoon out while watching a pair of the lions mating. The passing zebra were aware of the lions and gave them a wide berth.

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Zebras stay in family groups within a bigger herd. They walk in strict hierarchy. Only the stallion can walk along the line. The zebras move in herds because they provide more eyes to watch for predators.

“We are the products of editing, rather than of authorship.”
~ George Wald

The riddle of the”painted horses'” stripes is progressively being decoded. One reason offered for their stripes is that in a herd, the stripes have a blinding effect on predators making it difficult for them to pick out a target in the blur of stripes. Other reasons have been offered:- 

In a fascinating article by National Geographic, Dell’Amore explains that the “stripe riddle” has puzzled scientists, including Darwin, for over a century. There are five main hypotheses why zebras have the stripes: to repel insects, to provide camouflage through some optical illusion, to confuse predators, to reduce body temperature, or to help the animals recognise each other. New analysis of the Plains Zebra show that temperature is the factor most strongly linked to striping: More specifically, the warmer it is, the more stripes on the zebra.

In a project supported by National Geographic Society’s Committee for Research and Exploration, Brenda Larison, a biologist at the University of California, together with colleagues , visited 16 zebra populations throughout Africa and studied their stripe patterns. They measured 29 different environmental factors – such as soil moisture, rainfall, prevalence of disease-carrying tsetse flies, and distribution of lions – looking for correlations to the stripe patterns across the zebra’s range. The two factors most correlated with the stripes were consistent temperature in a particular area and the average temperature during the coldest part of the year. Why temperature affects the number of stripes is another matter. One possible reason is that the black and white stripes absorb temperature at different rates creating micro eddies which provide a moderate cooling effect.

“Man masters nature not by force but by understanding. This is why science has succeeded where magic failed: because it has looked for no spell to cast on nature.”
~
Jacob Bronowski

Another idea suggests that more stripes may be a barrier against disease, since disease-carrying biting flies, like horseflies, tend to like it hot. Experiments in the field have shown that biting flies don’t like landing on striped surfaces. While it gets warm in the Serengeti, rising to the early thirties centigrade, it does not get fiendishly hot, into the upper forties.

One stallion was walking with the group in the previous image, but must have got the scent of the mating lions on the wind. He stopped to get a good look to see exactly where and how many there were. These herds of zebra are usually the first to enter new grazing pastures. They trample down the long vegetation so the gazelle and wildebeest can follow.

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We only saw one real fight among the thousands of zebra we saw. The fights are usually among males. They usually try to bite each other’s fetlocks or flanks. These two stallions decided to have a full on fight.

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This fight was serious with one stallion going for the other’s neck, with intent.

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What was more surprising was this fight went on for what seemed to be more than ten minutes. There was obviously a serious issue which had to be sorted out.

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Further research by Professor Tim Caro, from the University of California, found that stripe visibility decreases dramatically as light falls. At dusk, when hunting by carnivores normally begins, humans can resolve stripes from greater distances than other mammals: 3 times those of lions, 5 times further than spotted hyenas, and 1.9 times more distant than zebras.

“It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change.”
~
Attributed to Charles Darwin

This next image is of a small family group where one mare had a nasty gash on her shoulder from what must have been a lion attack. Hyaenas normally attack the rump. She obviously managed to get away. With luck it will not get infected and will heal, but zebra cannot lick their wounds clean, as they do not have the flexibility of cats. Zebras do tend to stand head to tail so each can use the other’s tail as a fly swat.

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Births are usually timed to match the abundance of the new grass. Serengeti’s volcanic grasslands respond quickly to rain.  The new born foal imprints on the mother’s pattern from birth and its mother will shield the foal from seeing any other patterns for the first day or so. The stripes act as a kind of zoological barcode, allowing one individual to recognise another. Zebra mares do not adopt each others foals. The foal’s voice is also unique, and its survival depends on quick voice and pattern recognition. We saw many young in the various herds of differing ages. The abundance of young was a sure sign that the herd was migrating to new more abundant grasslands.

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The zebra seemed to mingle easily with both topi and eland. The topi were more skittish and prone to gallop off in great numbers at high-speed .   Herbivores in the Serengeti take part in grazing successions in which species follow each other in characteristic sequences during their seasonal movements. In the Serengeti, the succession is zebra first, wildebeest second and lastly Thomson’s gazelle. The semi-migratory topi tend to associate with zebra. 

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Zebra family groups are often thrown into disarray at night due to predator attacks. The next morning, Zebra families spent hours gathering together. The stallions are tireless in the quest to reassemble their family groups, calling until all the family members are together.

“Butterflies and Zebras And moonbeams and fairy tales, That’s all she ever thinks about Riding with the wind.”

~ Jimi Hendrix

On average, Plains Zebras are smaller than the other two species of zebra. They range in height from 1.0-1.5 metres and can weigh almost 450 kg. Plains zebras also have a different stripe pattern to the other species. They have broad stripes that run horizontally towards the back and vertically towards the front, meeting in a triangle in the middle of their bodies. They also have a stripe that runs down the center of their backs onto the tail. Plains Zebras also have underbelly stripes. Although all Plains Zebras share these similarities in stripe patterns, no two zebras have exactly the same pattern.  Foals are usually precocial and are up on their legs around 10 minutes after birth, and are able to walk within half an hour and run after an hour.

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Down at the Ngokeo dam, we found a large herd of zebra where groups were coming down to drink in relays.

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What was unusual about these zebra was that they walked deep into the water. This was unusual because the zebra have to cross a the number of rivers during their migration which are infested with crocodiles.  I would have thought they would have been programmed to be very wary of wading in too deep.

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There must have been something about this dam that indicated to them there were no crocs in it. Perhaps it was that the dam was so far from the nearest river that the chances of  croc making it over land to the water was very remote. 

“The great enemy of the truth is very often not the lie – deliberate, contrived, and dishonest – but the myth – persistent, persuasive, and unrealistic.”
~John F. Kennedy

There were lions everywhere in the Serengeti. On the dam wall there were a couple of bushes and sure enough in the shade of one group of bushes were two young nomad male lions. They were definitely interested in the Zebra but there were too many eyes for them to make a surprise attack.

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Invariably, when the rest of the group were drinking, there was always one zebra with its head up keeping guard.

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The zebra were drinking deeply but their reactions were “hair-triggered”. It took very little to spook them and in a split second they spun around and gallop out of the water in a muddy spray. 

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We must have watched the zebra for over an hour and the two young male lions did not move during that time.

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There were groups of zebras which seemed to have a definite close bond.

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“I asked the Zebra, are you black with white stripes? Or white with black stripes? And the zebra asked me, Are you good with bad habits? Or are you bad with good habits?”

~ Shel Silverstein

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We found many large herds of zebra. They seemed to be clusters of family groups which had combined to walk through the high reed oat grass en mass. There is a strict hierarchy in the line of zebra from highest ranking at the front. The “harem” stallion is usually rear guard.

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The zebra seemed to comfortably mingle with the topi, which were much more reactive to their environment. Perhaps the topi were early warning messengers.

“There is language going on out there- the language of the wild. Roars, snorts, trumpets, squeals, whoops, and chirps all have meaning derived over eons of expression… We have yet to become fluent in the language -and music- of the wild.”

~ Boyd Norton, Serengeti: The Eternal Beginning

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We noticed that zebra, like many antelope drink in an arc, probably to get fresh water.

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These strange striped horse of Africa are fascinating and are good example of the deeper you look into nature the more your discover its complexity and interconnectedness. Evolution has dictated that there is a reason for everything in nature.

“The zebras have arrived, like spirits they float through the ancient treeline. Bodies dancing in the heat haze, feet and legs lost in the mirage.”

~ Dereck Joubert from ‘Patterns in the grass’.

This is the last post from our Serengeti trip in March. A big thank you again to CNP Safaris and Wenzel Kotze for a wonderful, exciting and fascinating 10 days in a place I love.

Explore, seek to understand, marvel at its interconnectedness and let it be.

Have fun,

Mike

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