I think Africa invented the thorn. In Serengetti it is hard to find a tree or bush without thorns. Thorns on the trees are easy to avoid but some of the smaller thorns, such as the aptly-named Devil's Thorn have a way of finding their way into your tent, attached to the bottom of shoes or slippers, and then inflicting a little sharp pain when you walk around in socks or barefoot. At both our Serengetti camps shoes are removed before entering the dining tent. We learned to avoid them.
There are from 120 to 200 varieties of acacia trees, all with thorns I suppose. The giraffes eat the small but highly nutritious acacia leaves as their main diet, using a special mouth and tongue technique to avoid the thorns. Unfortunately, I could not get a shot of the giraffe's 45 cm (20-inch) tongue.
The acacia trees have developed an ingenious double-barrel defense against being completely eaten. First, when the tree senses that its leaves are being eaten it sends tannin from the roots up into the leaves making them bitter. Second, it release a gas which, when detected by neighboring acacias causes them to send up tannin. The giraffes are thereby prevented from completely stripping a tree of its leaves. The whistling acacia has another tactic. It plays host to stinging ants in globular nodules around its thorns. They attack giraffes when they attempt to feed. As a result, acacias survive the feedings but giraffes also get enough to survive.
Thorns with red tips from one variety of acacia are used for ear-piercing because when they are heated the tip releases an antiseptic. Using other thorns can cause infection. The Masai use live and dead thorn material like barbed wire, to surround their "bomas" (groups of huts) and corral their livestock to protect them from predators.
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| Thorn-avoidance eating technique. |
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| Masai Boma, reed fence on left, acacia barrier on right. |
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| Snake-eating Secretary Bird nests on acacia. |
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| Lean cuisine. |
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| Closeup |
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| Devil's Thorns |
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| Whistling Acacia. Note stinging ants on bulbous portion |
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| Some turn silvery |
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| Some stay green |
Funny; those devil's thorns look similar to this nasty burr which grows on a grass-like weed around Kitty Hawk, North Carolina, called a sandspur. One "grass" strand has several of these things on it. When they dry out in one's house and fall into carpeting...let's just say that if you step on one, you will emit a stream of oaths.
ReplyDeletehttp://okeechobee.ifas.ufl.edu/News%20columns/Sandspur.htm