Friday, October 31, 2008

Every tree has its thorns

One of the things I noticed on my first visit to Kenya was how many plants are covered with sharp thorns. It seems trees and bushes covered with thorns are more common the those without thorns. After a week or two in the bush the soles of my shoe and sandals were full speckled with thorns. This year I have been wearing my generic crocs around camp, which are very comfortable, but provide the nasty thorns with easy access to the bottom of my foot.

The high density of animals that feed on tree leaves is one reason that so many trees have thorns. The thorns function as a defense against herbivores eating the tree leaves. As with defense in nature, a new offense will inevitably arise. Many adaptations have arisen in the savanna to circumvent the plant defenses. I think the elephants have a particularly interesting method of dealing with the thorns. They just eat them.

In the first picture below you can see the thorns in the foreground and the stripped branches in the background. The arrows are pointing to branches that have had the leaves and thorns removed by an elephant trunk. The second picture is for scale and to help you appreciate the size and strength of the thorns and how tough the elephant trunk, mouth and digestive system are. I was able to push the thorns on the branch into the log quite easily. It should also be evident how thorns of this size could easily go all the way through a human foot, some feet more easily that others.

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