Click on some of the thumbnails below and decide for yourself if you'd risk climbing this tree. My guess is that the leaves of this tree are particularly desirable to some or other creature and that these super-pointy thorns server as deterrents.

Speaking of deterrents... while in the Kruger National Park our guide pointed out a bush that defends itself from buck by releasing a bad-tasting chemical into its leaves if senses that too many have been eaten. The chemical is also released into the air (which in turn starts a chain reaction in neighbouring bushes, which in turn release the chemical into their leaves. Sneaky isn't it?