The African crested rat, 14 inches long, would make a hearty meal for predators were it not for its well-advertised deterrent.
Zoologist Jonathan Kingdon of Oxford grew up in Africa and well knew the furry rat’s distasteful reputation. His research has unmasked the rat’s secret to success in a hostile world. Poison!
The crested rat is not equipped with its own poison but instinctively knows where to obtain a potent supply. The rat chews Acokanthera schimperi tree bark, which contains a poisonous cardenolide compound. This drug closely resembles ouabain, an ingredient in arrow poison.1
The crested rat’s adaptation does not end with instinctive knowledge of where to get a poison supply. Kingdon’s team discovered that a strip of unique hairs along the rat’s back are hollow and porous with a wick-like center. The rat chews the bark and then licks the spit onto those hairs. Locked and loaded, the rat is ready to arch its back in fair warning.
Although the poison can kill in sufficient amounts, the rat’s enemies usually learn their lessons without suffering lethal effects. “It isn't really designed to kill. If it killed every time nothing would ever learn that this is distasteful,” Kingdon said.“The way it really works is that you go away and you recover from a terrible experience and you never, ever invite that experience again.” Kingdon recalls seeing a dog quivering in fear when faced with the prospect of a repeat encounter.
The rat is, for unknown reasons, immune to the poison’s effects. “The rats should drop dead every time they chew this stuff,” Kingdon adds.
How did the crested rat acquire these handy adaptations? Kingdon says, “This is an extraordinary thing to have evolved. . . . Evolution has mimicked something that hunters do. . . .[The crested rat] is borrowing from the plant just as the hunters are borrowing from the very same plant.”
Defense-attack structures (DAS) present a challenge for both evolutionists and creationists. From the evolutionary perspective, optimally located hairs structured to wick up poison, instinctive knowledge of how to use the poison, and immunity to the poison must all evolve at the same time in order for natural selection to select only these particularly gifted giant rats for survival. The concept of irreducible complexity is inescapable.
Creationists should only accept biblically consistent explanations. God created a good world without death. Sin brought a curse upon it. Biblical explanations for DAS fall into two main categories. Some DAS are modifications of abilities originally designed for other functions before the curse of sin entered the world. Other DAS, like thorns, were introduced by God to keep things in balance in the fallen world. Natural selection acting on the variations and mutations within the genome has likely acted in both of these areas to allow the best equipped organisms to survive.
Without detailed knowledge of the original created kind to which the crested rat belonged in the pre-Fall world, we can only guess at the history of its DAS. But we can see that an omniscient God equipped this animal with intricate adaptations to survive in a hostile world.
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