There is an aspect of Creation that many secular biologists scoff at mostly, and it is the Genesis account of all animals being created before sin. So if there was no death before sin, why were carnivores created by God with sharp teeth if they were never created too kill? Lions and tigers and bears all have sharp teeth, why would they have such sharp teeth if original creation was all vegetarians?
Genesis 1:29-30 (New Living Translation)
29 Then God said, “Look! I have given you every seed-bearing plant throughout the earth and all the fruit trees for your food.30 And I have given every green plant as food for all the wild animals, the birds in the sky, and the small animals that scurry along the ground—everything that has life.”
The problem is we all seem to think sharp teeth equals flesh tearing capability. And though this is true, that is not the only function of sharp teeth in the animal kingdom. Sharp teeth can be used to intimidate other animals (like competing males) and well as tear into thick fruits or very fibrous plants. There are many animals with sharp teeth that are strictly herbivores; the fruit bat which eats fruit, the Panda which eats bamboo, or the newest prehistoric animal to be discovered as a herbivore; the Tiarajudens eccentricus which has incredibly large sharp teeth, yet is believe to be strictly a herbivore. See the following link: http://news.nationalgeographic.com/news/2011/03/110324-saber-toothed-sabertooth-vegetarian-science-evolution-tiarajudens/
So as you can see sharp teeth doesn’t necessarily mean carnivore. There are numerous animals in the world today and in the prehistoric past that have sharp teeth, but did not eat meat. Great examples of what the sharp teeth of carnivores were used for prior to the fall.
But we must also consider God’s forsight of the future. “Everything has already been decided. It was known long ago what each person would be. So there’s no use arguing with God about your destiny.” – Ecclesiastes 6:10 (NLT). So though God created everything “good,” he surely knew of the impending fall. So it is very possible God would also prepare animals for a sin cursed world, by providing them with teeth that could be used to kill prey or defend one’s self.
So sharp teeth and other defense mechanisms very well could have had a purpose before the fall, or have been created by God in prepreation for the fall.