Precarious rulers of the animal kingdom

This interesting article by Bjorn Carey analyzes why it's the largest animals who often have trouble surviving over the long term. The outstanding example, of course, is the dinosaurs, but there are many contemporary ones as well. A related article by Carey in the same online publication(www.LiveScience.com) reports on the importance of apex predators, normally the largest predators in the food chain, and how they, too, often end up on the endangered list. (For modern top predators, the answer usually is that humans opt to remove them from the ecosystem, often with no idea of the consequences.)