You are what you eat

I was at the National Zoo in DC yesterday. I haven't been to a zoo in probably 15 years, but it's nice to know that 2.5 science degrees later, I can still learn a thing or two from such an outing. In this instance, I discovered that the beautiful but deadly 'poison dart frogs' are not naturally toxic. Raised in captivity, these amphibians are harmless. The reason for their toxicity is the accumulation of alkaloid compounds from ants and other arthropods that they consume. This is true of frogs from Madagascar as well as those from Australia or South America. Geographically isolated, the ants that are the source of the toxin for frogs from these regions are not closely related, making this a cool example of convergent co-evolution of arthropod and frog species.