The Endangered Species Act (ESA) makes it a crime to “knowingly” take any member of an endangered species. The government has generally interpreted this to require the defendant’s knowledge of each of the elements of the offense; however, it has not been consistent in this interpretation. In several cases, it has argued that the defendant need only have knowingly engaged in an act that resulted in take, and that knowledge that a particular species will be taken is unnecessary. This Article argues that the statute requires knowledge of all the facts, including the identity of the species. In other contexts, the U.S. Supreme Court has required knowledge of the facts constituting an offense, for fear of criminalizing apparently innocent, ordinary conduct. The breadth of the ESA’s take provision and the number and obscurity of the species subject to it counsel in favor of interpreting the statute consistent with this general rule.