In the criminal law in the United States, the definition of a given offense generally includes up to three kinds of elements: the actus reus, or guilty conduct; the mens rea, or guilty mental state; and the attendant (sometimes external) circumstances.
Zebras are herbivores and eat mostly different types of grass, but they also eat bark, herbs and shrubs. Zebras prefer full green grass that is short and near the ground.
Zebra mussel larvae have no special defense against predators, but they are so small that only small predators and filter-feeders eat them. The larvae are part of the zooplankton in the water, and pretty much any predator that eats zooplankton eats them.