Why are cane toads in australia considered an invasive species rather than simply nonnative?

a.) they are destructive to native species and have no natural predators.
b.) they reproduce more quickly than native species.
c.) they have venom glands.
d.) large adult specimens are able to hunt snakes.

A.) They are destructive to native species and have no natural predators.  

An invasive species is a species which when introduced or immigrated to a new ecosystem compete with the native species for resources as a consequence, this species is responsible from elimination, extinction and migration of native species living in an ecosystem. Cane toads in Australia are considered as an invasive species rather than simply nonnative because they are destructive to native species and have no natural predators.  

this is a good question! i'll do some research and come back when i have the answer!