Introduced, exotic species from the eastern U.S., such as bullfrogs, bullhead catfish, and bass, are also a threat to the arroyo toad. These species occur widely in reservoirs and altered watercourses such as channelized rivers. In most unaltered southern California streams, these exotic species do poorly, illustrating the advantages that reservoirs and altered habitat provide these invaders. Even with an intact watercourse, arroyo toads suffer from changes to upland habitat the areas beyond the stream banks where they travel to forage and burrow as adults. For species that move out of these areas, the presence of golf courses, houses, or agricultural areas can have very negative impacts on the species.
Roads can be very destructive to arroyo toads and their habitat both in streams and in upland areas.
The toads are run over by cars, sometimes in significant numbers. Plus, vehicles leave lots of nasty deposits which run off the roads and pollute streams. Just a small amount of silt or petroleum by-product pollution can kill arroyo toad eggs and larvae, which are very sensitive. Like many amphibians, arroyo toads are very sensitive to their environments, so habitat destruction and other human impacts make it hard for them to survive. I ve heard that lots of frogs and toads around the world are having trouble deformities, diseases, and disappearances.