There are a lot of "feral" animals on the Hawaiian Islands, as everywhere else.
The first settlers brought many with them, others arrived as stowaways on
ships or were brought over in the expectation of being able to control one or
more of these species which have become "pests". The goats are only one
of many examples. Roosters and hens, now feral, wild boars, mongoose, rats
and quite a few others are more examples of misguided introduction attempts.
Wlld goats now strip the ground of its cover, aiding the rapid erosion of many
hillsides, valleys and other natural areas.. Having done that, they then turn to
stripping bushes and trees of their lower leaves and branches. Wild boars
uproot farmers' planted fields, mongoose eat native bird eggs, while the rats
they were supposed to control and eat flourish. Man stands by helpless.