Hawaii's unique and isolated ecosystem is famously devoid of several common animal groups, most notably snakes. It is illegal to own or transport any snake to the islands, as they pose a catastrophic threat to native bird populations that evolved without ground predators. Additionally, there are no squirrels, hamsters, gerbils, or porcupines in the wild or as pets. Large land mammals like bears, cougars, or deer are also absent from the native landscape, although some species like axis deer were introduced later and are now considered invasive. Even many common farm animals or exotic pets, like certain types of large parrots and venomous lizards, are strictly prohibited by the Department of Agriculture. This strict isolation helps protect Hawaii's fragile biodiversity, which consists mainly of endemic birds, sea life, and a few bat and seal species.