Hawaii’s Invasive Species

The Hawaii Islands archipelago is one of the most isolated places on planet Earth.  Located almost at the center of the Pacific Ocean, it is the home of many animal and plant species that are found nowhere else in the world.  And, similar to other isolated island environments, the Hawaiian Islands are especially vulnerable to invasions of non-native species because the invaders usually face no natural predators, and they fiercely compete with native species for food and habitat. 

In order to prevent the further demise of native species of plant and animals, the State of Hawaii devotes what resources it can to intercept arrivals of non-native species at Hawaii’s ports of entry. In September, the State of Hawaii Department of Agriculture, Plant Quarantine Branch held an open house to educate the public about some of Hawaii’s current invasive species threats. 

In the entrance lobby, there were glass showcases with displays of preserved non-native plants, reptiles, insects and even small mammals – judging from the condition of the preserved specimens, I would say that they had been confiscated many years in the past.

Walking deeper into the facility, part of the office had been converted into a temporary display room.  Poster displays explained the most current invasive threats such as the Coconut Rhinoceros Beetle which feeds on plants such as coconut trees and palm trees.  It is feared that the beetle could cause the loss of large numbers of Hawaii’s palm trees, many of which are planted in the state’s popular resort areas.  A landscape of dying palm trees would damage Hawaii’s image as a tropical paradise and cause great economic loss to Hawaii’s tourism industry.

There were also a number of living animals on display, some of which had been confiscated from people who had brought them into Hawaii as pets.

Bearded Dragon (Pogona spp.)

This lizard is native to Australia and males can grow to a length of 2 feet long.  (Females grow to about 20 inches.)  This animal is legal to possess in some states in the US, but illegal in Hawaii.  If allowed into the wild, it would have no natural predator and could threaten native species of insects, invertebrates and birds.

Ball Python (Python regius)

In recent years, confiscated specimens like this Ball Python have occasionally popped up as surrendered pets.  The only snakes which are supposed to be found in Hawaii are sea snakes and the tiny Island Blind snake (Ramphotyphlops braminus).  The small blind snake is usually less than 8 inches, and was first spotted in 1930 on the grounds of what is now known as the Bishop Museum.  It is thought that the snakes arrived in Hawaii as stowaways in the soil surrounding potted trees which were imported from the Philippines for landscaping.  While the tiny blind snake has already spread to all of the main Hawaiian Islands and is deemed harmless, the state is very serious about keeping additional snakes out of Hawaii.  When one considers the environmental havoc that the introduction of the Brown Tree Snake (Boiga Irregularis) has caused in Guam, Hawaii’s high level of vigilance is easy to understand. If a Ball Python were to escape and reproduce in Hawaii's forests, the results would be catastrophic.

Piranha (Pygocentrus spp.)

Native to South America, the Piranha is famous for its sharp teeth and aggressive feeding habits.  For some fish enthusiasts, that aggressive nature makes the fish even more attractive, and many will ignore the law to raise them illegally.  Many years ago, we were told to not worry too much about piranha in Hawaii's waters because the South American piranha supposedly could not survive the colder freshwater temperatures of Hawaii’s lakes, streams and ponds in the winter.  But, with the advance of global warming, I wonder if piranha thriving in Hawaii’s bodies of fresh water might be just a matter of time.

Tarantula (Theraphosidae spp.)

These creatures are usually brought into Hawaii as pets.  They have no local predators, and if they established in Hawaii, they could cause great impacts on Hawaii’s endemic insect populations.

Red-Tailed Catfish (Phractocephalus hemioliopterus)

This native of South America is very popular as a pet, but because it can grow to over 3 feet long in the wild, it would cause great damage to native fresh water animals if it were to establish itself in Hawaii’s streams.  It is now illegal for the public in Hawaii to possess this fish.

Madagascar Giant Day Gecko (Phelsuma grandis)

Native to Madagascar, this gecko is a popular pet.  Unauthorized releases have allowed this animal to establish itself in some parts of Oahu Island.  Growing up to 12 inches, it is feared that further spread of this animal will cause damage to native invertebrates and insects, and possibly even to small birds and eggs. 

Coqui Frog (Eleutherodactylus coqui)

This Puerto Rico native is suspected of entering Hawaii as an accidental stowaway on shipments of tropical plants.  Even today, the worst infestations of Coquis reportedly occur in agricultural areas near where tropical plants and flowers are produced.  Although very small (maximum size about 2 inches) the males have a very loud mating call which sounds like a bird-like chirp.  (The calls of a group of Coquis were once measured to be 80 to 90 decibels at a distance of one foot.)  Local residents say that these loud mating calls are a nuisance that makes it difficult to sleep.  The Coqui hides itself in leaves during the day making them difficult to find and are apparently much easier to discover at night when they are chirping.  With no natural predators to control their numbers, increasing numbers of Coquis cause decreases in the numbers of insects (including plant pollinators) which results in less food for Hawaii’s native birds.  Intentionally transporting, harboring, or importing Coquis with the intent to propagate, sell, or release them is a serious violation of Hawaii State law.