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7 Problematic Invasive Species in Hawaii (Pictures)

Hawaii is plagued by many different invasive species. All of these species present a serious threat to the native wildlife, but dealing with these threats is easier said than done. In this respect, Hawaii is not unique to other states since invasive species are everywhere. Even worse, these beautiful islands are especially vulnerable to them. In this article we’ll have a look at some of the more well known invasive species in Hawaii.

But first, let’s define invasive species.

Collage photo invasive species in Hawaii

W​hat are invasive species?

A​n invasive species is a non-native species that thrives in a new environment where it has no predators, and causes harm to the local ecosystem. There are invasive species everywhere, and they are usually, but not always, introduced by humans. They can be introduced accidentally, but they are often introduced intentionally either in an attempt to provide livestock or game, or to control another invasive species.

Invasive species cause problems because they have no natural predators, which means there are no natural controls on their population size. In addition, the plants and animals they eat have no natural defenses against them, which means they have an unusually large impact on the native species.

7 Invasive Species in Hawaii

Much like Florida, Hawaii is plagued by dozens of invasive species. The following list of invasive species in Hawaii are among the most common and the most problematic.

1. Feral cats

image: pixabay.com

Feral cats have become an invasive species almost everywhere that humans have spread. However, in many places, there are native species of small cat, and so the local wildlife has already adapted to cat predation and has strong defensive measures to protect themselves from cats.

I​n Hawaii, that’s not the case. There are no native mammalian predators on land, and so the local terrestrial species have no natural defenses. Feral cats are devastating predators with voracious appetites, but they also kill for fun. They’re one of the only species of animal that will kill even when they have no intention of eating what they kill.

2. A​sian mongoose

Asian mongoose

Mongooses were originally introduced to Hawaii in the 1880s in an attempt to control the rat population in the sugarcane plantations. This was a misguided action because, while mongooses do eat rodents, they also hunt birds, insects, and reptiles. In Hawaii, the native wildlife has no defense against the mongoose, and most of the birds nest on the ground, where their eggs are easy targets for mongooses.

I​n fact, the mongoose has had almost no impact on the rat population at all, while it’s devastated the populations of native birds.

3. Feral pigs

Feral pigs | image by ALAN SCHMIERER via Flickr

These wild pigs were first introduced by the Polynesian people who first settled the Hawaiian islands. They were a vital source of food for these people. The pigs cause damage to the native habitats by damaging the plant life and eating the eggs of nesting birds.

Feral pigs are a nuisance everywhere they spread, and they have no natural predators except for humans. Because they’re large aggressive creatures with sharp tusks, they can even be somewhat dangerous to humans.

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Feral pigs damage both native plant life and animal life, and have been introduced to Hawaii twice- once 1500 years ago by the Polynesian colonists, and once again in the late 1700s by European visitors.

4. Brown tree snake

image by U.S. Department of Agriculture via Flickr | CC BY 2.0

These rear-fanged, tree-dwelling snakes are native to Australia, Indonesia, and Papua New Guinea. They hunt birds, lizards, bats and sometimes rodents. They’re a notorious invasive species throughout the Pacific, and that includes Hawaii.

Because they eat birds, and have no native predators in Hawaii, they could potentially wipe out many of the native species. This has already happened on the island of Guam, where most of the native vertebrates have gone extinct as a result of the accidental introduction of the brown tree snake.

Hawaii’s infestation doesn’t appear to be significant yet. Direct military flights from Guam to Hawaii are common and brown tree snakes are commonly intercepted at the landing sites.

5. A​xis Deer

First given as a gift to King Kamehameha V, the axis deer were released into the wild and quickly spread. There are now tens of thousands of these deer roaming the islands where they have no native predators. They are extremely destructive to native plant life and they disrupt the nesting areas of native birds, which harms their populations.

A​xis deer are now commonly hunted in Hawaii, where they are prized for their meat and for the money they bring in from prize hunters. There is some controversy over this, though, as many people would prefer they be exterminated altogether.

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6. R​ats

T​here are multiple species of rat in Hawaii, none of which are native. Some were introduced when the first Polynesians colonized the islands, and others when the first Europeans visited the islands. All of them are highly destructive to native wildlife.

Rats eat the eggs and chicks of birds that nest on the ground, and nearly all of Hawaii’s native birds nest on the ground. That’s because they evolved with no land predators, so there was no reason for them to build their nests in trees.

As a result, rats have devastated the native bird populations. Feral cats do eat rats, as do mongoose and Hawaiian hawks and owls, but rats breed so quickly that these predators simply can’t control the population.

7. Jackson’s Chameleon

image: Pixabay.com

Jackson’s chameleons were almost certainly introduced as part of the illegal pet trade. Some of them escaped and established a breeding population in the wild. Hawaii, Maui, and Oahu all have established populations of Jackson’s chameleons.

These chameleons feed on native insects, but they have no predators in Hawaii, which means they pose a serious threat to many of Hawaii’s native invertebrates. In addition, they also represent a good prey species for the brown tree snake. That means they could potentially make it easier for a large population of brown tree snakes to establish itself in Hawaii.