MOST INVASIVE CREATURES ON EARTH

AMERICAN COMB JELLY

Commonly called the comb jelly or sea walnut, it is indigenous

to temperate, subtropical estuaries along the Atlantic coast of

North and South America. In the early 1980’s, it was accidentally

introduced via the ballast water of ships to the Black Sea,

where it had a catastrophic effect on the entire ecosystem.

In the last two decades of the twentieth century, it invaded

the Azov, Marmara, and Aegean Seas and was recently

introduced to the Caspian Sea via the ballast water of

oil tankers.

THE NILE PERCH

The Nile perch is a large freshwater fish that can grow up to

200 kg and reach up to two metres in length. It was introduced to

Lake Victoria in 1954, where it has contributed to the extinction

of more than two hundred endemic fish species through

predation and competition for food.

CATS

Believe it or not, the domesticated cat, which can be traced back

three thousand years to the eastern Mediterranean, is one of the

most invasive creatures on Earth. Considering the extent to which

cats are valued as pets, it is not surprising that they have since

been translocated by humans to almost all parts of the world.

Notable predators, cats threaten native birdlife and other fauna,

especially on islands where native species have evolved

in relative isolation from predators.

CANNIBAL SNAIL

The cannibal snail was introduced to Indian and Pacific Ocean

islands from the 1950’s onward as a biological control agent for

the giant African snail. As its name suggests, this snail will eat

anything in its path, even its own kind.

CHINESE FRESHWATER EDIBLE CRAB

Eriocheir sinensis (its scientific name) is a migrating crab that has

invaded Europe and North America from Asia. During mass

migrations it contributes to the temporary disappearance of

native invertebrates. It modifies habitats by causing erosion

due to its intensive burrowing activity and costs fisheries and

aquaculture several hundred thousand dollars a year by

consuming bait and trapped fish as well as by damaging gear.

CARIBBEAN TREE FROG

The Caribbean tree frog is a relatively small tree frog native to

Puerto Rico. Their loud call is the main reason they are considered

a pest, since their two-note “co-qui” can attain nearly one hundred

decibels at 0.5 metres. Caribbean tree frogs are also known for

having a voracious appetite and there are fears in Hawaii that

endemic insect and spider species are at risk due to this

frog’s unusual appetite.

WALKING CATFISH

The walking catfish is native to Southeast Asia and has been

introduced in many places for fish farming. The walking catfish

(named for its ability to move over land) is an opportunistic feeder

and can go for months without food. During a drought large

numbers of walking catfish may congregate in isolated pools and

consume other species, even causing their extinction.

JAPANESE STARFISH

Originally found in far north Pacific waters and areas surrounding

Japan, Russia, North China, and Korea, the northern Pacific sea star

has successfully invaded the southern coasts of Australia and

has the potential to move as far north as Sydney. The sea star will

eat a wide range of prey and has the potential for ecological

and economic harm wherever it finds itself.

RASPBERRY CRAZY ANT

Raspberry crazy ants have invaded native ecosystems and caused

environmental damage from Hawaii to the Seychelles and Zanzibar.

On Christmas Island in the Indian Ocean, they have formed

multi-queen super colonies. They are also decimating the

red land crab (Gecarcoidea natalis) populations. Crazy ants also

prey on, or interfere in, the reproduction of a variety of

arthropods, reptiles, birds, and mammals on the

forest floor and canopy.