Non-Native Species A Brief Account

Many Reptiles are quite difficult to observe due to their nocturnal nature. Hibernation in cold temperatures implies that any spreading range is highly limited by temperature, and Reptiles are mostly confined to sub-tropical and tropical areas. Limited modes of locomotion confine most Reptiles to land and vast expenses of water are not crossed. However, many Snakes, Lizards and Turtles have become popular pets and are transported all over the world. Some secretive Reptiles have remained hidden in vessels from tropical ports and transported to areas where they were not originally found.

Snakes can be pernicious predators of larger vertebrates and arthropods. On islands where the local fauna has developed without the pressure of the presence of these predators, the native avifauna and herpetofauna cannot cope with these exotic, efficient predators and often are disrupted, leading to local extinctions.

Some species of non-native Snakes causing ecosystem impacts where they have been introduced are listed below.

• Common Wolf-Snake (Lycodon aulicus) intimidating the native fauna of Christmas Island.

• Boa constrictor (Boa constrictor) causing potential decimation to large vertebrates on the Mexican island of Cozumel.

There are currently 13000 of these Snakes on the South Pacific Island of Guam per square mile, a stunning concentration that the island's fragile ecosystem cannot handle at all, and Guam has since been quoted as the most notorious example of the potential deleterious effects an introduced species can have on ecosystems, and indeed particularly island ecosystem. However these significantly detrimental impacts were not noticed until 25 years after the introduction of the Tree Snake, by which time it had been too late to save the decimated populations of many island birds and small reptiles living on Guam.

Brown Tree Snake is a mildly poisonous rear-fanged species, with a large head relative to the body size. The Snake is variable in colour from bright green to leafy brown, sometimes with bands around the body. It originates from the tropical rainforests of New Guinea, Solomon Islands and Cape York of North Australia. During World War II it was introduced into Guam via military cargo ships, and the absence of dominant vertebrate predators on the island rendered the native fauna vulnerable to the attack of Brown Tree Snakes.

The Snake is highly adapted to hiding in cramped tree holes and is highly secretive by nature, thus can be widely dispersed by stowing away in plane wheel-walls and under decks aboard ships.

The introduction to Guam during World War II delivered them to an environment where they proliferated without natural predators. In 1950 the first Snakes were discovered in Central Guam, and in the next 20 years most of the native forest birds were already extinct from the island apart from patchy habitats in the North of the island. By 1984, when the endemic forest bird species, whose remaining populations were already severely threatened by the Brown Tree Snake, received the status as Endangered Species requiring special protection, these species were already close to extinction. At present, introduced lizards are still sustaining the population of the Snake so that it remains at a high level, and the Snake is still exerting its pernicious influence on the ecosystem of Guam, beside causing other troubles such as blocking power supply by clinging to power lines. Currently only isolated patches of forest on Guam remains as sanctuaries for the remaining wild birds, and if no effective measures can keep the Brown Tree Snake from invading the rest of the once pristine heaven for island life, the fortunate survivors will soon disappear.

This Slider Turtle is characterized by a red ear patch (nonetheless lacking in some individuals) and grows up to 20cm in length. They are popular pets along with many other Lizards, Chameleons and Snakes, and as a result have become established in many parts of the world, where they compete with native aquatic turtles for food. They are omnivorous and will consume insects, crustaceans, worms, snails, amphibians and small fish; plant matter takes up about 90% of the adult diet, and they gorge on species such as Water Lilies and Hyacinth. Their preferred habitat is quiet pools with a muddy bottom and plenty of aquatic plants, but in captivity they also take dog food, bananas and lettuce. Females lay up to twenty eggs, usually in the warmer months from April to July. Active in all months throughout the year in tropical climates, they hibernate during colder months in logs and burrows.

Natural Sliders occur from the Mississippi valley to California. Introduced establishments have occurred since 1958 in Southern Florida, and it is the second-most common Turtle in Taiwan in many areas, competing with native Turtles for trophic resources and nesting sites. Their mostly plant-oriented diet also means that they can cause excessive damage to aquatic flora in introduced areas. Some Red-eared Sliders have been found to carry the virus Salmonella, which may infect humans and cause health hazards when allowed to escape.

Sarcastically, throughout their native range the Slider is suffering a population decline due to overharvesting for the pet trade, and some Turtles are killed for their meat. The Red-eared Slider is allowed to hybridize with closely related subspecies in the Southern States via human introduction and this undermines the health of the species' genetic stock.



	Species Accounts Snakes* Brown Tree Snake Red-eared Slider