Invasive species are species that are not native to an area, or are outside of their natural distribution area. Since they don’t have natural enemies and constraints like they do in their native habitats, they are able to spread rapidly, dominate natural areas, and outcompete and predate on native species. Invasive species are recognized globally as the second greatest threat to biodiversity (after direct habitat loss due to humans) and have proven to be problematic for indigenous reptile and amphibian species. Invasive species can negatively impact B.C.’s environment, people, and economy.
There are four invasive species of reptiles and amphibians that are currently established in British Columbia:
European Wall Lizard
European Wall Lizards were introduced to B.C. in the 1970’s when a private zoo near Victoria closed and released them into the wild. Since this time Wall Lizards have expanded their range rapidly across Vancouver Island and there have been reported sightings in Vancouver and Osoyoos. Wall Lizards may spread by being transported on vehicles or through human release of pets. They pose a threat to our native lizard species, the Northern Alligator Lizard. Wall Lizards can reproduce more rapidly and reach maturity earlier than Alligator Lizards, meaning they can quickly outnumber our native species. This may mean that Alligator Lizards will have to compete with this introduced species for food and suitable habitat. Additionally, Wall Lizards have been found to thrive in warmer temperatures, meaning they may fare well with increasing temperatures due to climate change.
American Bullfrogs naturally occur in eastern North America but are considered invasive in British Columbia. They were introduced to B.C. in the 1900’s for frog leg farming purposes. Since this time, Bullfrogs have rapidly spread throughout the Lower Mainland and southern Vancouver Island as well as into western United States. Bullfrogs in B.C. have a huge impact on local ecosystems. They are the largest frogs in Canada (as big as 20 cm in body length), and will eat anything that can fit in their large mouths including other frog species, salamanders, turtles, snakes, lizards and even fish, birds, and small mammals. Bullfrog tadpoles also compete with native frog tadpoles for resources and suitable habitat. In particular Pacific Treefrogs and Red-legged Frogs are negatively impacted by the presence of Bullfrogs. Bullfrogs are also a carrier of Chytrid disease, which is a highly contagious fungus that is detrimental to amphibians.
(Trachemys scripta elegans)
Red-eared Sliders are native to the southeastern United States, Mexico, Central America, and Brazil. These turtles have been introduced to B.C. by pet-owners abandoning them in our lakes and ponds. Unfortunately, when pet-owners purchase Red-eared Sliders they do not realize how long they can live (sometimes up to 20-30 years!), and often abandon them when they decide they cannot offer life-long care. Red-eared Sliders introduce diseases to our native turtle species, as well as compete with them for for food, nesting sites and basking habitat – all of which are already limited due to habitat loss. They can be distinguished from the native Western Painted Turtle by their yellow belly and a red streak behind their eye.