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Snakes in decline


Open channels drain of swamps in the SE of South Australia Clearing of native vegetation on Eyre Peninsula Bridal Creeper on Kangaroo Island

Like many native animals, our venomous snakes have suffered the same fate. Many species are in decline. Here in South Australia, the pygmy copperhead from the Adelaide Hills/Kangaroo Island and the Kreffts tiger snake from the lower Flinders Ranges are in the most insecure positions. Both species are probably best described as vulnerable but further habitat losses will seriously impact on their numbers. All other species, with the exception of the common brown snake, although still common, are also in general decline, coinciding with habitat loss and both direct losses to and competition with feral animals such as cats and foxes.

About 30 years ago, tiger snakes used to be the most common cause of snakebite and death in Australia. Today, brown snakes have surpassed them and now comprise about 75% of bites and deaths to humans and animals. The demise of tiger snakes has been the loss of habitat and habitat decline along watercourses and wetlands. Compounding their problem has been the worldwide reduction in frog numbers that are their favorite food. Causes for this are still unclear but there is emerging concern over the use of some herbicides which have been shown to cause genetic abnormalities in frogs. Wildlife laws pretending to protect them from direct harvesting have been an abject failure at making any impact on their conservation status because collecting or killing them for any reason has been and still is a negligible impact.

Bridal creeper, an introduced plant that is highly invasive, in some areas of tiger snake, copperhead and death adder habitat bridal creeper has smothered native vegetation causing vast habitat changes and ultimate loss in species diversity.

Another species suffering decline has been the common death adder. This secretive cryptic species relies heavily on natural bushland and coastal heath for its survival. Grazing and land clearing have affected this species severely. It uses natural leaf litter to hide in for both its protection and also as a hiding place whilst it waits in ambush for prey animals to venture close enough for a strike.

Feral animals also have a dramatic effect on native wildlife including snakes. Cats and foxes are estimated to cull about 6.4 billion native animals from Australia each year. A significant proportion of prey items taken by cats and foxes are also prey items for snakes. Not only are cats and foxes a direct threat resulting from predation but also provide competition.