Can Using a Waterless Barrier Prevent the Expansion of Invasive Species?

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Cane toads were introduced from Hawaii into Australia in 1935 as part of an effort to curb the cane beetle (Dermolepida albohirtum) and French’s beetle (Lepidiota frenchi) which are eat away at sugar cane crops.  While ultimately the benefit to sugar cane crops by the introduction of this invasive species is questionable, the population and range of toads in Australia has expanded dramatically over the decades.  Researchers estimated that cane toads migrate at an average of 40 kilometers (25 miles) per year [1].

Animated map showing the spread of the Cane Toad (Bufo marinus) throughout Australia from 1939 to 1980 at five year intervals. Map: Froggydarb, Mediawiki Commons.

Animated map showing the spread of the Cane Toad (Bufo marinus) throughout Australia from 1939 to 1980 at five year intervals. Map: Froggydarb, Mediawiki Commons.

Impact of cane toads on native Australian species

The impact of cane toads on native species has been varied. Populations of Northern quoll (Dasyurus hallucatus), a carnivorous marsupial, have declined in the presence of cane toads [2].  Lizards such as the Argus monitor (Varanus panoptes) dropped in population by up to 90% after their habitats were invaded by cane toads.  [3]

Cane toad in Queensland, Australia. Photo: Jon Connell, CC BY 2.0

Cane toad in Queensland, Australia. Photo: Jon Connell, CC BY 2.0

How do water points help cane toads spread?

In western Australia, researchers have proposed a waterless barrier method to halt the spread of cane toads.  Most of this region is arid but livestock and agricultural practices in the area have led to the development of dams, tanks, and bores.  These artificial water points help cane toads to spread by serving as stepping stones for migration during the rainy seasons and refuges for the toads during droughts.  The researchers are proposing creating barriers around these water points that allow cattle access to drinking water why preventing entry by toads.  By eliminating access to open water during dry seasons, researchers hope that this will prevent cane toads from surviving in western Australia.

What are waterless barriers?

Researchers are proposing waterless barriers in the form of simple 60cm fences which can be placed around dams and other open water sources.  These fences prevent toads from access water needed for survival.  The fences would need to be placed strategically in the region to create a barrier that is 50 km across.  Researchers believe this would be effective enough to stop the migration of can toads into Western Australia.

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References

[1] Tyler, M. J. (1994). Australian Frogs A Natural History. Reed Books. p. 112. ISBN 0-7301-0468-0.

[2] Mayes, P. J., Thompson, G. G., & Withers, P. C. (2005). Diet and foraging behaviour of the semi-aquatic Varanus mertensi (Reptilia: Varanidae). Wildlife Research, 32(1), 67-74.

[3] Doody, J. S., Green, B., Sims, R., & Rhind, D. (2007). A preliminary assessment of the impacts of invasive cane toads (Bufo marinus) on three species of varanid lizards in Australia. Mertensiella, 16, 218-227.

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