It is not a great time to be an amphibian. Of the described species, 1856 are globally threatened (listed on the IUCN Red List) – a number which amounts to 32% of all amphibian species! As well as dealing with the usual threats of habitat destruction, climate change and exploitation; amphibians have been faced with a global crisis – a pandemic pathogen.
The fungus Bd (Batrachochytrium dendrobatidis) is the causative agent of the amphibian disease Chytridiomycosis – let’s call it Chytrid for short. Chytrid was first identified in populations of amphibians in Australia and Central America. From here the fungal disease has spread into six continents and been responsible for mass mortalities of worldwide amphibian populations – and one extinction … so far.
The Chytrid disease is a real ‘millennium’ bug - it was first discovered in Europe during 2000, when it was found in captive populations of toads in Germany. In 2001, the first wild infection was recorded in Spain, leading to a huge decline in a population of common midwife toads. It is now present in seven European countries and has been documented to affect over 20 different species. It is definitely not a good time to be an amphibian…
How it this all related to invasive species?
Three invasive non-native amphibians have been identified as the global vectors of this epidemic: the cane toad (Bufo marinus), African clawed frog (Xenopus laevis) and the American bullfrog (Rana catesbeiana). All these species can carry the Chytrid fungus, but are immune to the disease itself. This means they can spread the disease amongst native amphibian populations while not enduring any of the negative effects themselves.
These three species have already been transported widely outside of their native range, being introduced for food, as biological control agents and through the pet trade.
In Great Britain, the American bullfrog is an Alert species. The species is twice as long as our common frog and has a deep distinctive call. Download our free Smartphone app for more information on this species and keep your eyes peeled for this froggy fiend...
Duffus, A. L. J., Cunningham, A. A (2010). ‘Major disease threats to European Amphibians’ Herpetological Journal 20: 117-127
Kaefer, I.L., Boelter, R. A., Cechin, S. Z (2007). ‘Reproductive biology of the invasive bullfrog Lithobates catesbeianus, in southernBrazil’ Ann. Zool. Fennici. 44: 435-444
Stuart, S. N., Chanson, J. S., Cox, N, A., Young, B. E., Rodrigues, A. S. L., Fischman, D. L and Waller, R. W (2004). ‘Status and trends of amphibian declines and extinctions worldwide’ Science 306: 1783 - 1786
Photo Credits: Frog (Liquid Ghoul); Cane Toad (Brian Gratwicke), African Clawed Frog (Brian Gratwicke) and American Bullfrog (Carl D Howe).