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Understanding animals through their behaviour

FROG AND TOAD DEATHS AND DISEASES

Dead frog found in pond early spring. Possibly drowned due to premature amplexus. c. Celia Haddon

In early spring, dead frogs are often found floating in ponds because they were trapped under ice. If there is freezing weather for three continuous nights and the ice is more than an inch thick, oxygen can’t get in and various toxic gases like carbon monoxide and sulphur dioxide can’t get out. Frogs and fishes suffocate. To stop this happening, fill a plastic bottle quarter full of gravel and float it on the pond. This  will allow  gases to escape when the pond is iced over.

But there is also a new infectious virus, Ranavirus, which is killing our frogs. The frogs turn red on their legs, chests, or bellies. Froglife are studying this disease, and would like to hear from you, with photos and descriptions. But please don’t send them corpses however well packaged! It seems that toads are also suffering from this disease or something similar too (Cunningham et al., 2006). Ranavirus sometimes kills off every single frog in a pond, sometimes some survive but there are recurring outbreaks, and some populations recover completely (Teacher et al., 2010). Perhaps some populations are resistant to the disease or maybe there are different strands of disease varying in virulence.

Another threat to UK amphibians is ‘chytrid fungus’, a fungal infection that may have been endemic in Africa before spreading elsewhere (Weldon et al., 2004) that is thought to be related to the enormous decline of amphibians worldwide – 1/3 of all amphibians are faced with extinction. It was discovered in a non-native bullfrog colony in the UK in October 2005 – the most significant symptom is large-scale mortality of juveniles on emergence from the pond. It is thought this disease is of most threat to common toads -   Froglife urgently want people to get in touch if they think they have seen signs of this in their pond or ponds at nearby nature reserves. There is the possibility that a bacteria found on the skin of some frogs may protect against this disease (Harris et al., 2009)

REFERENCES

Cunningham, A.A., Hyatt, A. D., Russell, P. & Bennett, P.M.,  (2006) ‘Experimental transmission of a ranavirus disease of common toads (Bufo bufo) to common frogs (Rana temporaria)Epidemiol. Infect. (2007), 135, 1213–1216.

Froglife, (2013), ‘Amphibian Health and Disease,’  Peterborough, UK, Froglife. Available at www.froglife.org Accessed April 12 2013.

Harris, R. N., Brucker R. M., Jenifer B Walke, J. B.,  Matthew H Becker M. H.,  Schwantes, C. R., Flaherty D. C., Lam, B. A., Woodhams, D. C., Briggs, C. J., Vredenburg, V. T. &  Minbiole, K. C. B., (2009), ‘Skin microbes on frogs prevent morbidity and mortality caused by a lethal skin,’ International Society for Microbial Ecology Journal, 1-7
fungus

Teacher, A. G. F., Cunningham, A.A. & Garner,T. W. J.,  (2010), ‘Assessing the long-term impact of Ranavirus infection in wild common frog populations,’ Animal Conservation, 13, 514–522.

Weldon, C., du Preez, L. H., Hyatt, A. D., Muller, R. & Speare, R. , (2004),’Origin of the Amphibian Chytrid Fungus’, Emerging Infectious Diseases, 10, 2100-2105

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