Toads
have disappeared from 2/3rds of known habitats
December 2012. The emergence of chytridiomycosis is now widely recognized as a
major cause of amphibian declines and biodiversity loss on local and global
scales. Amphibian mortalities caused by the pathogenic chytrid fungus
(Batrachochytrium dendrobatidis (Bd)) were first recorded in Iberia, Europe
over a decade ago.
In
August 2009, hundreds of post-metamorphic common Midwife toads (Alytes
obstetricans) were found dead in the water and margins of a pond in the Serra
da Estrela Natural Park, north-central Portugal, and analyses confirmed their
infection with Bd. Given the likelihood of a new outbreak of chytridiomycosis,
staff from Durrell Institute of Conservation and Ecology, School of
Anthropology and Conservation, evaluated the possible impacts of this disease
on populations of Midwife toads within the Park by conducting field surveys
during 2010 and 2011.
They
compared the present distribution and abundance of Midwife toads with
historical records, and quantified the present prevalence and intensity of
infection by Bd. Results showed that Midwife toads had disappeared from 67% of
the 1 x 1 km squares where it had been recorded previously. Results also showed
that breeding is currently limited to just 16% of the confirmed known breeding
sites and that larvae are now less abundant. There is also a high incidence of
Bd in the remaining sites.
These
effects were most pronounced at altitudes above 1200 m. The findings suggest
that an outbreak of chytridiomycosis is responsible for the rapid decline of
Midwife toads in Serra da Estrela, and it is believed that urgent conservation
measures are needed to prevent local extinction of the species.
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