Science and environment reporter, BBC News
A study has warned that if WNS continues unabated, there is a danger that species will be wiped out in less than two decades Culling will not halt the spread of a disease that has killed a million bats in the US since 2006, a study says.
Researchers reached their conclusion by modelling how white-nose syndrome (WNS) is passed from bat to bat.Writing in Conservation Biology, they add that a cull would not work because the source of the fungal pathogen is believed to occur in the environment.
Earlier studies have warned that WNS could wipe out bat populations in the north-east of the US within 20 years.
Carrying out a cull of bats in areas where the disease is known to be present is one of the options available in an attempt to contain the spread of the killer fungus.
White-nose syndrome
- WNS is associated with a fungus known as Geomyces destructans
- Once present in a colony, WNS can wipe out the entire population
- It was first reported in a cave in New York in February 2006
- The most common visible symptom of an infected bat is a white fungus on the animal's nose, but it can also appear on its wings, ears or tail
- Other symptoms include weight loss and abnormal behaviour, such as flying in daylight or sub-zero temperatures
- Species known to be vulnerable to WNS include: tri-coloured, little brown, big brown, northern long-eared, small-footed and Indiana bats
- There is no known risk to human health
"We developed a model taking into account the complexity of the bat life history, looking at the roosts and the areas where there are large contacts between the bats," said co-author Thomas Hallam from the Department of Ecology and Evolutionary Biology at the University of Tennessee.
"Given the dispersal aspect of the problem and the complexity of hibernating bat ecology, it was a case that these things together certainly meant that culling would not work in the case of bats."WNS, described by some as the worst wildlife health crisis in the US in living memory, is named after a white fungus that appears on the muzzle and/or wings of infected animals.
However, bats with WNS do not always have the characteristic visual symptoms, but may display abnormal behaviour around their hibernacula (caves and mines where bats hibernate during winter months).
These behaviours include flying outside during the day (when their insect prey is not available) in sub-zero temperatures, or clustering near the entrance to the hibernaculum.
Professor Hallam explained that there was a high degree of bat-to-bat interaction, which has been identified as the main way the disease is transmitted, during the course of a year.
In autumn, the mating season brings together large numbers of males and females.
This occurs shortly before colonies enter hibernacula, some of which are large enough to house in the region of half-a-million bats.
In the spring, females head to a maternity roost to have their young. Again, this brings bats into contact with members of different colonies.
Since WNS was first recorded in February 2006 in a commercial cave in New York, it has spread to at least 14 states. Cases have also been recorded in a number of Canadian provinces.
Researchers say the fungus associated with the disease, Geomyces destructans, thrives in the dark, damp conditions - such as caves and mines.
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