Published online 28 November 2008 | Nature | doi:10.1038/news.2008.1264

News: Q&A

Saving the Majorcan midwife toad

Researchers start gearing up to mitigate the deadly amphibian chytrid fungus in the wild.

Majorcan midwife toadThe Majorcan midwife toad: in need of saving again.NHPA/Chris Mattison

Attempts to bring back the Majorcan midwife toad (Alytes muletensis) from the edge of extinction conservationgoes_bad.html">suffered a blow earlier this year, when researchers discovered that animals bred in captivity and reintroduced to the Spanish island had brought with them the chytrid fungus responsible for devastating the world's amphibian populations1.

Nature News spoke to Trent Garner of the Institute of Zoology, London, one of the researchers who will next year begin the first ever attempt to mitigate the impact of chytrid in the wild.

How did this project get started?

Those involved in the captive breeding and reintroduction programme were getting reports from Majorca of the occasional dead Majorcan midwife in the wild. At that time we were all working very much on the decline of common midwifes across Europe due to chytridiomycosis.

We tested the animals and found they were infected with the fungus. We think we are as close as we can get to proving that the reintroduction programme brought the disease onto the island.

While this research was going on, we were also developing some antifungal treatments for Alytes species in general, originally intended to clean up the captive breeding colonies. Now that we've got that treatment available, we think we can use a pond-by-pond approach to mitigate disease in the wild.

Why are you treating tadpoles and not adults?

The problem with treating adults in this species is you pretty much never see them. When the males have fully matured eggs, they drop them in the pond, so you tend to just see males hopping into the water.

So is it as simple as going out there, catching every tadpole you can and treating them?

At its most basic level, yes.

It takes about three hours' hiking to get to some of these sites, several of which we have to abseil into. And we have to get the permits to do the work, as well as develop the right antifungal treatments.

We plan to work with the people who have the captive breeding programme on the island and hopefully combine cleaning up their captive colony with bringing tadpoles in and treating them as well.

We'll probably be releasing metamorphs and tadpoles back into the site at the end of the year.

How do you ensure that infected adults don't re-infect those you have treated?

Trent GarnerTrent GarnerInstitute of Zoology

We're not sure that the adults are even infected. It seems that in a lot of European amphibians one of the primary agents of disease-related decline is tadpoles infected in the water and mass mortality at metamorphosis, with some method of sustaining the chytrid in the pond between metamorphic events.

If we do have infection in adults, we can't address that directly with this mitigation. But we can definitely assume that the amount of time the adults spend in the water is limited, because they simply drop the clutches and go.

Theory also tells us that if we reduce the number of infected individuals to significantly low levels, it decreases the likelihood of the disease persisting in the environment.

How could you make this a more global approach?

We're going to have to tackle this disease at a regional scale. What we do in Majorca will be different to what we do in the Pyrenees or in the neotropics.

Out of this study we might get proof of principle that you can go out there and reduce the disease's effects on populations, be it to clear the disease right out or prevent the few mortalities we're seeing now.

People tend to think of a wave of chytrid ripping through meso-America and causing 50% of the [amphibian] biodiversity to disappear. They are overwhelmed by this thought. To some degree, those who are working on chytridiomycosis are so busy describing what's happening, they don't have time to mitigate it.

What would the consequences be of not doing this work?

We're not sure yet. If we look at what's happened with chytridiomycosis at a global scale, the outcomes are pretty severe. Some estimates suggest that more than 100 species of amphibians have gone extinct because of it.

However, we've also done research that shows the Majorcan isolate is relatively benign. It does incur mortality in toads in captivity, but much less so than, say, isolates from the United Kingdom or the Pyrenees.

But the fact that it's not virulent now doesn't mean it's going to stay that way forever. Doing nothing is not a good idea. 

  • References

    1. Walker, S. et al. Curr. Biol. doi:10.1016/j.cub.2008.07.033 (2008).
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