Double whammy for the disappearing frogs

New species of red-eyed toad New frog and toad species are being discovered - others may be wiped out before being identified

There's a strange twist this week to the long-running story of the disappearing frogs.

As regular readers of these pages will know, frogs and their amphibian cousins, the salamanders and caecilians, are more threatened than any other group of animals, with more than a third of assessed species on the danger list.

With some species, it's easy to find a single culprit for the decline. With others, as I've noted before, it's a bit of this and a bit of that - the attack of the killer everything.

Usually, the various threats are symbiotic; pollution reduces resistance to disease, for example, while loss of habitat caused by expansion of the human footprint also brings invasive species.

Frog's eye (Image: AP) The study reveals something rarely seen before

This week's unusual twist comes in the shape of a paper in Proceedings of the National Academy of Sciences (PNAS), which suggests a very different relationship between two of the major amphibian threats: loss of habitat, and the fungal disease chytridiomycosis.

Gui Becker and Kelly Zamudio from Cornell University in the US analysed statistics on amphibian decline in Brazil, Costa Rica and Australia, and found that chytrid appears to do more damage in pristine forests than in lands that have been cleared or otherwise modified by human hands.

Why this should be the case isn't entirely clear.

One possible link is temperature; where forests have been cleared, daytime temperatures will be higher (at least in the regions studied), and the Batrachochytrium dendrobatidis (Bd) fungus doesn't like such hot conditions.

An alternative idea is that the greater diversity of amphibian species in virgin forest helps the fungus to spread.

Each species will breed, for example, or disperse, at a different point in the year; so the more species there are, the more frequent these events will be.

And these activities are likely to carry the fungus from one place to another.

The finding has been greeted with some caution, and Nature News carries a good discussion of arguments over what might lie behind it.

The Cornell team now plans to do some laboratory experiments to see whether species richness does encourage chytrid to spread.

Scarlet frog The scarlet frog of Venezuela may have been a victim of chytridiomycosis

In the meantime, if the finding is correct, what does it mean?

One interpretation is that there is now "no hiding place", in Gui Becker's words - with amphibians damned either by loss of their home, or by the visit of a lethal fungus that prefers to knock at unopened doors.

Comments by Karen Lips, one of the world authorities on chytrid, on the Nature post amplify the point.

"This is now a Bd world," she says.

With the fungus active on every continent except Antarctica, the point is well made.

What the new work doesn't do is point a way forward for conservation. Encouraging the destruction of habitat in order to hinder the spread of a disease would hardly be a rational strategy.

But it does confirm that just preserving tracts of intact forest and wetland isn't going to be enough to save all the extant species of amphibian.

Doing that is likely to need something that can tackle chytrid in the wild - which, as yet, does not exist.

Richard Black Article written by Richard Black Richard Black Former environment correspondent

Farewell and thanks for reading

This is my last entry for this page - I'm leaving the BBC to work, initially, on ocean conservation issues.

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  • rate this

    Comment number 47.

    Hi - I am new here, and I am here because a frog moved into the 'water feature' in my back yard - an old iron bath tub with water plants and solar fountain. I live in upstate NY. Can anyone help me with information about how to keep him safe this winter? The tub will freeze over. I can keep a hole in the ice for air, but I am worried that won't be enough. I think he is a green frog. Any ideas?

  • rate this

    Comment number 46.

    @ 10. blefuscu

    Water-borne and direct frog to frog contact are not the same thing - you can't catch cholera by hugging someone! I don't think keeping biologists 'out' will help increase our knowledge and therefore ability to take positive action.

  • rate this

    Comment number 45.

    "Nature tends toward balance."

    No it doesn't, this was disproved in the 1970s with the in depth study of grasslands in the US - the more detailed you look at nature, the more you notice that things are changing and never go back to the way the were. There is no balance or equilibirum, just perpetual change and adjustment.

  • rate this

    Comment number 44.

    Frogs make mistakes too

  • rate this

    Comment number 43.

    Plants and animals adjust over time or disappear. Would not jump to any conclusions based on a point in time study. Nature tends toward balance. Sometimes that is difficult, especially when human beings can create environments in days or weeks that would have taken hundreds of years in some natural process. Humans make many mistakes..i.e. History.

  • rate this

    Comment number 42.

    Since Nature is never in a state of balance, always in flux, & this planet has, over billions of years, been host to billions of uncounted lost species of flora & fauna... then surely the disappearance of even an entire genus shouldn't matter a jot.

    Earth will, as it has done billions of times before, readjust & the mess that is natural Nature will go on... even without frogs!

    Worry not!

  • rate this

    Comment number 41.


    you're correct, the paper implies but doen't cite any specific evidence

  • rate this

    Comment number 40.

    #34 - Thanks SG. And it is not just herptologists taking these precautions. Many - I would hope all - researchers looking at different similar habitats (e.g., for dragonflies etc.) are doing the same.

    #35 Great! That ought to help. Me not up to date.

    #36 Looks at one way this fungus jumped continents to start it all.

    #38 Sorry to hear that. Made false assumption based on your comment.

  • rate this

    Comment number 39.

    MangoChutneyUKOK #37: "my response was to..."

    There is a subtle difference which you seem to have missed.

    My link is to a report concerning "mounting evidence" of spread of disease via "trade".

    The report you linked to does not present any evidence of contamination by researchers. It simply presents ways of minimising it.


  • rate this

    Comment number 38.

    #29 cr
    "You clearly have no clue about the full impact of Mao's Cultural Revolution."

    your mystical way of devining what others do or don't know is broken. i have very personal experience, my father in law still suffers the health effects of his exile under mao's abominable social expt.

    because i'm not a member of the cult of the invisible hand does not make me an apologist for communism

  • rate this

    Comment number 37.

    interesting link davblo

    my response was to HW who claimed there was "absence of studies even addressing the issue of biologist based spread", which is patently false

  • rate this

    Comment number 36.

    MangoChutneyUKOK #35: "Get your facts right..."

    Equally, or maybe more so...

    "The global trade in amphibians entails the transport of tens of millions of live animals each year."

    "...there is mounting evidence that ... the aetiological agents of chytridiomycosis and ranaviral disease, respectively, are spread through this trade.


  • rate this

    Comment number 35.

    @HW #31

    Get your facts right HW:

    "Minimising exposure of amphibians to pathogens during field studies"

    (Peer-reviewed and published - perhaps Richard should have mentioned this paper?

  • rate this

    Comment number 34.

    Hello CanadianRockies
    Your comment interested me the most out of all the comments, and I believe your observation is highly relevant for a number of reasons. Seemingly unrelated events, probably, can be traced back to lack of caution somewhere along the line.

  • rate this

    Comment number 33.

    #31 - The herptologists I know accept the fact that they spread this fungus and that became obvious when it consistently showed up in sites AFTER they first checked them. They now act accordingly, with expected results. Don't expect to see any published papers. They would rather it just quietly goes away.
    #32 - Funny. But not close. You remind me of some recent additions to my old profession.

  • rate this

    Comment number 32.

    CR reminds me of a long ago colleague, an admitted libertarian anarchist, who advocated everyone having their own personal nuclear weapon to end the property tax. The idea was if the state tried to collect tax, the home owner would blow him or herself up along with the rest of the county. This was of course decades before Bin Laden and al Qaeda. He made a profit on a conference on the topic.

  • rate this

    Comment number 31.

    It is interesting how the same folks who say there isn't enough evidence or quality analysis to accept AGW are so ready to blame the spread of the fungus on biologists in the absence of studies even addressing the issue of biologist based spread.

    This trait is perhaps best understood by looking at their political agenda.. .

  • rate this

    Comment number 30.

    WendyRainbow @ 11 said “people will just have to eat something else.”


  • rate this

    Comment number 29.

    #.26. "#23 "Wolfie you really do sound like Mao extolling the Cultural Revolution of Pol Pot."

    The "of" was a typo. Should have been "or." But after I noticed that I left it. Close enough. You clearly have no clue about the full impact of Mao's Cultural Revolution. Wolfie is a closet totalitarian using 'green' excuses = Watermelon.

  • rate this

    Comment number 28.

    #27 - Protocols in place here now, after the fact. Scenario here plus links in #12, 13 suggest there may be hope for some if not many species in any case. Evolution marches on, and amphibians have been around for a very long time.

    Either way, globalization + researchers or ecotourists or pet/other trade
    is a huge problem. What will be spread next?


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