[Fosc] frogs

Walter Epp for7gen at idiom.com
Tue Sep 2 14:54:13 PDT 2008


Good places to start for a general introduction, including lists of
suspected culprits, are:

Amphibian declines: an issue overview, JK Reaser 2000,
Federal Taskforce on Amphibian Declines and Deformities,
http://www.frogweb.gov/declines.pdf

http://en.wikipedia.org/wiki/Decline_in_amphibian_populations

http://amphibiaweb.org/declines/declines.html

For what we can do:

Amphibian Conservation Alliance http://www.frogs.org has action alerts;
they started in Berkeley and Oakland so there may still be local connections
despite moving its office to the Washington DC area

Partners in Amphibian and Reptile Conservation has habitat management guides at
http://www.parcplace.org/habitat_management_guide.html

See my separate message on the attack on the Endangered Species Act, which is
important for amphibians because they are disproportionately endangered.

Let your neighbors know what's happening to the frogs and what they need to
stay here.

If you have specifics on your observations of frog calls, they can be entered
at Frogwatch USA http://www.nwf.org/frogwatchUSA/
Especially if done in some kind of consistent and persistent manner, such
observations can provide feedback on how well or poorly we're doing on making
Sausal hospitable for frogs.

Frogs are quite sensitive to toxics. Is anyone using pesticides or other toxics
in the area?  For more info see references at bottom.

Pesticides may be one of the significant reasons frogs are disappearing
even in pristine places like Yosemite [Newsweek 13 May 2002 p46].
Atrazine, one of the most commonly used herbicides, is harmful to frogs at
100 parts per trillion, 120 times lower than EPA exposure limit.
This was not discovered until 38 years after it was allowed on the market.
It can be carried long distances on wind and rain.

Since frogs are insect eaters, insecticides are liable to be especially
problematic.  The more insecticides are used, the more frogs and other insect
predators are messed up, so ultimately you're liable to get more insects.
That's how pesticide companies make their living - if they can suck you into
the vicious circle they laugh all the way to the bank.

While fungicides and herbicides are different, a similar phenomenon can occur,
by interfering with beneficial parts of the soil ecology that plants depend on,
thus shifting conditions in favor of weedier species.  A farmer converting to
organic discovered some weeds disappeared when they stopped using Roundup [!].
[ kandmhfarm on sanet-mg sustainable agriculture email list 4 Jun 2000
  http://www.ibiblio.org/london/orgfarm/crops/large-scale.weed-control
  or http://lists.sare.org/archives/sanet-mg.html ]

Of course there are plenty of other types of toxics floating around, as well as
things that are not necessarily toxic but can be significantly disruptive if
there's too much, such as fertilizers, hormones, pharmaceuticals.

Amphibians survived 4 previous mass extinctions over the last 350 million years,
but are now the most threatened major category of creatures, with 1/3 of species
already threatened.  Amphibians have survived a much longer time and through
more drastic environmental changes than mammals have. If they're in trouble
that's an alarm bell warning that conditions have reached a danger point.
If disregarded and not turned around, we're asking to face trouble ourselves
sooner or later.

It's popular to blame problems on diseases, but we'll probably never know
how much the diseases are due to weakened immunity caused by toxic disruption,
and/or disruption (including by chloramine) of beneficial bacteria, fungi, and
other micropredators and competitors that keep the pathogenic ones in check.
(This also applies to people; for example diabetes has been linked to toxics,
not to fats.  Many are fooled into thinking fats are bad because many toxics
concentrate in fats. If anyone knows of a single other study that separates out
whether it's the fats or the toxics I'd like to know.)
But then it's also unlikely there's any one single factor, it's more likely
there are just too many negative factors for them to deal with all at once.

Except for Relyea, the authors of the studies referenced below are at UC
Berkeley and SF State. You could try asking them your questions, and you may be
able to get them or their students interested in studying Sausal's frogs, though
it would be impolite to impose on them without first reading what they've
already published and it would be a good idea to get up to speed on the subject
in general. I came across another article by one of the authors at
http://www.pnas.org/content/104/20/8201.full

While people are the cause of a lot of the problems and it's understandable to
be drawn to pristine areas, I believe people can also be the cause of solving
the problems, and overlooked opportunities for conservation are to tap the
large pool of people-power available in urban areas, which has the potential
if done right to turn things around faster and more economically there than in
rural areas, even if starting from more degraded conditions.  Urban areas can
also be laboratories for trying different strategies to find out what does and
doesn't work, which can then be used to achieve greater effectiveness in larger
remoter areas.

references:

Are we in the midst of the sixth mass extinction? A view from the world of
amphibians, David Wake, Vance Vredenburg,
Proceedings of the National Academy of Sciences v105 suppl 1, Aug 2008,
http://www.pnas.org/content/early/2008/08/08/0801921105.full.pdf
This is the full article the page you mentioned was referring to.

The lethal impact of Roundup(R) on aquatic and terrestrial amphibians.
Relyea, R.A., Ecological Applications 15:1118-1124 2005

The lethal impacts of Roundup and predatory stress on six species of North
American tadpoles,  Relyea, R. A., Archives of Environmental Contamination
and Toxicology 48:351-357 2005

The impact of insecticides and herbicides on the biodiversity and productivity
of aquatic communities, Relyea, R. A., Ecological Applications 15:618-627 2005

For details see http://www.pitt.edu/~relyea/Publications.html and its link to
abstracts and reprints. He also has articles in press on pesticide mixtures,
lethal effects of "sublethal" amounts of pesticides, and "Interactive effects of
predators and a pesticide on aquatic communities" which I haven't seen but
intriguingly appears to suggest the possibility that trout plus pesticides could
doom the frogs while either alone might not.

Hermaphroditic, demasculinized frogs after exposure to the herbicide atrazine at
low ecologically relevant doses, Tyrone Hayes etal,
Proceedings of the National Academy of Sciences v99 i8 p5476(5) 16 April 2002
http://www.pnas.org/content/99/8/5476.full.pdf

Atrazine-Induced Hermaphroditism at 0.1 PPB in American Frogs (Rana pipiens):
Laboratory and Field Evidence, Tyrone Hayes etal,
Environmental Health Perspectives v111#4, April 2003,
http://www.ehponline.org/members/2003/5932/5932.html

Pesticides and Flawed Frogs, Carl Hall, SF Chronicle 9 Jul 2002
http://www.mindfully.org/Pesticide/2002/Flawed-Frogs-Pesticide-Deformed9jul02.htm

>I've lived on Sausal Creek at the end of Hickory Street since 1990, 
>and I'm quite concerned by the fall-off in Pacific chorus frogs in 
>the past couple of years.
>
>During the 1990s, the pattern was that you could hear a few frogs 
>here in March and April, a strong chorus in May, June, and July, and 
>then none by mid-August.  Starting in 2000, you could hear the first 
>frogs earlier in the year, in February and even late January.  During 
>2006, 07, and 08, there have been only a few frogs to be heard all 
>summer, and fewer with each successive year.  It's my impression that 
>the fall-off started a year or so earlier a bit upstream, at the 
>Woodbine/'Pleasant stretch of the creek.
>
>I just read 
>this: 
>http://www.berkeley.edu/news/media/releases/2008/08/12_extinction.shtml 
>but don't know whether any of it is relevant to local 
>conditions.  I've wondered whether our rising trout population is 
>contributing to the decrease in the frog population.  Or could it be 
>chloramine from our water supply that has made its way into the 
>creek?  Global warming?  Any theories?
>
>Janet Broughton




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