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Scientist: Frog's decline threatens Sierra ecology
Posted: Sun Feb 05, 2006 9:31 am
http://www.mercurynews.com/mld/mercuryn ... 797551.htm
Posted on Sun, Feb. 05, 2006
Scientist: Frog's decline threatens Sierra ecology
By Juliana Barbassa
YOSEMITE NATIONAL PARK - The mountain yellow-legged frog has survived for thousands of years in lakes and streams carved by glaciers, living up to nine months under snow and ice and then emerging to issue its raspy chorus across the Sierra Nevada.
But the frog's call is rapidly going silent as a mysterious fungus pushes it toward extinction in its remaining refuge in national parks.
``It's very dramatic,'' said Lara Rachowicz, a Yosemite biologist who is leading an effort to save the tiny creature. ``One year, you visit a lake and the population will seem fine. The next year you go back, you see a lot of dead frogs scattered along the bottom of the pond. In a couple years the population is gone.''
There are about 650 populations left in Yosemite, Sequoia and Kings Canyon national parks, but most lakes have only one to five frogs -- not enough to guarantee their survival -- and 85 percent of them are already infected with the lethal fungus.
At one time, the frogs were so thick that tadpoles frothed shallow waters, and it was hard not to step on a frog on shore.
Their decline started when trout were stocked in Sierra lakes -- first carried in buckets by mule and then dropped by plane -- to supply fishermen. The voracious fish, which are still being introduced into the high Sierra outside park boundaries, are leaving only isolated groups of the frogs scattered over widespread lakes as high as 13,000 feet.
Despite living within the protective borders of some of the nation's most beloved parks, the remaining frogs can't resist the onslaught of the fungus and can't travel far enough in trout-infested streams to repopulate areas devastated by the fungus.
For the past five years, they've been disappearing at a rate of 10 percent a year, Rachowicz said at a gathering last month of 24 experts trying to save the frog.
The chytrid fungus, which has been linked to the extinction of amphibians in places as far away as Australia and Costa Rica, kills the frogs by growing on their skin, making it hard for them to use their pores and regulate water intake. The frogs die of thirst in the water, Rachowicz said, pointing to a photograph of an emaciated frog floating belly up in a shallow pool.
In a handful of years the frogs may be gone, leaving the high-elevation lakes in silence, and snapping the local food chain.
``There would be an unraveling of that web of life, because this species plays such an important role,'' said Roland Knapp, a research biologist with the Sierra Nevada Aquatic Research Laboratory.
The frog's disappearance would affect about 300 species in the rugged high country, from the insects they prey on to the garter snakes and coyotes that eat them, said Knapp, who led a survey counting the frogs in more than 6,500 bodies of water in the parks in 2000-02 and 2005.
What's frightening about the fungus's attack on amphibians is that it kills them quickly even in untouched habitats, scientists said.
``It's a mass extinction in the making,'' said J. Alan Pounds, main author of an article in the January issue of Nature that linked global warming to the fungus first named by scientists in the late 1990s.
Amphibians are facing an ecological disaster on a global scale. The Global Amphibian Assessment, a worldwide collaborative survey by hundreds of scientists completed in 2004, found that one-third of the world's 5,743 amphibian species are threatened and 168 are possibly extinct.
``I suspect that climate change is involved in general in these enigmatic declines,'' Pounds said. ``Ultimately, we have to have a transition to cleaner energy technologies, to cleaner sources of energy. But by then, it might be too late for the mountain yellow-legged frogs.''
Posted: Sun Feb 05, 2006 10:04 am
I could easily be wrong but this sounds like hyperbolic, agenda-driven science to me
Posted: Sun Feb 05, 2006 11:28 am
LOL! Global warming is to blame for a fungus? Does anybody else find it a little more than coincidental that this fungus started wiping out the frogs about the time the do-gooders started to "de-fish" the lakes to save the frog? Hmmmm...maybe they introduced the fungus by accident and they are trying to blame it on global warming.
Posted: Sun Feb 05, 2006 4:42 pm
Every time someone posts one of these trout eat frogs hypotheses I have to respond that such is mostly nonsense with scant reality. All along, I've suspected those biologists that are putting forth such ideas have another agenda. My reasoning is that there are many small ponds and stream where frogs exist that are too small or warm for trout. And there are many marshy meadow areas with springs even late into the fall that always seem to have healthy frog populations. Also in many lakes that do have trout, I regularly see lots of tadpoles. That is in part because there are shallow areas along the shores of most lakes where fish cannot manuever. In fact tadpoles sem to prefer the shallow edges I suspect because they like the warmth. While it is certain there are likely some lakes where the species of fish resident have learned to enjoy an amphibian diet, I doubt the general demise of frogs has much to do with it. Far more likely is the climate, and things like that fungus. It may be that the fungus has in fact been introduced into the Sierra mountain environment as a result of man's global activities. Tremendous damage has already been the result of man's global transport of alien species into what were historically biologically isolated environments. ...David
Posted: Sun Feb 05, 2006 10:59 pm
Well, it's useless with you guys, but anyone else who hasn't can check the map of frog decline at:
About half-way down the page. The red dots are where frogs were known (mostly within the last 20 years) and haven't been found in the last several surveys. Roland Knapp (in the article) has had teams out checking literally every lake in the Sierra. Those are his results.
You're right about the tadpoles liking the shallow shelves. A few do survive because the fish can't get there. But there just aren't that many lakes like that. Also, when they're adults, they need the deeper water to winter over. If there's fish, they get the frogs. Always. No exceptions.
There is no question -- none -- that non-native fish have played a major role in the extinction of native frogs in the Sierra. Chytrid is likely finishing them off. Look, I live and work there and have done so for 35 years. I spend about 4 or more months a year in the backcountry -- 7 days a week, 24 hours a day. I actually see this happening. It is beyond me how you guys can come up with these statements -- based on what? A few trips a year and not even reading the reports these "hypothesis" are derived from?
Read the reports. Go out to the lakes that still have frogs. Compare them to the lakes that don't. Go back the next year. And the next. And the next. Go back in 10 years. Bring back a list of where you find frogs and fish together; where you find frogs but no fish. Both Vance Vredenburg and Roland Knapp have decades in the backcountry studying this one problem. Read their stuff. Do it yourself, you'll get the same results.
Posted: Mon Feb 06, 2006 9:35 pm
I have to second G. Durkee's statement above. The amount of data compiled over the years by researchers on frog populations in the Sierra is overwhelming. This research has been published in peer-reviewed scientific literature in multiple articles and it is not of the same ilk as any old statement that can appear on the web or any statement that can be made to the print or TV media, regardless of source.
As a dedicated fisherman (have personally fished over 600 different backcountry lakes in Sierra), I can see that many fellow anglers have been up and arms about the frog issue, and I think part of the problem with this issue is the lack of information that many anglers have when they emotionally stride into this. I think the big debate now is over what we should do about the situation--it shouldn't be over the validity of the frog decline data. There are some serious questions from a fisheries policy standpoint and I'm not convinced the best proposals are the ones that have been brought to the table, let alone adoped as policy. However, other anglers need to more carefully research the background data before they dismiss it as an anti-fishing conspiracy. We will get nowhere with that approach. I myself have spent 40 years in the Sierra backcountry and I've also seen the frogs vanish at places that used to have them. One can also read historical accounts, the most striking being McDermand's fishing books and you can't help noticing all those accounts of obese trouts gorging themselves on polliwogs.
That trout harmed MYL frog populations is pretty robustly demonstrated by the distribution of trout-bearing vs frog bearing lakes. And yes, ALL lakes of the Sierra have been sampled for frogs and trout--ALL of them. The database is exceptionally large (1000's of lakes). Whether getting rid of trout will bring MYL frogs back, or even help is open to question now because of the fungus. And this is where I think the big debate lies with respect to future fisheries management. There also seems to be a curious altitude/latitude or temperature(?) dependence on both the coexistence of trout and frogs and apparent susceptibility of the frog to the fungus. There are places in the N. Sierra where frogs have persisted in waters with voracious trout populations that have been there for many decades. I have also heard 3rd hand (but not read the original work) that there is some indication that the frogs in the N. Sierra are not as vulnerable to the effects of the fungus. Certainly this must enter into solutions in some way, if this trend proves real and can be related to some cause.
What we anglers need to do is to keep ourselves informed as we can about the latest studies. There are a number of possibilities open in terms of fisheries management that can potentially benefit both frogs and fishermen, but we won't be able to get the most equitable solution unless we argue from knowledge and data. I would like to see a somewhat more cooperative relationship between eco-systems advocates and high country sportsfishers, such as is much more the case (apparently) in Washington state. Here there seems to be much more coordination between organized wilderness trout fishing groups, Washington's Fish and Game, and various agencies and groups advocating ecologic balance in high lakes. Many of the fisheries management proposals that are discussed there, are, in my opinion, a generation ahead of what we commonly here discussed here. Which leads to another point--there are lessons to be learned from other parts of this country and the world, and we benefit when we learn from them.
Posted: Mon Feb 06, 2006 9:54 pm
Ah, George, thank you as always for injecting some empirical evidence into the fray. Why is it that everyone seems to think they know so much more than the biologists who are actually studying the stuff? Do they really think we're such idiots? Here in Chesapeake Bay country it's well known that if you stake out an area for study, you have to stake it out with buoys that are *never* above the surface (you have to use GPS coordinates and then fish around for the buoys with a boat hook or something). Why? Because the watermen are *sure* that anything we find out will be used against 'em, so if they see anything that looks like a study site they destroy it. Sigh.
On the other hand, it never hurts to ask the watermen (here) or the anglers (there) what they've seen -- they go places we don't always manage to get to...
Posted: Mon Feb 06, 2006 10:28 pm
Solid. I am always much happier dealing with peer review data rather than Rush Spewed data. With the thousands of trout-bearing lakes in the Sierra, it's hard for me to imagine reclaiming more than a couple of hundred of them for frogs over the next 20 years. Seems like a small and reasonable trade-off.
Speaking only of the National Parks, most visitors & fisherfolk are pretty open and supportive of our netting a handful of lakes to reestablish habitat. It is such a major effort to get just a few lakes trout free that it's just never going to expand much in the forseeable future.
There is some evidence that frogs can recover a year or two after a chytrid outbreak. Whether those are the ones who have some level of immunity or the fungus disappears is not really known yet, I don't think. I haven't yet heard of a N/S difference in Chytrid effect, but it's possible. I'll ask next time I see the froggy people.
Anyway, thanks for weighing in with some more facts.
Posted: Tue Feb 07, 2006 1:52 pm
Thanks for those links. Now for the first time I'm seeing some meaningful information. The frog situation is not something I've been paying attention to but rather something that I occasionally see threads on. When the frog surveys began I talked at length to some of them I came across above Onion Valley. At that point it seems none of those I talked with on that survey had much of a convincing argument. I pretty much related my own observations that I see tadpoles in a lot of lakes, marshes, and streams. Thus speculated that something did not make sense and that made me suspect the biologists. It is easy to suspect that some non-fishing people would like to see fish removed from many High Sierra lakes simply because that would remove a significant number of visitors that some obviously might consider environmentally unfriendly. The trash and illegal firepits stuff. One problem in the past is when others have tried to get useful reference information on the web for discussions in such threads all that I'd seen is some watered down newspaper report that did not include much detail other than the fact some bioligists said there was a problem and they were canvassing lakes. Me I kept seeing tadpoles all along. Now from your link, I can see I've been likely mainly looking at Pacific tree frog tadpoles and not the mountain yellow-legged frogs. My own knowledge of many animal species in the Sierra is rather limited and not something I've bothered to ever study deeply so my own opinions have just been loose conjecture. Apparently per your link the tree frogs still do well along the lake edges, in many small streams, and in marshes, while these yellow-legged frogs need deeper lakes to overwinter under the iced over lake surface. Now that makes a lot of sense to me so now you have convinced me thankyou. ...David
Ribbet X 2
Posted: Tue Feb 07, 2006 7:59 pm
Hey, thanks. I didn't even think about the tree frog tadpoles confusing people. You're right, they don't seem to be in trouble and could well confuse some people not looking for the subtle differences. (and, as a side note, they're the ones that go 'ribbet' (kind of). You rarely hear the Yellow-legged).
If you talked to researchers at Onion Valley some years back, that was probably Vance and his gang. It took them a few years to figure it out. Now everyone's working on Chytrid.
I always hate it when artificial differences are set up. As giantbrookie and Bsquared point out, researchers & manager types really need everyone in on the decisions.