Froggies: Good News for the Sierra

[gdurkee]

Hi folks. It's been awhile since I've logged on but thought I'd post a recent article on recovery of the Mountain Yellow Legged Frog (YLF) recovery effort:
https://www.usatoday.com/story/news/nat ... 331174007/

I worked as a backcountry ranger in Sequoia Kings when much of the initial research and effort was happening and every aspect of the story is incredibly cool. Probably many here "of a certain age" remember hiking in the Sierra along a lake or stream shore and seeing hundreds of frogs plop into the water ahead of them. This was true until the early 80s in many places throughout the Sierra.

Starting in the mid-80s, YLF populations started disappearing -- or maybe it was only noticed for the first time. The initial reason was fish, though I don't know why there was such a dramatic disappearance noticeable then. Fish had been in the high Sierra since their introduction starting in the 1880s or so and then expanded by both informal "coffee can" introduction and, then, more formal planting by CA fish & game (now Department of Fish & Wildlife). After the glaciers, fish couldn't get past the waterfalls on the major river systems and were, effectively, not present above ~7,000' through much of the central and southern Sierra.

Anyway, the non-native fish eat both the tadpoles and adult frogs. The population loss of yellow-legged frogs was noticed by NPS biologists in the 80s when some surveys started specifically looking for them. Several researchers, including Roland Knapp mentioned in the article and Vance Vredenberg fairly quickly showed that fish were the main cause of the YLF disappearance in what turned out to be a huge extent of their former range (from memory, I'm thinking 70% but that could be off by quite a bit...).

In 60 Lakes Basin (while I was working at Rae Lakes) Vance ran a net down a small lake, removed all the fish on one side and, literally within days, there were frogs back from nearby fishless lakes (about a mile away). This showed that froggies were constantly on the move and that the fish would get them quickly when they got to a lake with fish. Also, of course, any tadpole eggs they laid were immediately eaten. Small exception was if the water was too shallow for fish as was the case at the NW end of Bullfrog Lake in some years.

What was fairly amazing (for a bureaucracy like the NPS) is, within 2 years, they put together a plan to remove fish from a number of lakes to reestablish the native frog populations. So NPS in Yosemite and Sequoia Kings started a program in some -- but only some -- lakes to remove fish, allowing the froggies back. It worked and the Yellow Legged frog was, once more expanding into it's former range.

But then, bad news!, a fungus -- Chytrid -- that had already been decimating the red-legged frog of the foothills was moving upslope and, by the 90s, was affecting the YLF populations and wiping out thousands over the next 20 years. Chytrid reached 60 Lakes Basin by the early 2000s and was decimating the previously health YLF population there. In my time in Sequoia Kings, I watched Chytrid completely wipe out YLF frog populations in Dusy Basin, Upper Whitney Creek, and Kearsarge Basin (though, in 2010 or so, I found a teensy population surviving in a small tributary of Bullfrog).

So, while the fish removal and reintroduction of YLF was darned successful, the problem was now Chytrid wiping out all the populations.

But back to good news! Roland, Vance and a bunch of other dedicated froggie researchers starting finding occasional frogs that survived, out of the thousands who'd died. They were resistant to the fungus. Taking them back to labs and breeding them, then reintroducing them to lakes that had been decimated is now, apparently, working. the Mountain Yellow legged frog is coming back yet again!

As many of the stream ecosystems are restored to what they were pre-fish, we're also seeing a return of insects (fish aren't eating the larvae) and birds now returning to get the insects around those lakes and streams.

I know there's been quite a bit of unhappiness by fishing-folk here that their favorite fishing places might be eliminated. I just noticed The Fishing Hole has a long thread on what lakes are affected. When I left Sequoia Kings (trashed my hip...) no lakes with what I considered "good fishing) (e.g. goldens over 12" or so) had fish removed, though maybe that's changed (??).

Anyway, I gotta say as a person long-interested in and supportive of restoring, as closely as possible, a pre-European ecosystem in the National Parks, I"m pretty happy with this success as well as the combination of reasearch and planning implementation that made it happen. It joins other restoration successes such as Peregrine Falcons, Condors, Bald Eagles & etc. in a little good news for critters and ecosystems.

[wildhiker]

Great news. I don't think I've ever seen one of the yellow-legged frogs in the High Sierra. I've heard frogs in some places, but this article says they are tree frogs. I look forward to someday seeing the yellow-legged frogs.
-Phil

[swimjam]

Gdurkee, thank you for sharing this fascinating story.

[paul]

I recall being at a llittle unnamed lake south of Pinchot Pass in 1993, and there were so many little frogs in the grass that it was nearly impossible to get to the shore of the lake without stepping on a frog. Would those have been YLF's?

[gdurkee]

Paul: Hi. Those were probably Tree Frogs -- now the Pacific Chorus Frog. They're small, have a blackish band across the eyes, and often emerge from lakes at about the same time. Unlike the Mountain Yellow Legged, they don't necessarily stay in or near water as adults and grow to maybe the size of a large thumb. Oh, they're also the ones you might hear ribbeting -- you very rarely hear the YLF. They do it underwater or occasionally in the shallows and their call is more a high pitched squeak.

Phil: Yeah, they've been a rare siting but, with luck, sounds like a lot more places you'll be able to come across them in numbers like the "old days." If you get into 60 Lakes Basin I think they're probably pretty well established at most lakes there by now (one of the first study areas); some of the ponds in upper Dusy Basin. Unfortunately, it's been awhile since I've been in -- or kept up with -- the recovery efforts in Sequoia Kings or Yosemite. Perhaps others here have run across them more recently... .

Anyway, a cool sight if you find them and a teensy sign of a recovering ecosystem.

[LMBSGV]

As someone "of a certain age" who fondly remembers the "frogs plop into the water ahead of them," this was a wonderful post to read. With all the transformations taking place due to climate change in the Sierra, it's good to know there is something positive occurring.

[Harlen]

Nice to have you back George. Thank you for the positive update on the native frogs. I too would love to have more frogs about. I have had the luck to run into them in the lakes of Center Basin, where I also met two of the researchers working on the project. I think it was at one of the smaller lakes by Golden Bear Lake where I had the experience of a lakeshore lined with hundreds of Yellow-legged Frogs. As I walked slowly by, they would leap about 1.5 meters out into the lake, and then just stay there in place, with their long legs stretched out. I believe it was in this beautiful lake:

[creekfeet]

Harlen- A few years back I camped at the lake shown in your photos, and there were hundreds if not thousands of frogs lining the shores, and swimming around. It was one of, if not my favorite wildlife experience in the Sierra. The little buggers just have so much personality, and are pretty massive when swimming and fully extended. I hope their range continues to expand back to their pre-trout peak.

[gdurkee]

Ah, memories! I was sitting at that lake in the top photo with a Heron standing at one end, then a coyote scurried by following a deer, and a golden eagle overhead. Very cool place. And, oh yeah, froggies.

I left Sequoia Kings as Chytrid was wiping out froggies and some of the resistant ones were taken back to labs to breed. This effort started in Yosemite in 2013, my last year in Sequoia and mostly I think (?) was moving surviving/resistant frogs moved to other population habitats within Yosemite.

Other methods were being tried too -- actually washing infected frogs with a anti-fungal solution -- the fungus attacked the skin which was their primary infection barrier. The young frogs died very quickly. The theory was that would give them enough time for their immune system to take over. I don't know if it was successful and, in any event, was only a holding action to save the existing populations

Another side note: the populations that did survive -- though much reduced -- were mostly those where fish had been removed in the previous ~10+ years. By removing fish within a basin, the frogs were able to expand their population to nearby lakes so, when chytrid hit one lake, the other lakes still held populations. Also, the populations were hight enough that, statistically, some would be resistant. There were even grants from public health to study the spread, contributing to models used in diseases among humans.

Anyway, that was all happening as the resistant frogs were being taken from surviving lakes as well as increased in labs and zoos.

Here's Knapp et al's paper: https://www.nature.com/articles/s41467-024-53608-4

[Jim F]

Four years ago (7/29/2020) I passed southbound through Center Basin and over Junction Pass. My written notes for that day include, "Gill nets noted in the lower lakes, including Golden Bear Lake." It was late afternoon and no frogs were noticed. Awesome that things are turning around. THANKS to those who had the wisdom and took the effort to make this happen.

A couple years earlier (just relying on memory here), I was descending Le Conte Canyon from Muir Pass on the JMT. At the lake (about 11,000') on the left about a mile below the outlet of Helen Lake, I observed a half dozen people scattered along the shore. They seemed to be involved in some scholarly activity. They were!-capturing garter snakes. But they said their primary interest was frogs.

In the field these researchers gently manipulated the snakes to induce regurgitation of gastric contents. Were there frogs in the stomach contents? That was the focus.

My primitive understanding is that in the High Sierras the fates of the garter snake and frog are significantly related. Perhaps someone on the HST Forum can expand here, assuming my understanding is not completely erroneous.

Jim