October 18, 2010

An Unnatural Quiet

This summer I returned again to one of the Sierra's most remote lake basins to resurvey the amphibian populations there. This basin holds a special place in my heart due to its spectacular beauty, isolation, and at one time, an incredible Sierra Nevada yellow-legged frog population. The first time I visited this basin was in 1997 when my assistants and I conducted our initial surveys of its frogs, fish, and invertebrates. Back then, the sheer number of frogs was overwhelming. 

I remember counting 10,000 tadpoles in a single lake. The frantic swimming of these tadpole masses at my approach turned the tranquil water surface to a muddy froth. Adult frogs seemed to occupy every possible bit of water; nearly every lake, pond, stream, and puddle was full of them. As I walked along one lake shore, a frog dove off of a damp ledge ten feet above my head and with legs splayed wide splashed into the water at my feet. The abundant bears in this basin seemed just as fond of the frogs as I was. In several spots where tadpoles aggregated by the thousands, I saw where bears had waded out into the water to catch them. One evening I watched a Clark's Nutcracker land at the waters edge and spear a tadpole. With the tadpole in its beak it flew to a nearby snag, snipped off the tadpole's tail, and fed the body to a begging fledgling. Transfixed, I sat down and watched the show repeat itself several more times. When the adult and fledgling had flown away I walked to the snag and saw that the branch the fledgling had been perched on was covered with 50 or more tadpole tails, some dry and shriveled, some still wet. What an incredible web of life these frogs were a part of!

Back then the world was unaware of the amphibian chytrid fungus (Batrachochytrium dendrobatidis - "Bd") and its devastating effects on amphibians around the globe. I took it for granted that given the paucity of trout in this basin the frogs would always be there, for the bears, for me. A few years later Bd arrived in the basin, causing the collapse of one frog population after another. Within five years the frog numbers had decreased by 95% but I still held out the hope that maybe a few would survive to repopulate the lakes. 

Our resurveys this summer showed that even that modest hope was too optimistic. Most water bodies were now entirely frogless. A few contained only a single adult frog. We found some tadpoles, but too few to give us much hope that the population would still be there the next time we did our resurveys. 

Sitting on a lakeside boulder eating my lunch in the summer sun, I couldn't help notice how quiet the basin had become. No more frothing masses of tadpoles. No frogs jumping into the water by the 10s and 100s in front of me as I walked along the shoreline. Bear sign, once so common, was far less in evidence, although I did see one set of bear tracks that went into the lake where a few tadpoles still basked in the warm shallows, but the paucity of animals would hardly have made a snack much less a meal. No Clark's Nutcrackers eating tadpoles. The mayflies, caddisflies, and beetles were still there, but the once-dominant frogs and the web of life they once supported were gone.

When I first happened upon this place it was defined by the frogs, frogs as predators, frogs as prey, frogs as inhabitants. Now it was different. In the span of less than a decade, a shangri la had become a place of ghosts.

Back to The Mountain Yellow-legged Frog Site.


  1. Roland,
    Thank you for posting this story... What can we do to get the word out more than we are now, so the public will understand how desperate the situation is?
    We'd love it if you would guest post on our blog, Frogs Are Green.
    Meanwhile I'm going to post a link to this on Facebook.
    Susan :)

  2. Hi Susan. I don't know that we can do much more than we are already doing to inform the public about the amphibian decline crisis. In today's hyperlinked world, people's attention spans are shorter than ever, especially if the information isn't particularly uplifting. We just need to keep plugging away at this, each in our own way.

    Thanks for the offer to guest post on "Frogs are Green". However, I'm afraid that with all of my obligations as a researcher I can barely keep up with this frog blog much less post elsewhere. Sorry.