October 18, 2009

Another Field Season has Come and Gone

My 2009 summer field season ended in late September. Now weeks later all of the research gear is put away and the data is safely in my lakes database. The summer went largely as expected, with some notable successes and some unanticipated challenges. Below I've provided a summary of what our summer objectives were and what we actually accomplished. But first a sad note....

This summer I lost a close friend and fellow field biologist. On August 30, Jeff Maurer died in a climbing accident while ascending Third Pillar on Mt. Dana. Jeff had worked in Yosemite National Park since 1988, studying Peregrine Falcons, Great Gray Owls, and Northern Goshawks. In 2006 he took on the task of leading Yosemite's new lake restoration program, and in that capacity he directed fish removal efforts in numerous key locations around the Park. These efforts will continue, of course, but Jeff's infectious enthusiasm and unmatched dedication to this restoration effort will be sorely missed. He was truly one-of-a-kind. For stories about Jeff, check out http://yosemite-jeffmaurer.blogspot.com/.

So, what did we set out to do this summer? Our research team (me, Cherie Briggs, Vance Vredenburg, Erica Rosenblum, and more than a dozen field and laboratory assistants) had two primary objectives. The first objective follows from our field observations that after the arrival of the
amphibian chytrid fungus (Batrachochytrium dendrobatidis - "Bd") at a site most mountain yellow-legged frog populations decline to extinction but a few persist despite the disease, albeit at markedly lower densities. There are several potential explanations for these different disease outcomes, including inherent differences in frog susceptibility to chytridiomycosis (the disease caused by Bd) or differences between Bd strains in their virulence. So this summer we conducted a laboratory experiment to evaluate the relative roles of these two factors in driving different disease outcomes (frog population persistence versus extinction). We hope to wrap up the experiment by December.

Our second objective was to use a field experiment in which mountain yellow-legged frogs are cleared of Bd to determine whether this treatment influences the outcome of Bd epidemics. Frogs were treated with an anti-fungal drug at three lakes in each of two basins located in Kings Canyon National Park. Frog populations in both basins had suffered catastrophic declines in the past four years following the arrival of Bd, and without intervention it is likely that these frog populations would have been extinct within another couple of years. It will be 1-2 years before we have any definitive results but for now, suffice it to say that we were able to significantly reduce Bd loads on frogs in the field and this treatment dramatically improved frog survival. I'm hopeful that such frog treatments may provide us with an important conservation tool in the future, but we still have lots of unanswered questions that need to be addressed. I'll provide further updates as the results come in.

Finally, the California Dept. of Fish and Game (CDFG) released a draft fish stocking EIR/EIS to the public on September 25 (available from the CDFG web site). Comments on the draft document are due to the CDFG by November 16. Given that this document will guide CDFG fish stocking practices for many years I encourage everyone interested in this issue to read the EIR/EIS and provide comments to the CDFG. I'm still working my way through the 8 chapters and 12 appendices but it is clear that there is lots of room for improvement. I'll provide additional details on this document in upcoming blog posts. Stay tuned....

Now that I'm back behind my desk I'll be posting new Frog Blog entries every Monday morning. I hope you find them interesting and informative.

Back to The Mountain Yellow-legged Frog Site.


  1. Re, last paragraph: Great!

  2. Thanks for the update, Roland.

    Sorry about Jeff. I knew that pic of the lake looked familiar. Virginia in Yose.

    I hope you get good results on the Bd treatment.

    Given the lake restoration in Yose, what is happening in those lakes, in terms of ongoing research?


  3. Hi Russ. At the restoration lakes Park staff and I are conducting frequent amphibian surveys to evaluate how the fish removals are affecting frog populations. I'm also interested in collecting invertebrate samples from low elevation fish removal lakes (we've already described post-fish removal recovery in high elevation alpine lakes) but that hasn't happened yet due to a lack of funds.