Another Field Season......

Well, the field season is over for another year. I've been doing amphibian-related field work in the High Sierra for almost 20 years now, and I can't remember a summer as weird as this one was. In mid-July, high elevation lakes were still frozen solid. Summer finally arrived at the beginning of August, but in early September I found myself in a backcountry snow storm. As I hiked through a blizzard of swirling white, all I could think was, "What?! Already? Summer has just started!". And for the past couple of weeks, the blue skies typical of early fall in the Sierra have instead been leaden skies portending of thunderstorms. What the heck? 

In my absence from the front country, lots has happened in the world of frog conservation. Most importantly, perhaps, was the die-off of more than 100 mountain yellow-legged frogs being housed at Fresno's Chaffee zoo. The cause of death remains a mystery. These frogs were collected in southern California as part of an effort to establish another captive breeding colony, the progeny of which could eventually be released back into the wild. This incident should serve as an important reminder of how difficult it is to maintain healthy frog populations in captivity. Whenever possible, I'd like to instead see concerted efforts to establish frog populations in suitable natural habitats across the range of the frog. Populations of the mountain yellow-legged frog have tremendous reproductive potential, and under the right conditions could produce lots of offspring for reintroduction to additional sites. And those offspring would come at a fraction of the cost of those from captive rearing facilities. The fact that fewer than 200 adult mountain yellow-legged frogs exist in southern California limits the options available, but I worry that the current focus on captive breeding has distracted us from a broader approach that includes trying to establish additional wild populations. 

The U.S. Fish and Wildlife Service (USFWS)-led effort to develop a Conservation Strategy for Sierra Nevada populations of the mountain yellow-legged frog continues apace. This effort is still in the information-gathering phase and I expect that a draft strategy won't be released until sometime in 2012, perhaps around the time that the USFWS begins the process of deciding whether these Sierra Nevada populations should be listed under the federal Endangered Species Act. In addition, the California Fish and Game Commission will soon be meeting to decide whether to list mountain yellow-legged frogs across their range under the California Endangered Species Act. And then, both Yosemite and Sequoia-Kings Canyon National Parks continue to work on their respective park-wide aquatic restoration plans, plans that will likely propose multi-decade efforts to remove nonnative trout from key frog habitats within these jurisictions. I expect that both parks will release draft plans in 2012. 

So, 2012 looks to be a busy year. Stay tuned for updates....

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Always Something New to See

One of the greatest things about my job as a field biologist is the chance to see amazing things happen in the natural world. I see fascinating stuff every day while out in the mountains, but some happenings are truly memorable. In the past, that has included seeing bears swimming in Sierran lakes, Clark's Nutcrackers eating tadpoles of the mountain yellow-legged frog, water shrews diving for food in alpine lakes, and a deer swimming in a lake to escape two coyotes intent on a late October meal. That strategy by deer of jumping into water to escape predators seems to be one that they use fairly regularly, but I've never seen other animals do the same. Until this week. 

I was in the southern Sierra Nevada doing my usual things, this time paddling around a lake to measure its maximum water depth. On this spectacular day in the mountains, I was staring at the world around me while paddling to what looked to be the deepest spot. I slowly became aware of a squeaking sound coming from somewhere in the surrounding foxtail pine forest. As the sound got louder I looked more carefully into the forest's shade. Suddenly, out of nowhere came a pika running at full speed parallel to the lake shore, with a weasel close behind. The weasel was closing fast on its prey when the pika suddenly turned toward the lake and to my amazement dove in. It then swam furiously out into the lake but the weasel stayed on shore, staring at the pika and at me. Apparently realizing that the weasel was no longer in pursuit, the pika turned to swim parallel to shore and after a minute or so of that, headed to shore in earnest. I was sure the weasel would run along the shore and grab the pika as it approached land, but instead the weasel turned and ran off into the woods. As soon as it hit the shore, the pika did the same but in the opposite direction. 

Swimming pikas?! Who knew?

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Out in the Field Again, Finally!

It has been a long winter here in the Sierra Nevada. This "spring" was one of the coldest and wettest on record, and as a consequence the higher portions of the mountains are still blanketed in snow. But now that the melt has finally begun in earnest, my field season is fast approaching. Last week I hiked into the Golden Trout Wilderness to have a look at a particularly important population of the southern mountain yellow-legged frog (Rana muscosa). This population is the furthest south R. muscosa population left in the Sierra Nevada. Populations historically occurred as far south as Breckenridge Mountain in Kern County, and included large populations in the montane and subalpine meadows along the South Fork Kern River and Golden Trout Creek. As far as we know, those are all gone now, and this population that I visited is the last hold-out in this southern portion of the historic range. 

The fact that this population is still extant is remarkable. Most of the meadows in the Golden Trout Wilderness have been badly degraded by intensive sheep and cattle grazing in the late 1800s and early 1900s that resulted in channel incision and lowered water tables. As a consequence, many of the ponds and other amphibian habitats disappeared. In addition, California golden trout (that were native to much of the South Fork Kern River watershed) were moved into the few naturally fishless lakes and streams that existed in the area, further reducing habitat for R. muscosa. And then probably sometime in the 1970s or 1980s, the amphibian chytrid fungus (Batrachochytrium dendrobatidis) swept across the region, further decimating R. muscosa populations. 

Despite all of these changes, this population of frogs somehow hung on. But for how much longer into the future they will remain is an open question. This R. muscosa population is centered on a single small breeding habitat, an abandoned stream channel filled with sedges and fed by seepage from the adjacent stream. When the stream someday moves back into this channel (as it inevitably will), the only breeding site will be gone and so too will be the frogs. As such, it is imperative that frogs from this population be used to reestablish populations in suitable habitats elsewhere in the vicinity. Based on the low success rate of developing new mountain yellow-legged frog populations, this won't be an easy task. But without such an effort, the range of R. muscosa will continue to contract until this once abundant species is all but gone from its former haunts.

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Captive Breeding Yields Another Round of Eggs

The Los Angeles Zoo is reporting that their technique of holding frogs at cold temperatures over the winter followed by a gradual warm-up in the spring  resulted in another batch of egg masses being laid in March. These egg masses subsequently hatched into hundreds of tadpoles that will be released into the wilds of southern California later this summer. For more information, check out this story. 



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New Insights Into the Cause of Recent Amphibian Declines

During the last decade, Karen Lips and colleagues have documented the spread of the amphibian chytrid fungus (Batrachochytrium dendrobatidis: "Bd") southward through Costa Rica and Panama, and its devastating impacts on amphibian populations. However, it has remained unclear whether Bd was also the cause of declines in areas north of the region studied by Lips et al., including Mexico, Guatemala, and the Monteverde region of Costa Rica. Throughout this region, a host of amphibian species either disappeared or markedly declined in the 1970s and 1980s, and the cause of these declines and extinctions has until now been largely speculative. 

In a new study published this week in the Proceedings of the National Academy of Sciences, Cheng and colleagues used museum specimens collected in Mexico and Central America during the period 1967-1987 to test for the presence or absence of Bd. Their results provide compelling evidence that since the 1970s Bd has been spreading south through southern Mexico and Central America (red dots with stars in figure). This timeline dovetails nicely with that for Costa Rica and Panama posited by Lips et al. (red dots in figure). Across their study sites, Cheng et al. also show a repeated pattern of Bd being absent from amphibians collected in the early years of their analyses followed by initial detections of Bd and the coincident decline of multiple amphibian species. 

So, it is now quite clear that Bd was a major cause of enigmatic amphibian declines that occurred in this region during past decades. The molecular technique developed by Cheng et al. to detect Bd on preserved museum specimens should open the door to a host of future Bd-related studies that take advantage of additional preserved amphibian specimens stored in museums around the world. I suspect that these specimens have many a tale to tell regarding the global spread of Bd and its impacts on amphibians. 

Further reading:
Lips, K. R. 1998. Decline of a tropical montane amphibian fauna. Conservation Biology 12:106-117.

Lips, K. R. 1999. Mass mortality and population declines of anurans at an upland site in western Panama. Conservation Biology 13:117-125.

Lips, K. R., F. Brem, R. Brenes, J. D. Reeve, R. A. Alford, J. Voyles, C. Carey, L. Livo, A. P. Pessier, and J. P. Collins. 2006. Emerging infectious disease and the loss of biodiversity in a Neotropical amphibian community. Proceedings of the National Academy of Sciences, USA 103:3165-3170.

Lips, K. R., J. R. Mendelson III, A. Munoz-Alonso, L. Canseco-Marquez, and D. G. Mulcahy. 2004. Amphibian population declines in montane southern Mexico: resurveys of historical localities. Biological Conservation 119:555-564.

Rovito, S. M., G. Parra-Olea, C. R. Vásquez-Almazán, T. J. Papenfuss, and D. B. Wake. 2009. Dramatic declines in neotropical salamander populations are an important part of the global amphibian crisis. Proceedings of the National Academy of Sciences 106 3231-3236.

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Mitigating the Effects of Chytridiomycosis - Part 2

Chytridiomycosis is the disease of amphibians caused by the fungal pathogen, Batrachochytrium dendrobatidis. Given the severe impacts of this disease on the world's amphibian biodiversity, there is a lot of interest in mitigating these impacts to the extent possible. I wrote about some of those efforts in a previous post. Doug Woodhams and colleagues have just published a paper that reviews the progress made to date in this important field (pdf). Having been involved in research that tested some mitigation strategies, I suspect that it will be quite a while before we have effective mitigation measures that can be effectively applied in the wild. 

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With Spring Come New Frog Reintroductions

On April 14, biologists from the USGS and the San Diego Zoo released another batch of Rana muscosa egg masses that were laid in captivity. This effort is part of an effort to breed this endangered species in captivity and reintroduce the progeny into the wild in southern California. For more information, check out this link. This reintroduction effort was begun last year and I'm curious to hear the results of last year's egg mass reintroductions. With any luck, there should be some second-year tadpoles swimming around out there this year. 

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