Pesticide Harmful to Amphibians is Banned in U.S.

Last week the U.S. Environmental Protection Agency announced that it would ban the use of endosulfan. Endosulfan is an organochlorine pesticide that was developed in the 1950s. Although it is an effective compound against many crop pests it comes with serious health risks to humans and wildlife, including acute neurotoxicity and endocrine disruption. As a consequence endosulfan is banned in more than 63 countries, including the European Union.

Several studies indicate that because endosulfan persists in the environment for years it can be transported long distances from application sites. For example, endosulfan is commonly detected in the Sierra Nevada despite the fact that it is not applied anywhere nearby. The idea that endosulfan detected in the Sierra Nevada originates from applications in upwind agricultural areas is supported by the fact that endosulfan concentrations in the Sierra Nevada correspond very closely with application rates in the Central Valley, with a lag time of 1-2 weeks.

The fact that endosulfan can disperse widely and persist in the environment has long raised concerns about its effects on wildlife. Research on its impacts on amphibians in the Sierra Nevada indicates that endosulfan is detectable in Pacific treefrog populations (Pseudacris regilla) throughout the range and is toxic to amphibians at extraordinarily low concentrations. However, a just-published study indicates that concentrations in frog tissues are generally well below levels that would cause direct or indirect impacts. 

Overall, the effects of endosulfan on Sierran amphibians is likely relatively minor compared to those caused by trout introductions and the amphibian chytrid fungus (Batrachochytrium dendrobatidis). But given its broad toxicity to wildlife and humans the ban on endosulfan use was nonetheless long overdue. 

The following publications provide additional information on the effects of pesticides on amphibians in the Sierra Nevada:

Bradford, D. F., E. M. Heithmar, N. G. Tallent-Halsell, G.-M. Momplaisir, C. G. Rosal, K. E. Varner, M. S. Nash, and L. A. Riddick. 2010. Temporal patterns and sources of atmospherically deposited pesticides in alpine lakes of the Sierra Nevada, California, U.S.A. Environmental Science and Technology 44:4609-4614.

Bradford, D. F., K. Stanley, L. L. McConnell, N. G. Tallent-Halsell, M. S. Nash, and S. M. Simonich. 2010. Spatial patterns of atmospherically deposited organic contaminants at high elevation in the southern Sierra Nevada mountains, California, USA. Environmental Toxicology and Chemistry 29:1056-1066.

Davidson, C. and R. A. Knapp. 2007. Multiple stressors and amphibian declines:  dual impacts of pesticides and fish on yellow-legged frogs. Ecological Applications 17:587–597.

Davidson, C., H. B. Shaffer, and M. R. Jennings. 2002. Spatial tests of the pesticide drift, habitat destruction, UV-B, and climate-change hypotheses for California amphibian declines. Conservation Biology 16:1588-1601.

McConnell, L. L., J. S. Lenoir, S. Datta, and J. N. Seiber. 1998. Wet deposition of current-use pesticides in the Sierra Nevada mountain range, California, USA. Environmental Toxicology and Chemistry 17:1908-1916.

Sparling, D. W. and G. Fellers. 2009. Toxicity of two insecticides to California, USA, anurans and its relevance to declining amphibian populations. Environmental Toxicology and Chemistry 28:1696–1703.

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Otters and Trout in Sierran Lakes: Which Came First?

Despite having spent the last couple of decades hiking around the Sierra Nevada to conduct my research I'd never seen a river otter nor heard much about their presence in the mountains.That all changed a few years ago when a colleague observed a family of five otters swimming across a lake in northwestern Yosemite National Park. The following winter he observed otter tracks along a stream while doing snow surveys in the Park. And then this past summer I found evidence of otters at a lake in northern Yosemite. My curiosity was definitely piqued and I had to learn more. 

Otters are typically described as feeding mainly on fish, and trout are a favorite prey item. So were river otters found historically in the Sierra despite the absence of fish in most water bodies? Or did they expand their range into the Sierra following the introduction of trout into many lakes and streams starting in the mid-1800s? And if they were found in the mountains prior to fish introductions what did they eat? 

Several of us are still trying to answer these questions but the otter sign I found this past summer and some additional information sources we've turned up have provided some intriguing details. First, otters have been reported in the High Sierra for many decades, suggesting that their presence predated trout introductions. Second, some notes recorded by a Yosemite wilderness ranger in the 1970s suggested that otters were eating Sierra Nevada yellow-legged frogs (Rana sierrae). He reported seeing otters in a lake in the Vogelsang area and also found numerous pairs of discarded frog legs around the lake shore. Given how abundant R. sierrae were historically it certainly seems possible that otters could have subsisted on them. And finally, the otter sign that I found this summer was several otter scats atop a lakeshore boulder. I collected the scats and dissected them back in my lab. What I found amazed me. The scats contained dozens of bones of a size and structure that likely makes them those of Rana sierrae adults and juveniles. But the dominant remains in the scats were from aquatic invertebrates, including giant water bugs (Lethocerus americanus), backswimmers (Notonecta sp.), and dragonfly and damselfly larvae (Aeshna and Enallagma, respectively)! Given the relatively large size of frogs their inclusion in otter diets isn't particularly surprising. But invertebrates?? Notonecta are barely an inch long and yet otters were eating them by the dozens.

To return to the questions I posed at the beginning of this story, I'm guessing that otters utilized Sierran lakes prior to the introduction of trout and subsisted on a diet of amphibians, aquatic reptiles, and invertebrates. With the introduction of trout, otters had another food item on their menu. But did this new food item allow otters to increase in numbers? If so, could their elevated numbers be negatively impacting the few frog populations remaining today? I wish I knew. I'd sure love to be able to radio track some of these guys around Yosemite and figure out what habitats they use and get a more complete picture of their diets. 

If any of you readers have observations of river otters in the Sierra Nevada, I'd love to hear about them.

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Do We Have to Exclude People to Save Frogs?

When species are listed under the Endangered Species Act, potential impacts to those species justifiably receive greater scrutiny. In our crowded world an issue that federal and state agencies frequently have to contend with is direct impacts from human visitation on habitat for a sensitive species. One of the key challenges in making such decisions is to balance the need for species protection with the need to provide the public with opportunities to see the species in question. Public support for a species and the actions necessary to ensure its survival are much more likely when the public actually has the opportunity to see the organism in its natural environment. Those interactions build empathy and fascination and a greater understanding of the threats that organisms face. Decisions to simply exclude people may provide some short-term protection but in the long-term people have to be part of the solution. 

In southern California where millions of people live within a one hour drive of several national forests, human use of those public lands is intense and conflicts with sensitive species are common. In 2002 the dwindling populations of the southern mountain yellow-legged frog (Rana muscosa) in the Transverse and Peninsular Ranges were listed as "endangered" under the federal Endangered Species Act (see In the News > ESA listing page for details). In 2005 the US Fish and Wildlife Service proposed several thousand acres of stream and riparian habitat as "critical habitat" for these R. muscosa populations. In response, in late-2005 the Angeles National Forest opted to close access to 1000 acre area along Little Rock Creek due to the presence of R. muscosa in this section of creek. This resulted in the closure of a popular climbing area, Williamson Rock, because it directly abuts Little Rock Creek. The closure also prevented access to a portion of the Pacific Crest Trail, forcing hikers to use a detour that required walking along a highway for some distance. 

The Angeles National Forest recently released a draft Environmental Assessment of the closure that proposes to keep the area closed for at least three more years while the response of the Little Rock Creek frog population to the 2009 Station fire is monitored.This potentially open-ended closure of the area has upset several user groups, in particular the climbing community (e.g., Friends of Williamson Rock). It is clear that user-created trails that access Williamson Rock and the proximity of some climbing routes to Little Rock Creek (some climbing routes actually start in the creek itself) have the potential to impact the frog population. However, many of these impacts would be relatively easy to mitigate. For example, the numerous user-created trails could be replaced by a single maintained trail and those climbing routes closest to the creek could be closed. In addition, climbers could be required to use "wag bags" for the disposal of all human waste. Discussions I recently had with a representative from the climbing community indicated that they are willing to work with the Angeles National Forest to implement these actions. It remains a big question whether the Forest will go along with this, however. 

The easiest action for agencies to take when confronted with conflicts  between human visitation and an endangered species is to simply restrict access. Although complete closures may sometimes be necessary, it is often possible to find creative solutions to conflicts that minimize impacts to sensitive species and in doing so help to build a constituency for conservation of the species. The Williamson Rock issue seems to have all the hallmarks of a situation where a suitable compromise is attainable. I hope the Angeles National Forest and Friends of Williamson Rock don't let this opportunity slip away. 

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A.B. 2376: Opening the Door to Restructuring the Department of Fish and Game

In late September California governor Arnold Schwarzenegger signed A.B. 2376 into law. This bill was supported by numerous fishing groups, including California Trout, Trout Unlimited, and The Sportfishing Conservancy, and was motivated by the recently-released Treanor Report that suggested changes to how the California Department of Fish and Game (DFG) and the California Fish and Game Commission (FGC) are structured (Treanor Report available here). A.B. 2376 requires that the Secretary of Natural Resources convene a committee to "develop and submit to the Governor and Legislature, a strategic vision for the Department of Fish and Game (DFG) and the Fish and Game Commission". Specifically related to the management of fish and game, it requires the following:

"....that the strategic vision address specified matters relating to fish and game management, including but not limited to: biodiversity management and ecosystem functions; permitting and regulatory functions; recreational and commercial harvest; scientific capacity; relations with the public, landowners, nonprofits and other land management agencies; reforms necessary to address challenges of the 21st Century; use of technology and data systems; clarification of the roles of DFG and FGC; and strategies for identifying other stable funding options to reduce DFG's dependence on the General Fund."

That is a pretty broad statement so who knows what will come of it. But the DFG and the FGC both certainly need to be updated to better accomplish their respective missions. One change that would be high on my list of priorities is for the DFG to increase its scientific capacity and to use science (instead of political expediency) to resolve resource-related disputes. An increased capacity to conduct critical resource-related scientific studies would go a long way toward allowing the DFG to anticipate resource problems. This proactive position would provide for far better decision-making than the current DFG model which seems to be to ignore growing issues for as long as possible and then deal with them in crisis mode when forced to by outside pressure. As I've said many times before, science will not provide all of the answers to our resource issues but it can provide a solid foundation upon which rational solutions can be developed.

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