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Kroll A.J.,Weyerhaeuser Company | Lacki M.J.,University of Kentucky | Arnett E.B.,Bat Conservation International
Western Journal of Applied Forestry | Year: 2012

Snags provide habitat for numerous vertebrates and invertebrates. We review how current regulatory guidelines and forest management practices influence snag populations on intensively managed landscapes in the Pacific Northwest. We identify ecological relationships that require investigation to assess alternative practices that optimize ecological and economic goals. Functional and numerical relationships among snag type, abundance, and distribution and demographic responses of both vertebrates and invertebrates are poorly understood. Relatively little is known about temporal and spatial distributions of snags required to maintain viable populations of cavity-dependent taxa or how landscape-scale features (e.g., proximity and amount of mature and late-successional forest) interact with snag types and distributions at the stand level to influence wildlife responses. Regulations for snag retention have been developed and implemented with a substantial degree of uncertainty about their ecological effectiveness. Current regulations, designed to protect forest workers from injury, typically limit retention of snags of large size and advanced decay classes that are often the most limited snag types on intensively managed landscapes. We describe current findings and future research needs that can be used to evaluate operational and ecological effectiveness of current regulations that influence snag management. We identify questions of interest and frame these within the appropriate ecological context of intensively managed landscapes. Copyright © 2012 by the Society of American Foresters.


Hane M.E.,Weyerhaeuser Company | Kroll A.J.,Weyerhaeuser Company | Johnson J.R.,Weyerhaeuser Company | Rochelle M.,Weyerhaeuser Company | Arnett E.B.,Bat Conservation International
Forest Ecology and Management | Year: 2012

Managers of landscapes dedicated to commodity production require information about how alternative practices can promote retention of native biological diversity. Retaining or creating structural features (e.g., snags or downed logs) needed to fulfill life history requirements may benefit populations and communities. However, demographic responses of species to alternative practices have received little research attention. We tested nest survival of cavity-dependent birds in response to experimental structural enrichment by creating snags on 28 plots, Oregon, USA, 2008-2010. Each plot represented one of six combinations of created snag density (0.5, 1, and 2. snags/ha) and spatial dispersion (clumps of 5-7 snags or dispersed individual snags). We monitored 506 nests built by 10 species; three species nested in sufficient numbers for analysis. Chestnut-backed chickadee Poecile rufescens nest success was highest in the medium density clumped created snag treatment (average proportion of successful nests = 0.76; 95% CI = 0.61-0.87) and lowest in the low density clumped treatment (average proportion of successful nests = 0.39; 95% CI = 0.20-0.62). We did not find a response of either house wren Troglodytes aedon or northern flicker Colaptes auratus nest success to the experimental treatments. Period survival rates were 0.57 (95% CL: 0.39-0.72) for CBCH; 0.71 (95% CL: 0.51-0.84) for HOWR; and 0.59 (95% CL: 0.34-0.77) for NOFL. Our study suggests that creating snags in commercial harvest units is an effective practice for increasing structural complexity and supporting nesting communities of cavity-dependent birds. While leaving either clumped or dispersed created snags at a density of ∼1. ha should support nest survival rates that are similar to those reported from unmanaged forests, we emphasize that this type of structural enrichment is not a panacea for species that require very large snags or snags that occur under complex forest canopies. Retention of existing structural features in reserve areas may be an appropriate practice for conserving species with nesting requirements that differ from those we evaluated in our study. © 2012 Elsevier B.V.


Kroll A.J.,Weyerhaeuser Company | Duke S.D.,Weyerhaeuser Company | Hane M.E.,Weyerhaeuser Company | Johnson J.R.,Weyerhaeuser Company | And 3 more authors.
Biological Conservation | Year: 2012

Landscape composition may have a substantial influence on species use of habitat at local scales and effectiveness of structural enrichment practices (e.g., augmenting existing amounts of snags or downed logs). If sufficient mature (i.e., cavity containing) habitat exists at the landscape scale, cavity nester demand for nest sites could be reduced due to the surplus of existing sites (habitat surplus hypothesis). Alternatively, if mature forest acts as source habitat for cavity nesters, increased amounts of mature forest in the landscape will inflate the demand for snags in clearcuts (habitat source hypothesis). In Oregon, USA, we evaluated cavity nesting bird colonization of experimentally created snags distributed across a gradient in amount of mature forest at the landscape scale. We sampled 28 plots, each of which represented one of six combinations of created snag density (~0.5, 1, and 2. snags/ha) and spatial dispersion (clumps of 5-7 snags or dispersed individual snags). We tested whether early successional and mature forest species groups responded differently to plot-level treatments and if the percentage of mature forest (>40. years old) within a 1000. m radius surrounding each experimental plot influenced this response. Mature forest species more readily colonized created snags as the percentage of mature forest declined in the landscape, supporting the habitat surplus hypothesis. Estimated use by mature forest species increased from 7% to 17% as percent mature forest in the landscape declined from 58% to 13% (estimated for average levels of created snag density, 0.4. snags/ha, and a spatial distribution of 45. m). Colonization of snags by early seral species also increased with decreasing mature forest (from 3% to 9%), which may support the habitat source hypothesis. Our study suggests that creating snags in commercial harvest units is an effective practice for increasing structural complexity and maintaining nesting communities of cavity-dependent birds. At the local level, created snags should be spaced as widely as possible within individual harvest units. However, our results indicate that effectiveness of snag creation will be highest in the most intensively managed landscapes where the amount of structurally diverse habitat is limited. © 2012 Elsevier Ltd.


A hiker who noticed a little brown bat dying on a trail near the slopes of the Cascade Mountains in western Washington did what he could to save it. He took it to an animal health center, but within two days it was gone. The death in mid-March seemed unremarkable until a veterinarian who examined the animal made a discovery that set off alarms heard all the way to Washington, D.C. The bat showed advanced signs of white-nose syndrome, a mass killer that emerged in New York about 10 years ago and slowly migrated as far west as Nebraska, leaving nearly 7 million bats dead in its wake. Its sudden, thousand-mile leap to the Pacific Northwest is a grave concern to every biologist who studies the winged mammals. The find potentially opens up a second epicenter for the fungus. Even now, scientists don’t know precisely where it came from, much less where it’s going. All they know is that it kills virtually every bat it touches. [The toll from White Nose syndrome: Nearly 7 million bats] “I think this is really bad,” said Katie Gillies, director of the Imperiled Species Program at Bat Conservation International in Texas. “I really do think this is a big leap. Now we’re going to see it radiate from that new point. It’s like having breast cancer and finding that it’s metastasized.” The U.S. Fish and Wildlife Service, which has tracked white-nose syndrome since 2006, also expressed alarm, but with far more reserve. The next steps will involve genetic testing of the dead bat, along with analysis of the disease that killed it, and then a state-led sweep of the trails and mountain crevices visited by bats near the hiker’s discovery. “We are extremely concerned about the confirmation,” Fish and Wildlife Service Director Dan Ashe said in a statement. “Bats are a crucial part of our ecology and provide essential pest control for our farmers, foresters and city residents, so it is important that we stay focused on stopping the spread of this fungus.” Wildlife biologists want to be sure of where this disease strain originated. Among the questions they’re seeking to answer: Did a traveler track it from Europe or Asia all the way to the west coast? Or did some cave explorer get the fungus on his or her gear in the east and bring it west? They want at least a clue to how long the fungus has lived out west. Considering the haggard condition of the dead bat, including its ravaged wings, a tell-tale sign of white nose, it’s been there for a while. “Every single avenue we look at seems far fetched,” said Greg Falxa, a wildlife biologist for the Washington Department of Fish and Wildlife. “This bat had the deterioration already, which suggests the fungus didn’t just get here this year. Who knows how it got here? Everything is speculation right now. We’re starting surveillance in that area.” That immediate surveillance is yet another sign of the degree of concern. White-nose syndrome has nearly pushed brown bats in Pennsylvania and New York to extinction. It’s now established in at least 25 states and several Canadian provinces. Their loss has substantial implications for humans. Bats eat insects by the metric ton every night, with a pregnant female capable of devouring nearly a hundred moths and other pests. In a single summer, a colony of 150 brown bats can eat enough adult cucumber beetles to prevent the laying of eggs that result in 33 million rootworm larvae, according to a study cited by Bat Conservation International. [A cry in the dark but no answer: This is how a fungus kills bats] Without bats, insects would be free to ravage farm crops and trees, among other things. Their value to U.S. farmers has been estimated at $3 billion a year. In addition to little brown bats, long-eared bats, big brown bats, Indiana bats and grey bats have been impacted. Falxa said the latest discovery led to a frenzy of conferences between his agency, Fish and Wildlife and the U.S. Geological Survey. They have one hope: Bats in the west don’t congregate in caves and mine shafts by the tens of thousands the way they do in the east, so maybe, Falxa said, the fungus won’t spread as fast. But Gillies, who was once a biologist in Nevada, called that a false hope. “We’ve got 15 western species that have the potential to be infected,” she said. “Containment is not going to be possible.” Gillies offered a prediction, saying that as the fungus wipes out the most susceptible bats, others will flourish in their absence because of less competition and a larger abundance of food. Still, even if they develop an immunity to the fungus as their counterparts did in Asia and Europe, “bats are really long lived… and slow to reproduce,” she said. “They’re very slow to rebound. We won’t see it in our lifetime.” Bats are hit hard by a deadly one-two punch: White nose and wind mills Ten reasons why bats are a lot cooler than you think For more, you can sign up for our weekly newsletter here, and follow us on Twitter here.


Cryan P.M.,U.S. Geological Survey | Gorresen P.M.,University of Hawaii at Hilo | Hein C.D.,Bat Conservation International | Schirmacher M.R.,Bat Conservation International | And 9 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2014

Wind turbines are causing unprecedented numbers of bat fatalities. Many fatalities involve tree-roosting bats, but reasons for this higher susceptibility remain unknown. To better understand behaviors associated with risk, we monitored bats at three experimentally manipulated wind turbines in Indiana, United States, from July 29 to October 1, 2012, using thermal cameras and other methods. We observed bats on 993 occasions and saw many behaviors, including close approaches, flight loops and dives, hovering, and chases. Most bats altered course toward turbines during observation. Based on these new observations, we tested the hypotheses that wind speed and blade rotation speed influenced the way that bats interacted with turbines.We found that bats were detected more frequently at lowerwind speeds and typically approached turbines on the leeward (downwind) side. The proportion of leeward approaches increased with wind speed when blades were prevented from turning, yet decreased when blades could turn. Bats were observed more frequently at turbines on moonlit nights. Taken together, these observations suggest that bats may orient toward turbines by sensing air currents and using vision, and that air turbulence caused by fast-moving blades creates conditions that are less attractive to bats passing in close proximity. Tree bats may respond to streams of air flowing downwind from trees at night while searching for roosts, conspecifics, and nocturnal insect prey that could accumulate in such flows. Fatalities of tree bats at turbines may be the consequence of behaviors that evolved to provide selective advantages when elicited by tall trees, but are now maladaptive when elicited by wind turbines. © 2014, National Academy of Sciences. All rights reserved.

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