This one slipped past me when it happened last June, but it’s well worth noting now.  Complicating assessments of the risks of bird deaths at wind farms is the fact that two-thirds of migrating bird species migrate mainly at night; Cornell’s Bioacoustics Research Program, which has already done groundbreaking work in elephant communication and underwater listening systems, has proposed that combining their autonomous recording devices with radar data could provide the missing information on exactly when and where concentrations of migrating birds may exist near proposed wind farms.

A compelling animation highlights the large-scale patterns: The color-coded radar map illustrates areas of precipitation over the coasts as well as vast movements of tens of millions of birds, bats and insects across the entire country. In the densest areas, the color-scales indicate movement of 2,000 birds per cubic kilometer. ”You’re talking about a massive movement of birds overnight,” said post-doctoral fellow Andrew Farnsworth.

Radar imagery of night-migrating birds, bats, and insects

Although radar data can show the magnitude, location, timing, speed and direction of migration patterns and provide information on key stopover sites, they do not identify types of birds or accurate flight altitudes, Farnsworth said. But combining radar data with data from flight call recordings and tracking tags on birds could allow researchers to identify many species in key areas. Bioacoustics program director Chris Clark added that recorders are cost effective, can be automated for many months at remote sites, provide data on many species simultaneously, increase the probability of tracking secretive and endangered species, and could allow regulatory agencies to develop computer models to assess risks to birds from wind turbines. He acknowledged, however, that using such acoustic technology could produce a massive “data crunch”; a single microphone over a three-to-four-month period can record 120 to 140 gigabytes of data, so data from several hundred microphones would be too much to process without advanced software. Also, researchers would need to better recognize the wide variety of flight calls and learn to integrate data from radar with those from acoustics and tracking tags, he added. More research is needed, Clark stressed, to determine at what altitudes species tend to fly and whether birds sense turbine blades and avoid them.  Read full account of the presentation in the Cornell Chronicle, with link to the radar map animation.

In the most promising development yet in using acoustics to deal with the spread of bark beetles in the American and Canadian west, researchers at Northern Arizona University have found that some beetles can be disrupted by playback of other beetle sounds. The tiny insects make squeaking noises as they tunnel through trees; the researchers have been manipulating the beetle sounds, which are above human hearing, and playing them back to the insects. The results drive them buggy: They attack each other, scamper in circles rather than straight lines and have tried to gnaw their way through Plexiglas covering a cross section of a tree in a lab in Flagstaff, Ariz.

A great article in The Missoulan included these tidbits from NAU researchers Richard Hofstetter and Reagan McGuire, Skye Stephens, an entomologist with the Colorado State Forest Service, and David Dunn, a sound artist who discovered and first recorded the beetle sounds:

“One of the questions is if we could effectively remove them from a particular tree or set of trees, where do they go, what happens to them?” Stephens said. “I’m very excited to see what happens next” with the research. Hofstetter and McGuire are eager to run tests on the ground to answer questions like that. Working with Dunn, they have applied for a patent on a device that pumps in noise to throw off the beetles’ destructive course. Hofstetter said the sounds are at a frequency that shouldn’t bother other species. The work has been a side project for the professor, who has struggled to scrape together funding for the research. McGuire is volunteering his time. ”We’re hoping it’s going to lead to a whole new field,” Hofstetter said.

David Dunn, who has traveled the world collecting sounds of nature for his compositions, first started recording the inner life of trees in 2004. He took the kind of small microphone used in greeting cards to record and play, fastened it to a recycled meat thermometer and inserted it into the tree. While concerned about the dying trees and what they signal about climate change, Dunn has become intrigued by the beetles, “an absolutely fascinating form of life. I fell in love with them,” Dunn said. “But then we’re watching them cannibalize each other. I always think, ‘How bad is this karma?’

“But if something really positive about forest health comes of it, perhaps it’s worth the price.”

Dunn’s CD, The Sound of Light in Trees, was released by EarthEar; 100% of all sales revenues are donated by Dunn and EarthEar to support the Acoustic Ecology Institute.  See more on the CD and beetle project on AEI’s website.

This came out in December, but I forgot to post about it then.  The National Park Service’s science magazine has published an entire issue devoted to the NPS’s soundscape studies and programs.

A couple strolls through Cathedral Grove on a quiet morning in winter when visitation is typically low. Signage at the entrance to this area reminds visitors that they are in a quiet zone. (NPS Photo/Lou Sian)

Articles include:

• Measuring and monitoring soundscapes in the national parks
• Integrating soundscapes into NPS planning
• Conserving the wild life therein–Protecting park fauna from anthropogenic noise
• Soundscapes monitoring and an overflight advisory group: Informing real-time management decisions at Denali
• Soundscape management at Grand Canyon National Park
• Generator noise along the US-Mexico border
• A program of research to support management of visitor-caused noise at Muir Woods National Monument

And, as they say, much, much more!  See the issue online here; from there, you can read every article in full. Note that the html views break each article into several separate pages, but you can also view in a “printer-ready” format that loads the entire article into a FlashPaper format, or you can view or download the full articles as pdfs.

Gordon Hempton, aka The Soundtracker, is featured on the Newsweek website this week.  Gordon shares his well-crafted gospel of quiet in both an interview and a very nice little video produced by Newsweek (there will be a pause after you click the play button, during which you will see a blank screen, rather than the commercial viewed at the Newsweek site):

I’ve just finished reading what must be the most exciting research paper I’ve seen this year, barely nudging out a similar paper addressing terrestrial noise impacts. A small group of researchers, with Chris Clark of Cornell as the lead author, took a giant step forward in addressing the impacts of ocean noise on the communication ranges of whales.  They came up with a clear and strikingly rigorous set of new metrics that will allow researchers and ocean planners to have a much more practical picture of how numerous noise sources combine to create cumulative impacts on acoustic habitat.  The new approach centers on the “Communication Space” of individual animals, as well as groups, and provides an intuitively obvious way to both imagine and assess the effects of ocean noise – measuring the area in which an animal can hear or be heard by others of its species.

My formal “lay summary” of this paper is reprinted in full below the fold, and I encourage anyone with a deep interest in ocean noise to read through that five-paragraph overview, or to download the paper yourself.  The key takeaway for those of you with a more casual interest in these issues is that in the test case that they used to illustrate their new approach, the researchers found that shipping noise has dramatically different impacts on different species, even though all three species they studied are low-frequency communicators.  In the area off Boston Harbor that they investigated, the critically endangered right whale is by far the most affected by shipping noise: on a day when two ships passed through the area (the average is often six), right whale Communication Space was reduced by an average of 84% over the course of the day, with several hours in which they could hear and be heard in an area less then 10% of that which would be expected without shipping nearby. Since right whales call back and forth to find each other as they form groups for feeding, this is truly worrying (though the key question of how a reduced communication range actually affects animals remains unanswered).  Fin whales and humpbacks were far less dramatically affected, with their Communication Spaces reduced by just 33% and 11% respectively.

These first examples focus on the effects of low-frequency shipping noise on low-frequency communication by large whales, but this approach can easily be used to address mid- or high-frequency noise sources (sonars, airguns) and higher frequency animal sounds such as those used for echolocation, opening a vast and exceedingly useful new doorway for biologists and ocean managers, as well as the general public, to appreciate the impacts of human sounds in the sea.   (click through for complete lay summary)

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An ongoing research project from the National Park Service Natural Sounds Program is about to publish a groundbreaking paper that outlines the many ways that even moderate increases in human background noise can create major impacts on animals.  The study proposes a new metric for use in bioacoustics research, the “effective listening area.”  This is the area over which animals can communicate with each other, or hear other animals’ calls or movements; as might be expected, animals focus especially on listening for sounds at the very edges of audibility, so that even a small increase in background noise (from a road, wind farm, or regular passing of airplanes) can drown out sounds that need to be heard.  The authors note analyses of transportation noise impacts often assert that a 3dB increase in noise – a barely perceptual change – has “negligible” effects, whereas in fact this increased noise reduces the listening area of animals by 30%. A 10dB increase in background noise (likely within a few hundred meters of a road or wind farm, or as a private plane passes nearby) reduces listening area by 90%.

In addition to introducing this important new metric, the paper provides a good overview of previous research that has addressed the impacts of moderate noise on various animals, including bats, antelope, squirrels, and birds.  The paper will be published next year, though an “in press” version is available for download.  A recent BBC article also covered this important new work.  A full detailed lay summary of this paper, as previously published on AEI’s science research page, appears below the fold: Read the rest of this entry »

A test run of one of the most promising new acoustic monitoring technologies is underway in Hawaiian waters: a six-foot long autonomous glider has been outfitted with a hydrophone, and has likely picked up foraging clicks of beaked whales.  University of Washington scientists did the glider’s engineering, while Oregon State researchers developed software to identify what is being heard.  ”We believe we have identified beaked whales,” says OSU’s David Mellinger. “It was pretty exciting. You work a couple of years on a project, hope it will succeed, but you don’t know until the equipment is wet.”  The current glider deployment, which began on October 27, is scheduled to end on November 17.  Here at AEI, we take special pride in this research, since Mellinger is one of our founding board members!

APL-UW's Jason Gobat and Jim Mercer and a ship crew member retrieve a Seaglider that had traveled a quarter of the way across the Pacific Ocean gathering oceanographic data

Read more about this study at Nature News, and see real-time records from the glider itself at the bottom of this page at UW (check this map to see all currently deployed gliders, though the others are not doing acoustics research).  You can also read more about UW’s glider research at their Applied Physics Lab website, and see this presentation on acoustic glider research from a different research team.

A five-week beaked whale Behavioral Response Study in the Mediterranean concluded in early September with a mixed bag of results: while researchers were unable to affix D-tags to any beaked or pilot whales, they were quite successful in using a new mobile Passive Acoustic Monitoring system which could be very useful in years to come. The study was largely aiming to track whales’ responses to various (low to moderate) levels of mid-frequency active sonar sounds using D-tags on the animals; previous Behavioral Response Studies using such “controlled exposures” have taken place on Navy instrumented ranges where the local populations are presumably familiar with sonar sounds, so they may respond differently than whales who have not heard these sounds before.  However, due to many periods of rough seas, as well as the inherent difficulties of finding, getting close to, and attaching tags to beaked whales (who dive for over an hour and come to the surface only briefly), no D-tags were deployed on whales, and no controlled exposures took place. However, a document prepared before the cruise, summarizing previous BRS results, is well worth reading: see especially page 8, which includes a detailed analysis of beaked whale responses to sonar and orca sounds: in both cases, the whales cut short foraging dives, but returned to the surface more slowly than normal, not more steeply as is sometimes assumed, and they clearly moved directly away from the sounds.

Beaked Whale (click for cruise blog home page)

However, researchers made the most of two other purposes of the cruise, both of which made use of a new passive acoustic monitoring technique.  The research took place on an extremely quiet research vessel, from which two hydrophone streamers were deployed, each of which had two hydrophones on it.  This gave listeners on the ship four separated sources from which to record and analyze sounds, so that most sounds could be quite well localized (direction and distance).  In addition, researchers deployed floating “sonobuoys” that provided more listening stations during times when groups of beaked whales were nearby.  This network of hydrophones provides much of the information that is provided by permanent bottom-mounted hydrophones on Navy ranges, and offers the potential to both find and monitor beaked whales in any location.  The hydrophone arrays were also collecting basic sound budget data, which will provide a better sense of the noises (both natural and man-made) that ocean creatures hear on a routine basis.  Click through for links to specific blog posts of interest, and a description of one day’s close encounter. Read the rest of this entry »

Ongoing research by NOAA’s Northwest Fisheries Science Center continues to look more deeply into the effects of boat noise on Puget Sound orcas.  The research team, led by Marla Holt, had previously found that orca calls increase in volume in step with background boat noise: for each decibel of added background noise, their calls also got a decibel louder.  In their latest round of research, the team is trying to determine whether the background noise is diminishing their foraging success due to masking (drowning out) some of the critical group communication, and whether calling louder makes the animals use more energy.

Image courtesy National Geographic

A 20% population decline among the Southern Resident orcas during the late 1990’s has been attributed to a combination of fewer salmon, toxins, and vessel noise. According to a recent article on National Geographic.com, Holt, who will present the team’s preliminary findings in October at the Biennial Conference on the Biology of Marine Mammal in Quebec, said that their research indicates killer whale communication is particularly important during hunting. What’s more, previous studies in birds had suggested that the animals consume more oxygen to raise their voices above ambient noise, making their metabolic rates spike and burning up stored energy, Holt said, adding that it’s possible the same phenomenon could be occurring with killer whales, although it’s too early to know for sure.

NOAA’s recovery efforts for the orcas include new regulations that will keep whale-watching vessels 200 yards from orcas, as well as efforts to reduce toxin pollution and to restore salmon runs.  Longtime orca researcher Ken Balcomb feels it all comes down to the decline in salmon: ”If you deny them the food, [there's] basically no point in worrying about other factors,” Balcomb said. He calls the whale-watching limits “feel-good thing,” adding that “my observations over 35 years [are] that [whales] don’t really get disturbed by anything, much less vessels.”  Holt acknowledges the limits of the new regs, saying that ”a lot of people would argue, Why focus on these vessel regulations? But it’s one thing we can do immediately.”  It appears to AEI that the question is not really whether the boat noise disturbs the orcas, but whether it may drown out parts of their foraging communication, making it more difficult for them to find and eat the few salmon that do remain available to them.  And, given their tenuous situation, if they are forced to use more energy to call during hunting, their overall health is likely to be at least somewhat affected.  Moreso, each time that a particular foraging attempt is aborted due to a noise intrusion, a larger bit of the daily energy budget has gone to waste.  Time will tell whether the new boat limits actually lower the received sound levels for foraging whales; if so, it’s a step in the right direction.

Fascinating discovery of the day: music written for monkeys, based on their vocalizations, finally triggers a notable response.  What follows is straight from the website of the composer, who also makes music for cats.  You can hear an NPR story on the monkey research here.

Many previous experiments on animal response to music composed for humans (hereinafter, “human music”) have been conducted, but none of these studies had demonstrated significant responses. Very recently a study of the effect of human music on cotton-topped tamarin monkeys was conducted at Harvard. The tamarins showed a slight preference for Mozart over German “techno” music, but preferred silence to either. This study was consistent with the findings of all previous studies: animals are largely indifferent to human music.

We performed tests at the University of Wisconsin on the same species of tamarins. As with all previous studies, the tamarins showed a lack of interest in the human music. By contrast, the effect on them of the species-specific music composed by David Teie was remarkably clear and convincing. They displayed a marked increase of activity in response to the music that was designed to excite them, while the “tamarin ballad” music induced a significant calming. This calming effect was measured against the baseline of silence; they moved and vocalized less and orientated more toward the audio speakers during and immediately following the playing of the tamarin ballad.

Following are quotes from a research paper about these experiments that will soon be submitted for publication. The psychologist Charles Snowdon, who conducted the testing and authored these statements, is a highly respected but extremely cautious and skeptical scientist not normally given to making sweeping statements: “Our predictions were supported. Music composed for tamarins had a much greater effect on the behavior of tamarins than music composed for humans. …tamarins displayed significant behavioral change only to the music that was specifically composed for them and were unaffected by human music.”

To the best of our knowledge, this marks the first time that an art form has been shown by scientific test and observation to engender the measurable appreciation of any species other than human. (Ed. note: true, little science has been done; yet there have been some compelling examples of animals themselves enjoying doing art: the painting gorillas and Thai Elephant Orchestra come quickly to mind.)

After a bit of a lull, I’ve spent much of the past couple days catching up on the folder full of research published in recent months, and summarizing key papers on the main Acoustic Ecology site.  Among the studies worthy of attention are:

• The first direct test of harbor porpoise sensitivity to seismic survey airguns confirms many observations from the field that this species is especially sensitive to noise; both temporary hearing loss and avoidance of sound occur at relatively low noise levels
• Orcas and dolphins seen to reduce foraging in the presence of boat noise
• Wind turbines don’t seem to replace most small wintering farm birds, but oil development noise can reduce forest bird abundance
• Right whales summer habitat is loud most of the time, suggesting a pressing need to identify their breeding grounds and assure they can hear each other there
• Two great overviews of fish hearing

See these and more at the AEI lay summaries of new research page.

Nice find of the day: A page on the Yosemite website describing the work they did over the past two summers to assess the soundscapes in the park.

http://www.nps.gov/yose/naturescience/soundscape.htm

And that’s not all!  There’s also a link to a half-hour MP3 file/podcast featuring the NPS Natural Sounds Program’s lead scientist, Kurt Fristrup, talking about his studies of the effect of noise on predator-prey relationships (a line of research that I tell people about more often than nearly any other), as well as noise effects on animal communications and human physiology. The audio feature also addresses the acoustic health of Yosemite as well as some interesting discoveries made possible through recordings made in the wilderness.  See the webpage here, and listen to the MP3 story here.

One of the more exciting new technologies to come of age in the past couple years is ocean “gliders” that can cruise the seas, silently or nearly so, while collecting data ranging from temperature and salinity to sounds. The gliders are small (roughly 6 feet long), and surface periodically to send data to satellite communication systems. Some gliders are battery powered and can cruise for about a month, while the leading edge approach is to use a temperature-sensitive ballast that allows the glider to travel for up to five years at sea.  As a tool for working with ocean noise issues, gliders hold great promise for use in monitoring the seas before sonar trials, as well as for regional acoustic mapping/monitoring.  In late 2007, researchers at Defense Research and Development Canada used a glider to listen in on beaked whale calls; recording and analysis take place while the glider is below the surface; by the time it surfaces to send its data to researchers on shore, “it already thinks it knows whether it has a beaked whale or a sperm whale,” according to lead researcher Jim Theriault.  The US Navy has a few training ranges where bottom-mounted hydrophones make it much easier to monitor for beaked and other whales before and during sonar exercises; gliders could bring this advanced capability to sonar training anywhere at sea.

WHOI glider in the water

This spring, the US Navy placed orders for $6 million worth of Littoral Battlespace Sensing-Gliders (LBS-G), with options for up to $50 million more over the next four years.  It appears that, at least for now, the Navy is planning to use the gliders as part of their near-shore (littoral) defense system, rather than as adjuncts to monitor for whales near sonar exercises.   Early this year, the NATO Undersea Research Group (NRUG) ordered 4 to 7 gliders, though it’s unclear whether they will be outfitted with hydrophones.  At Woods Hole, Mark Baumgartner’s research group has been using a fleet of 20 gliders (which were initially developed at Woods Hole, before being commercialized by a WHOI scientist) to listen in on baleen whales as they study whale distribution and habitat in the Gulf of Maine; however, before long-term deployment and research can begin, the team is developing instruments and software to allow for near real-time assessment and classification of the sounds.  Once that’s up to speed, larger scale monitoring can begin.  Non-acoustic gliders are in use worldwide by Rutgers researchers, where the Coastal Ocean Observation Lab (COOL) has been using them since 2003.

Gliders hold great promise as a benign yet active platform for ocean observing, especially in acoustics.  Any boat-based monitoring brings its own noise along for the ride, while bottom-mounted hydrophones need more complex communication systems (generally cables).  Gliders are effectively silent, and move so slowly that even in the case of a fluke collision with a sea creature, no harm will come to either party.  Keep an eye on this exciting new technology!

This one sat around for a while waiting for me to write about it, but it’s pretty timeless, so here goes!  One of the leaders in fish bioacoustics, Rodney Rountree, wrote a great overview piece in the Nov/Dec issue of Marine Technology Review on the groundbreaking work being done in fish biology using Passive Acoustic recording systems.  The article does a wonderful job of introducing the various approaches being taken to recording freshwater and oceanic fish.  The most exciting aspect of this work is that until quite recently, very few biologists even CONSIDERED fish as vocal or acoustic creatures (the emphasis was on chemical/smell and mechanical/tactile sensitivity).  As Rountree notes, “currently most biological sounds recorded in marine and aquatic habitats are unknown due to the lack of study and a lack of comprehensive sound catalogues.”  It’s agua incognita!  

To enter this fascinating new acoustic world, Rountree has compiled three distinct yet complementary overviews:

• The article in MTR is on Page 40 of this pdf version of the issue. 
• You can download his 42-page “e-book” nominally written for children, but in fact a wonderful layperson overview of the history and current discoveries in fish acoustics; it’s full of links to websites. 
• And, his academic website FishEcology.org has a page that is full of fish sounds, including a slew of unidentified sounds. 

The early 2009 issue of Conservation magazine, the popular press publication of the Society for Conservation Biology, has a great overview piece on the effects of noise on animals. It focuses on changes in animal behavior and song that have been observed over the course of the past decade, drawing on studies from several different researchers. Much will be familiar to AEI regulars, but it remains highly recommended for sharing with others and for the concise overview it provides.

See the article at http://www.conservationmagazine.org/articles/v8n2/not-so-silent-spring/

Here at AEI, one of the fun tasks on my plate is writing lay summaries of new scientific research.  Usually.  Early in 2008, a dense volume of the journal Aquatic Mammals was published, which featured the results of a multi-year effort by an all-star team of American ocean noise researchers, who were attempting to distill all the current research on ocean noise, and to recommend Exposure Criteria for marine mammals.  Suffice to say, I read it several times, highlighting madly, but kept putting it aside, reticent to attempt a coherent narrative summary.  

Well, I finally followed through, and what follows (below the fold) is a pretty decent summation of what they came up with.  The headline news is twofold: in addressing noise that may cause physical injury (defined as permanent hearing loss), the authors present a dizzying array of extrapolations and assumptions (largely precautionary but sometimes pure leaps of faith) in order to try to assess the impact of extremely loud sound on marine mammals, given that there is very very little direct data to work with.  They conclude that safety limits could be modestly increased without deafening more whales.  On the behavioral side of the ledger, things are not that much clearer, but much more fascinating.  A series of charts that compile results from all known behavioral response observations highlight the wide range of responses that a given level of sound may cause, but also provide some solid evidence that many marine mammals show fairly dramatic behavioral change when encountering fairly modest sound levels, far below those that current regulations consider necessary to monitor.  With that, if you want to know more, I invite you to click on through….

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