Category Archives: Bioacoustic revelry

Sounds from the edge of Boreas’ kingdom

A raven flies to its roost at dusk, wingbeats audible between the calls. Just before this flight, the bird was amusing itself with half a dozen others of its kind by harassing a sluggard-winged eagle. The ravens wove and swooped; the eagle flopped its great wings, finally passing out of sight on the horizon.

I think the squealing call at the end is a younger raven, greeting its homeward-bound parent.

Spectrogram of the same sound. Time moves left to right, pitch increases along the vertical.

Spectrogram. Time moves left to right, pitch increases along the vertical. “Stacked” lines are harmonics.

Night came and with it a frost.

Fir at nightI lingered and was rewarded by the sounds of Northern Saw-whet Owls. These tiny owls are common in dense forests of Canada and the Western US, especially forests with rotten trees to supply nesting holes. In the winter, some birds move south, so Saw-whets can be found all the way to Florida in the right season. The bird gets its name from the supposed resemblance between its repeated whistled call and the action of whetting a saw. The analogy is stretched, unless your saw comes with a flute.

The owls were a distance away, so the following recording has some lower and higher sounds filtered out to make the call come through more clearly.

SawWhetOwlSpectro

One tiny part of the rainforest song

Twilight is brief in the tropics. The sun drops with none of the lingering obliqueness of its behavior in temperate and polar areas. My visit to Ecuador placed me almost directly on the equator, so after I watched the sunset from a tree canopy, I hustled to get back to the camp. The trail turns completely dark within a few minutes of sunset.

As I jogged along, a song stopped me in my tracks: a pure tone from the rainforest, then another seemingly in answer, then one more from far across the stream. I’d never heard such a sound. The purity of a thrush, the loudness of a goose. Close.

I captured a few seconds (turn up your volume!):

Here are the spectrograms, with time moving horizontally and pitch (frequency) increasing vertically. The whistles are the low dark marks; all the rest of the sounds are insects and distant birds:

TinSpec2These are the calls of tinamous, ground-dwelling birds found only in the New World tropics (first, the variegated tinamou, then the great tinamou, I believe, but neotropical bioacousticians please feel free to correct me). When I studied their biology in zoology classes I never thought I’d be in their presence. Here they were, though, singing within a few meters of me in the Ecuadorian Amazon. Stunning.

Tinamous have strange habits, at least by the standards of other birds. The males defend nests into which multiple females lay astonishingly glassy eggs. The male incubates the eggs, broods the hatchlings, and guards the young. The females wander from male to male laying more eggs. Tinamous seldom fly, and then rather poorly, preferring to strut in the undergrowth of their forested territories.

Recent molecular research strongly suggests that tinamous are the relatives of the extinct New Zealand moas. This grouping is clustered within the larger “family” of ostriches, emus, rheas, kiwis, and cassowaries. So tinamous are a zoological echo of the ancient southern continent of Gondwanaland, a continent now fragmented into many parts, each carrying biological stowaways. The tinamou song is the closest we’ll come to hearing a moa.

In their biogeographic wanderings, the tinamous seem to have picked up the quena from the mountains to the west, slicing through the acoustic tumult of the Amazon with their melodies. Or perhaps the quena, a recent arrival by zoological standards, is inspired by the Andean tinamous?

Tinamous sing at dawn and dusk, so their music rings out only briefly, bracketing  Amazonian nights and days.

 

 

 

 

White pine wood for breakfast

You can hear them from twelve feet away. Rhythmic grating sounds from within a dead white pine tree in our neighbor’s yard. Sarah heard them first on her early morning walk. We returned later in the day, but the munchers had fallen silent. It seems that their appetite is keenest at dawn.

Here are the sounds, with a labeled spectrogram of the same sound. I suspect that the crunching sounds are coming from large Cerambycid larvae (long-horned beetles). The hairy woodpecker that was diligently extracting them from under the bark would know for sure. Beetle larvae that live under bark can thrive on seemingly indigestible wood using a combination of detoxifying enzymes produced by their own guts and through use of cellulose-digesting enzymes that the insects derive from the fungi that live inside the wood. This is a bit like digesting moldy cornflakes by harnessing the power of the mold. A clever strategy, but one that I’ll leave to the beetles.

Spectrogram (time moves left to right; frequency (pitch) is on the vertical axis):

Chew

Listen: underwater crackly, groany kōans

Drop a hydrophone into shallow salt water at latitudes less than 40° and you’re likely to hear a crackling sound, sometimes so loud that it drowns out almost all other underwater sounds. This din is created by snapping shrimp, tiny crustaceans that click one of their front claws so fast that the motion creates a bubble of air, a cavitation in the water. The rapid opening and closing of the bubble generates sounds as loud as 200 dB (as loud or louder than dolphins and whales) and very briefly heats the bubble to a temperature just shy of that on the surface of the sun. Understandably, nearby prey are stunned, as was I when I read these figures. The shrimp also use their loud, hot snaps to wrangle over territories and to attract mates.

Here are the sounds of these creatures recorded from the dock at St Catherine’s Island (if you’re an email subscriber or viewing on a phone, you might need to click on the header link to go to the website to get sounds…):

 

In some tropical sponge-dwelling snapping shrimp “a sentinel shrimp reacts to danger by recruiting other colony members to snap in concert for several to tens of seconds” (Tóth and Duffy 2005). So these shrimp are somewhat like crows, honeybees, and other social creatures: networking information through their societies.

Another sound from the dock, heard amid the shrimp (I filtered out many of the high frequencies to make the sound a little easier to hear):

 

This is the territorial call and the mating cry of a toadfish. These ogre-like creatures sit under rocks or in crevices the bottom of the seafloor, waiting to ambush smaller fish and other morsels. The Billy Goat Gruff of the seas. Their mouths are liked toothed baseball mitts.

Despite its unappealing visage, the toadfish has much to recommend it to the curious naturalist. The call is produced by vibratory muscles attached to the swim-bladder (bagpipes?). These muscles are the fastest known among all vertebrates. Once mating is done, the male toadfish defends the eggs, then guards the hatchlings until they find their own bridge to hide under.

NASA once sent toadfish into space. According to Wikipedia, they found that toadfish inner ear bones developed in the same way in orbit as back here on planet Earth. Good to know. This study also answers the kōan,

Can a toadfish in space orbit be said to be under his rock?

But poses a new one,

If a toadfish vibrates his swim bladder in the vacuum of space, is he singing? And, for extra kōa-credit, who might answer his airless call?

For now, toadfish are hiding under their rocks with even greater diligence, fearing capture for space experiments, waiting for Homo sapiens to pass on by. Here is the sound of our departure from the dock, heard from the toadfish’s watery home:

 

Many thanks to Dr John Schacke from UGA and the Georgia Dolphin Ecology Program who helped me to understand what I was hearing.

Washed up

The students in the Sewanee Island Ecology Program have repeated the studies that I began last year of “trash” on the beaches of St Catherine’s Island, GA. We search standardized transect lines in the wrack on the upper beach.

If our samples are representative of the whole beach, and assuming a 20 meter wide wrack line, a 10 km stretch of beach would have just shy of half a million individual pieces of anthropogenic debris. Foam pieces are the most common (80% of pieces), followed by other plastics. Half of all debris pieces were 2cm wide or smaller. These data only include pieces of debris that are visible on the surface. Much more is likely buried deeper. We did not examine microscopic fragments.

Here are some photos of some of the items we found.

stcatsbeachdebris0

Brut. Advertized on their websites as the “Essence of Man.” Indeed. This one washed up from …somewhere… as we were walking our transects.

stcatsbeachdebris

Epibionts on plastic bottle. Darwin would be proud. It’s all about barnacles.

stcatsbeachdebris2

Still life with pill bottle.

stcatsbeachdebris3

Just what the ocean needs, a little more engine oil. Probably drilled from under the ocean. Sustainability is all about closing the circle…

I also made some sound recordings along the beach. The first is made with a hydrophone, a microphone that picks up sounds below the surface of the water. I suspended it in some gentle surf. The second recording is the same surf, but recorded with a regular microphone, in the air, at the top of the beach.

Hear this and tremble, carpenters, barn-dwellers, and other lovers of naked wood

 

The sound of a female carpenter bee (Xylocopa virginica, the “Virginia wood-cutter”) chewing wood fibers at the end of her tunnel inside a piece of exposed wood in a barn. She’s chewing away with her sharp mandibles, making a tubular nest for her eggs. She’ll provision these with nectar and pollen, giving the young a well-protected place to start life. The mother bees overwinter in their tunnels and their offspring often bore new holes close to the natal hole. So a cluster of bees on a single board or in one part of a barn is often a family group. Here’s a photo from 2012 of a modest-sized tunnel. These borings can get much bigger, hollowing entire pieces of wood.

Surely the invention of the saw opened huge new opportunities for this species of wood chewer. Before humans came along, the bees had to wait for branches to crack open or for wood to expose itself in other ways. Carpenter bees must regard humans as evidence of intelligent design: we’re a species whose only purpose is to erect grand temples of dimensional lumber for carpenter bees. Amen, sisters. Teleology is a fine thing.

What a beech twig hears…

…when a gust of wind passes over its leaves. These are the vibrations that tremble through the wood. Inaudible to our ears, but the tree’s cells are shaken (not stirred) and any insect in the twig could detect the vibrations through its feet.

 

I recorded this today using a tiny accelerometer on the twig’s surface. The leaves have been out for a week or two, so they are still very delicate.

“But their comprehensive silence stays the same”? Not so, Professor Nemerov, not so.

Toads, Saint Patrick, and biogeography

Warm the soil, add an inch or two of rain. The result: toads. Defrosted and ready to grasp springtime’s possibilities.

toads_amplexusAs I write, I hear one trilling in the pond outside. Hopefully the next weeks will bring dozens more. Toad song after a long, long winter is melodious glory.

Thanks to St Patrick (on whose feast day I’m posting this), the Irish don’t get to delight in the sounds of Bufo bufo, the common European toad. Apparently Patrick kicked them out along with the snakes. It is a herpeto-theological mystery why the saint chose not to preemptively bar more pestiferous species — biting flies, fungal blights, or the English — instead of the humble toad. His work was incomplete, though: the rarer natterjack toad has a toe-hold in a few parts of Ireland.

These tales of missing species from islands point at an important area of study in biology, namely the curious fauna and flora of isolated land masses. The technical term is “disharmonious.” Islands have communities that contain some, but not all, of the species of nearby continents (the islands are therefore out of “harmony”). The more distant the island, the more peculiar the biological community, all a result of the unlikelihood of colonization. Ireland is missing just a few European species. In contrast, the Galapagos islands sit far out to sea and are missing most of the species of mainland South America. Indeed, so few colonists have made it to these outposts that in situ evolution has provided much of the local diversity. The same is true of the Hawaiian islands and other oceanic isolates.

This disharmony is hard to explain from a creationist perspective, so it is no accident that islands feature prominently in the thinking and writing of the originators of the theory of natural biological evolution, Darwin and Wallace. To them, the idea that the distribution of animals and plants is explained by the particularities of historical accident seemed a more fruitful hypothesis than de novo creation.

Now of course, we’re erasing all this isolation with our planes and ships. Our mobility is undoing St Patrick’s work, homogenizing the world, sometimes with regrettable consequences: here is a list of the non-native species currently threatening Ireland’s biodiversity. More saints needed?

Graupel into beech

Yesterday, on the leading edge of the snow storm, rain turned icy, pelting the woods with interesting nouns-that-should-be-verbs: rime and graupel. This bombardment made for delicious sounds, and not just on the human tongue.

Here is the percussive beat of this snowy ice falling into the marcescent leaves of a young beech (heard best with headphones):

In .wav format:

In case your browser doesn’t like .wav, the same recording, in .mp3 format:

Next morning, Junebug and I had the pleasure of making the first tracks on the snowy trails, listening to the whomp and whisper of the woods.

2014-02-13 ash shakerag snow 019

An entomological Milesian tale

Milesia virginiensisMilesia virginiensis2The common name for this wasp-mimicking fly is “news bee” or, more optimistically, “good news bee.” The moniker was given to the insect for its habit of zipping through the air toward a human then holding steady, imparting the news in a loud buzz. Once the news has been sung, the fly flings itself away to find another willing ear.

This habit might also account for the generic name of the species, Milesia (this one is Milesia virginiensis, I believe). Milesian tales are lurid, captivating short fables, named for Aristides of Miletus, “a writer of shameless and amusing tales with some salacious content and unexpected plot twists” (or so says that rock of classical knowledge, Wikipedia). A fly’s version of a Milesian tale would be fun to hear, but regrettably I could not translate the buzz that I heard in Shakerag Hollow and so missed this Dipteran’s narrative complications and witty innuendo. Maybe you can do better: my recording of the insect follows. The fly was perched on a leaf, washing its forelegs. Suddenly it launched itself and flew to me to give The News. Once done, the fly darted away to gossip at a fallen tree, then shot out of earshot.

(Web browsers differ in how they handle sound files, so I have uploaded two files: the first is mp3 and the second is m4a. You’ll either see a “play” button, an option to download, or both. The background sounds are cicadas and a Carolina wren.)