Month: July 2020

Don’t Write Off the Bat

It was a perfect evening for a spin in the Batmobile with a team of three amateur chiroptologists. The air was warm and still when the sun went down.

After leaving the carpark, we were overtaken by every vehicle along the Colonial Parkway as we crawled at 15 mph, hugging the kerb. Fortunately, the traffic was light. It was too dark to see if the faces passing us were puzzled by the tall aerial sticking out of our sunroof or if they guessed what we were up to from the sticker on our trunk illuminated in their headlights: Bat Monitoring – Pass Safely.

Although I rarely hear bats nowadays, I love to watch their silhouettes against the last glow of a darkening sky. Their acrobatic flights look sheer joy, although I know they are to satisfy voracious appetites, twisting and turning to skim the air of mosquitoes, moths and lumbering beetles.  After years of wondering what species lived here, I now had an opportunity to find out.

The passenger sitting beside the driver held the aerial with one hand and used the other to control the tracker pad of a laptop perched in front. I watched over her shoulder as she loaded the SonoBat software.

SonoBat
All set in the Batmobile

We hadn’t gone far along the tree-lined parkway when the computer chirped. It was our first hit. A chirogram on the screen (like a sonogram) showed regular pulses as a bat called for echolocation to detect prey and avoid obstacles. A machine-learning algorithm identified the species, saved data to a spreadsheet and could mark ambiguous results, if necessary. The passenger in the seat beside me backed up results by writing on a notepad. We had detected a Red bat, named for its red fur. It was impossible to see it or any others through impenetrable night.

This was my first time for a bat positively identified while flying free in the wild. Soon, there was another chirping, then another, often in a different tone and frequency. After two hours on the road we gathered 125 recordings, mostly ascertained. The total number of individuals was, however, unknown, and we probably had duplicates because bats of a given species have the same voice. But we were more confident that seven species flew close enough to detect that night, including the Big-eared, Big brown, and Silver bat. I never knew we had so many.

chirogram fromSonoBat
Chirogram of Red bat

The software program identified calls by referencing a library of thousands of recordings of species from across the continent.  We mostly detected Red bats, a common and widespread species. The Seminole bat has a similar chirogram, but being near the northern limit of its range it was unlikely to be mistaken for the closely related species.

When I joined the survey one night last year, bats were getting more attention from conservationists and there was growing public interest in their dwindling populations from loss of habitat to human development, Insectageddon threatening their food supply, and the toll from white-nose syndrome.  They haven’t lost friends who always cared about them. But people who were indifferent before or harbored superstitions can find a better excuse for fearing them than the old myth that bats get caught in young girls’ hair.

Evidence is growing that the COVID-19 virus originated in bats before it infected humans, perhaps via an intermediate host. The species and country of origin are still unclear. Bats harbor coronaviruses to which they evolved enviable tolerance from long association and robust immunity. They have orthologs of our ACE-2 protein, a molecule with a physiologic role and widely distributed on our cells that offers the virus a gateway for infecting us by binding its spike protein.

To persecute bats as suspects of this or other zoonoses (certainly they can carry the rabies virus, like any other mammal) is no more justified than putting people in jail for spreading disease before they understood the menace or knew they were infected. Solutions to our problem lie not with the animal but in our connected world and with global travel.

Bats flying at night
Thanks to Ruth Rios on Unsplash

Bats are fascinating creatures in the web of life. They cling to familiar habitats and if left alone they help us as insect-eaters and providers of pollination services.

When contact distancing is revoked after the pandemic, I hope to board the Batmobile again to watch pulses on the glowing screen that spark imagination about the peregrinations of bats outside in the night.

Next Post: On Human Population

Virginia is for Oyster Lovers

“Why then the world’s mine oyster, which I with sword will open.” Thus, Shakespeare gave us a new idiom in the Merry Wives of Windsor repeated ever since, and Oscar Wilde wielded it with customary wit: “The world was my oyster, but I took the wrong fork.”

It means a person expects to avoid adversity and find opportunity, like the discovery of a precious pearl. But if you asked an oyster it wouldn’t sound optimistic. Our excessive love kills them, and few cared about the relentless harvest until recently. In the poem recited by Tweedledee and Tweedledum, Alice felt sorry for oysters as the Walrus and Carpenter gobbled them on the beach.

Had we been aboard the shallop steered by the first English explorers of the Chesapeake Bay in Shakespeare’s day we would have been gobsmacked by an abundance of oysters, some as large as dinner plates and forming reefs grown close to the surface.  In 1701, a foreign visitor wrote in astonishment: “whole banks … ships must avoid them … four times as large (as English oysters) … I often cut them in two to put them in my mouth.”

The Bay was drastically impoverished by dredging its bed barren in the 19th century Oyster Rush.  The local economy collapsed and watermen switched to crabbing to make a living. The crash drastically impacted other fauna and flora since the remaining 2% of original numbers now took a year to filter the entire Bay which used to be achieved in a week. It is a classic example of the folly of free-for-all harvesting of a seemingly inexhaustible natural resource. Oyster beds are now making a slow recovery against a tide of agricultural effluent and disease, but helped by volunteers for the Chesapeake Bay Foundation and less harvesting pressure as oysters are cultured commercially.

If they are on your menu today, imagine the same shells on your plate again. The suggestion is ridiculous, but the point is that some restaurants in our region recycle shells for building wild oyster beds and embedding in artificial reefs. At one time, they were used as lime for mortar and roads, but when that became redundant they were dumped in landfills, so the recycling program is positive in every way.

oysters in Chesapeake Bay
Oysters shells curing in the sun

Shells are trucked to a depot in Maryland or the Virginia Institute of Marine Science beside the York River. A volunteer tips them on a hopper for conveyance through a tumble washer and bagging to cure in the sun for a year, eliminating the last traces of condiments from your meal. The happy, hot and sweaty team beside the river is, alas, not reassembling this year because of the coronavirus contagion.

oysters in Chesapeake Bay
Oyster gardening

Cured shells are loaded in tanks of brackish water to which larvae (‘spat’) are introduced from external suppliers. The spat can attach to hard surfaces like stone or concrete, but they prefer old shells, like the reefs of old. Young oysters are then dropped in sanctuary areas of the Bay or its creeks and rivers or oyster gardeners raise them for a year in cages where they grow faster and are protected before reaching their final destination. The goal is to deposit 10 billion oysters by 2025, an effort requiring over 21,000 hours of volunteer time.

oysters in Chesapeake Bay
Oyster lovers beside the York River

Not only will future diners and watermen benefit but the whole ecosystem. It is a story of a keystone species. In purifying 50 gallons of water a day, each oyster reduces dissolved nitrogen and phosphorus and, hence, the risk of dead zones from algal blooms. Their colonies provide important habitat for fish and crabs too. The early explorers adopted the Algonquin name for Chesapeake, meaning great shellfish bay,  and perhaps one day it will be apt again.

The Sound of Noise & Silence

Among many things we will remember after the coronavirus pandemic, the world was quieter than normal. When I compared a busy avenue-street intersection in Manhattan before and during the lockdown, I found a 6 decibel (dB) difference, four-fold in amplitude. (The vast range of sound detected by the human ear needs the logarithmic scale.) A lower density of traffic on the ground, underground and overhead was mostly responsible, with contributions from building work, human voices, and so on. In suburbia, it is weed whackers, chainsaws, and trucks that make most of the racket, and sometimes neighbors too! You can check out a noise map for your region and community here.

Human ear and listeningI can’t think of any virtues for noise, though we don’t agree on the main offenders. Objections are sometimes muted by vested interests. Noise is in the ear of the beholder. Sounds that some heads perceive as musical turn others in disdain or even pain. I remember marveling at the virtuosity of nightingales singing through the night in Languedoc. The volume can reach 95 dB, above the threshold of harm for human hearing.

… That thou, light-winged Dryad of the trees

In some melodious plot

Of beechen green, and shadows numberless,

Singest of summer in full-throated ease …

John Keats: Ode to a Nightingale

Music is mostly regarded as the antithesis of noise, but commonly causes hearing loss. Rock music at concerts and through headphones, for instance, but players of classical music are also at risk, especially French horn players, and when did you see them wearing ear protection? A trombone and trumpet can even register around 110 dB.

The world gets ever noisier, affecting mental well-being and wildlife. The background soundscape can swamp bird song and amphibian calls needed for wooing mates and defending territories, and sound from shipping and industry is conducted faster and farther through water, harming marine life. Even national parks can be noisy. I registered 65 dB at a car park in Yellowstone and had to hike far from human activity to find a nadir of 30 dB, equivalent to a soft whisper from signing leaves and boughs in still air.

We may seek quiet places for peace, but, please, not too quiet. Plunging below 30 dB is strange and uncomfortable, though few people experience it. When I sat in an anechoic chamber in a lab the ringing in my ears was unpleasant, like so much static (tinnitus). Exploring a labyrinthine cave was probably as silent as outer space, but I never noticed discomfort one day deep underground because I was lost and focused on finding a way out! Just as our brains can blot out noise, they can filter out silence too.

While noise irritates, silence is fascinating, even when it makes us feel uncomfortable. When John Cage’s enigmatic 4’33” composition was performed in 1952, the audience heard the soloist close the piano keyboard for the 3 movements. That’s all, except it wasn’t strict silence—someone coughed and there was a ripple as another suppressed a giggle. Some people interviewed afterwards said they felt insulted or cheated, whereas others said it made them watch and listen more intently than usual. I never heard this composition live, although I often listen in solitude or helped by watching dogs teach alertness to everything around, even when they seem to be dozing. May a quieter planet continue to reign after the pandemic.

 

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