Blogs from our Scientific Researchers

Carnegie Museum of Natural History is home to active research and vast scientific collections. Our scientific researchers regularly contribute to the blog at the museum.

February 16, 2024 by Erin Southerland

World Pangolin Day 2024 – The Mysterious Mammalian “Wishbone”

by John Wible

World Pangolin Day 2024 is on February 17, a day to raise awareness of pangolins or scaly anteaters, one of the most unique and endangered mammals on Earth. Their scales are harvested for traditional medicines that see them as cure-alls, but their scales are made of keratin like your fingernails and hair. Their scales are as medicinally effective as biting your nails.

Although I will get to pangolins, I am starting with our feathered avian friends. Birds have a Y-shaped bone in their chest called a furcula (Latin for little fork). It is part of the flight apparatus and is thought to be formed by the fusion of the right and left clavicles (our collarbones). However, some researchers think it might be a different bone called the interclavicle, which in mammals is only found in monotremes, the egg-laying mammals. Some non-avian dinosaurs have a furcula, which is part of the evidence placing them on the bird family tree. The furcula is commonly called the wishbone because of the practice of making a wish on the bone! You grab one arm and someone else grabs the other; both make wishes and then pull; whoever gets the larger piece will have their wish come true.

Chicken furcula. Photo credit: Clyde Robinson/Flickr Creative Commons

In celebration of World Pangolin Day, I want to introduce you to a mammal “wishbone.” If you search through the mammalian literature, you will not encounter a bone identified as a wishbone. Nevertheless, a small, select group of mammals have a pair of bones that looks, to me anyway, like a furcula. Here is an example.

*Lower jaw of the northern tamandua,* Tamandua mexicana. American Museum of Natural History 23437 made from CT scan data by Hannah Barton, University of Pittsburgh.

The lower jaw, the mandible, is made up of right and left bones called dentaries. They meet on the midline at the chin. In humans, the right and left bones are filled with teeth, fused on the midline, and don’t look like a furcula! The northern tamandua from Central America differs in that there are no teeth, the right and left bones are held together only by soft tissues, and it looks like a furcula! How does the tamandua survive without teeth? Tamanduas are social insect feeders (ants and termites) that swallow their prey whole; tamandua parents don’t have to worry about their kids chewing with their mouths open. Now, although the tamandua lower jaw looks kind of like a wishbone, when pulled apart there won’t be a winner as the split will be down the middle with the two halves the same size.

The vast majority of the 6,500 species of living mammals have teeth; some have dentaries fused like humans and some have them unfused like the tamandua. Of the 6,500 species, there are 31 that are toothless as their normal condition. These 31 fall into two camps: 15 are baleen whales, including the Earth’s largest animal, the blue whale, which are filter feeders; and 16 are social insect feeders like the tamandua. However, all 31 have a mandible that is reminiscent of an avian wishbone. The 16 social insect feeders are from three unrelated lineages that have convergently adapted to eating ants and termites. The three lineages are:

Spiny anteaters or echidnas (monotremes) found in Australia and New Guinea (four species).
True anteaters (myrmecophagids) found in South and Central America (four species including two kinds of tamandua).
Pangolins (pholidotans) found in Africa and Asia (eight species).

The mandibles of the #1 and #2 look like that of the northern tamandua. The left and right sides are not fused and the mandible is skinny in the front and larger in the back where it articulates with the skull. #3, the pangolins, are really different. The left and right sides are fused at the midline and the mandible is larger at the front.

*Lower jaw of the Sunda pangolin,* Manis javanica, United States National Museum 144418 made from CT scan data by the author.

*Skull of the Sunda pangolin,* Manis javanica, United States National Museum 144418 made from CT scan data by the author. Red arrow points to the two bony mandibular prongs in the close-up.

The other very odd thing about the pangolin mandible is that it has a pair of bony prongs at the front that look somewhat like teeth (red arrow). Doran and Allbrook (1973: Journal of Mammalogy) dissected the pangolin tongue and reported that the lower lip was attached to these prongs, but they did not illustrate this or explain it further. Pangolins are clearly doing something different with their mandible than the tamanduas and echindas are, but what, I don’t know. Whatever it is, it has been around in pangolins for at least 35 million years! There was a pangolin that lived in the American West during the late Eocene named Patriomanis americana and it has a set of mandibular prongs just like those in the Sunda pangolin shown here. The other difference with the pangolin mandible is that when subjected to a wishbone pull, it might not break down the middle and be more like a furcula.

I have left the baleen whales until the end. Are their mandibles more like the tamandua, the pangolin, or neither?

*Mandible of the blue whale,* Balaenoptera musculus. Only the left dentary is on display in the Hall of North American Wildlife at Carnegie Museum of Natural History. The author manipulated the photograph to create the world’s largest “wishbone.”

Baleen whales are more like the tamandua with the right and left sides unfused and the mandible larger in the back than the front. If you were able to do the wishbone pull on the blue whale, there would be no winner and someone would likely lose by throwing their back out!

John Wible is Curator of Mammals at Carnegie Museum of Natural History.

The Hermit Crab and the Moon Snail

by Timothy A. Pearce and Mandi Lyon

When a snail needs a larger shell, it simply grows its shell larger, continuing the spiral. However, when a hermit crab needs a larger shell, it must find a larger shell to move into. Consequently, hermit crabs depend on snails to provide housing. Hermit crabs have soft abdomens, which are vulnerable to predators, so they keep their abdomens protected inside of snail shells.

There are amusing stories of several hermit crabs lining up in order of shell size, in a type of pecking order. When a new shell becomes available, the hermit crab highest on the pecking order holds onto the new shell and keeps a tight grip on its current shell as well. It tries out the new shell, and if it is an improvement, the crab will quickly move from one shell to the other, releasing the old shell. The old shell then becomes available to the next crab in the pecking order who examines it, and so on down the line.

Apparently, hermit crabs don’t kill snails to get the shells, but instead appear to move into already empty shells.

This series of photos was taken in the evening of August 12, 2017, at Amherst Shore Provincial Park on the Northumberland Strait in Nova Scotia. The photos show a hermit crab wearing the shell of a Dog Whelk (Nucella lapillus) encountering a Spotted Northern Moonsnail (Lunatia triseriata). The entire interaction took about a minute or so. The hermit crab approaches (Fig. 1) and climbs onto the moon snail (Fig. 2). The snail pulls its body into its shell and blocks the shell opening with its horny operculum, like a door that shuts the opening tightly (Fig. 3). The crab flips the shell over and the reddish colored operculum is visible (Fig. 4). The crab probes into the aperture (Fig. 5). Then the crab walks away (Fig. 6), evidently convinced that the shell is not available.

It’s hard to tell whether the hermit crab feels crowded in its current shell; it looks fine to us, but maybe hermit crabs are always on the lookout for better accommodations. The crab approached from the snail’s backside, so perhaps the crab didn’t notice that the snail is alive. The crab flipped the shell over, probed into the aperture where it bumped into the operculum.

How fortunate to be able to witness such an interaction, and to have a camera to record the episode!

*Fig. 1. Hermit crab approaches snail. Photo by M. Lyon.*

*Fig. 2. Hermit crab climbs onto snail. Photo by M. Lyon.*

*Fig. 3. Snail withdraws into shell blocking opening with operculum. Photo by M. Lyon.*

*Fig. 4. Hermit crab flips the shell over (note reddish operculum). Photo by M. Lyon.*

*Fig. 5. Hermit crab probes into the shell aperture, knocking on the door-like operculum. Photo by M. Lyon.*

*Fig. 6. Hermit crab walks away. Photo by M. Lyon.*

Mandi Lyon is the Program Manager for Schools & Groups and Timothy A. Pearce is Curator of Mollusks at Carnegie Museum of Natural History.

Groundhog Day 2024: Punxsutawney Phil’s Alpine Cousin

by Suzanne McLaren and John Wible

Beginning in 1887 in Punxsutawney, Pennsylvania, the celebration of Groundhog Day has made the groundhog (Marmota monax) a familiar animal to people who live far beyond the range of this species. While this large ground squirrel may get the most publicity, especially on February 2^nd every year, there are twelve related species that live elsewhere in North America, Europe, and Asia. In Europe, the Alpine marmot (Marmota marmota), which lives in mountainous areas of the continent’s central and western regions, is particularly well-known. Like the groundhog, it spends most of the year fattening up so that it can survive the winter months by hibernating.

two alpine marmots — *Credit: Sylvouille at French Wikipedia. – Transferred from fr.wikipedia to Commons., CC BY-SA 1.0*

While our local groundhog leads a more solitary existence, the Alpine marmot lives in a communal setting that includes a single breeding pair and around 15-20 of their offspring. They live in underground burrows that are passed down for generations within the family group, expanding over time into complex systems of tunnels. The tunnels eventually lead to a large chamber or den, where the entire family hibernates during the winter months. This concentrates body heat among the group and helps younger individuals to survive. Similar to prairie dogs, family members are friendly and playful with each other, grooming and touching noses when they greet. One individual, serving as a guard at the mouth of the burrow, will give off a loud whistle, to warn the rest of the family about the approach of an enemy – either a predator or even a non-family member of its own species.

Humans have hunted this species for hundreds of years for its meat. They are still hunted by the thousands for sport in Switzerland and Austria, with the large, ever-growing, yellowish-orange upper incisors sometimes displayed on hunters’ belts.

alpine marmot skull — *Picture of Alpine marmot skull showing large incisors, Klaus Rassinger und Gerhard Cammerer, Museum Wiesbaden, CC BY-SA 3.0, via Wikimedia Commons*

It is also reported that rendered Alpine marmot fat is still sought after as a folk remedy for arthritis. It is not taken internally but rubbed on sore joints.

two glass containers of rendered marmot fat — *Picture of rendered marmot fat. Credit: H. Zell, CC BY-SA 3.0*

Perhaps the most surprising anecdote about the interaction of humans and the Alpine marmot is the use of the animal for entertainment, though not for weather forecasting like Punxsutawney Phil. Stories of a trained Alpine marmot on a leash, accompanying a “hurdy-gurdy man”, somewhat like the organ grinder and his monkey, date to at least the mid-1700s as evidenced by François Hubert Drouais’ painting Les Enfants d’ Ilustre Naissance. Here, two boys sit together, one playing the hurdy-gurdy, a stringed instrument, and the other holding a dancing marmot on a leash. The traveling entertainer carried his marmot from town to town in a box. If you’ve ever witnessed the belligerent behavior of a local groundhog you might find it hard to believe that any Pennsylvania groundhog, other than Punxsutawney Phil, would allow itself to be led around on a leash or kept in a box!

picture of the painting "The Children of the Duc de Bouillion" by Francois-Hubert Drouais — Credit: François-Hubert Drouais, Public domain PD-US, via Wikimedia Commons

Suzanne McLaren is Collection Manager of Mammals and John Wible is Curator of Mammals at Carnegie Museum of Natural History.

2023 Rector Christmas Bird Count Results

by Annie Lindsay

*American Woodcock. Photo by Powdermill Avian Research Center.*

For a few hours before dawn on the chilly morning of December 16, several intrepid birders scoured the Rector Christmas Bird Count circle for owls, and with a bit of luck, counted four species. Eastern Screech-Owl is a common, year-round resident and a respectable 14 individuals were heard calling that morning, in addition to one encounter each of Great Horned Owl, Barred Owl, and Northern Saw-whet Owl.

Once the sun rose that morning, the owlers were joined by many other birders to spend the day systematically searching for and tallying all the birds they could see and hear throughout the day. The Christmas Bird Count (CBC) is an annual citizen science tradition that began in 1900 with the goal of counting all the birds that participants encounter within an established 15-mile diameter circle on a selected day between December 14 and January 5. The Rector count, centered just northwest of Powdermill Nature Reserve, covers a variety of habitats and elevations spanning from the Chestnut Ridge to the Laurel Ridge, and has been going strong since 1974. Because of the diversity of habitats and the dedication of participants, Rector CBCers have totaled 132 species within the circle, including a new species added this year.

*Rusty Blackbird. Photo by Powdermill Avian Research Center.*

The Rector count circle is divided into sectors, and this year’s 43 participants fanned out to cover as much territory as they could within their assigned sectors, some opting to hike trails in the state parks and forest, some traveling the roads by car, stopping periodically to listen and watch, and eight birders counted the species they saw visiting their feeders and yards. At the end of the day, everyone gathered at Powdermill for the tally dinner, an evening to chat about the day’s events, share a delicious meal, and to add up the birds each group counted. This year’s total was above average with 6,131 individuals of 76 species tallied, surpassed in recent years only by 2021, a year with unseasonably warm temperatures extending quite late into the fall that garnered several species not normally expected to persist into December. Many species set new high-count records this year, including Canada Goose, Black Vulture, Red-tailed Hawk, American Woodcock, Red-bellied Woodpecker, Yellow-bellied Sapsucker, Hairy Woodpecker, Pileated Woodpecker, Carolina Wren, Eastern Bluebird, Northern Mockingbird, and Red-winged Blackbird. Although some of these high counts likely can be attributed to increased effort and number of participants, almost all of these species seem to be expanding their ranges northward, or are occurring in southwestern Pennsylvania in greater numbers, often year-round, a trend ornithologists have been noticing in recent years.

*Pileated Woodpecker. Photo by Alex Busato.*

Excitement is always high at the tally, and this year was no exception. Highlights of the count were plentiful as participants shared photos and stories about their birds-of-the-day. One group found two Ruby-crowned Kinglets (nearly matching the count’s high total of three set in 2021) and a massive flock of 915 Canada Geese, which was the bulk of the day’s record-setting total. Another group found an Eastern Phoebe, a species recorded only twice before on the Rector CBC, perched in a tree pumping its tail up and down. Three participants photographed a Rough-legged Hawk, a species uncommon enough that they knew they would have to “prove” their identification, soaring over farm fields while driving to get lunch. And another group reported a flock of 150 Red-winged and 20 Rusty Blackbirds, setting a record for Red-wingeds and the highest count of Rusties since the mid-1990s. They also spotted an American Woodcock, a new species for the count, doing its bobbing walk in a wet spot along a road.

*Rough-legged Hawk. Photo by Mark McConaughy.*

One more notable finding of the day was three leucistic Red-tailed Hawks. At least one had been spotted at the edges of fields near Powdermill for much of 2023, but on the day of the count, two different birds, with varying amounts of white, were spotted and photographed in those fields, and a third was spotted many miles to the northwest in a different sector. The word “leucistic” refers to lack of pigment, and these leucistic birds have one or, in the case of these particular hawks, many white feathers. Finding one leucistic bird is uncommon, but three relatively large birds showing this same coloration is quite rare.

*Leucistic Red-tailed Hawk. Photo by Mark McConaughy.*

As we wrap up the 124^th Christmas Bird Count season and submit the Rector count’s data to the National Audubon Society, we thank all participants for their commitment to the birds and look forward to next year’s count!

For more information about the Christmas Bird Count and to see how the data are used, please visit: https://www.audubon.org/conservation/science/christmas-bird-count

Final 2023 Tally:

*Canada Goose – 1009

Mute Swan – 4

Tundra Swan – 1

Wood Duck – 1

American Black Duck – 13

Mallard – 74

Bufflehead – 2

Hooded Merganser – 11

Common Merganser – 3

Ruddy Duck – 6

Ring-necked Pheasant – 7

Wild Turkey – 14

Pied Billed Grebe – 6

*Black Vulture – 55

Turkey Vulture – 80

Northern Harrier – 1

Sharp-shinned Hawk – 1

Cooper’s Hawk – 2

Black Eagle – 2

Red-shouldered Hawk – 9

*Red-tailed Hawk – 66

Rough-legged Hawk – 1

Killdeer – 3

*American Woodcock – 1

Rock Pigeon – 37

Mourning Dove – 90

Eastern Screech-Owl – 14

Great Horned Owl – 1

Barred Owl – 1

Northern Saw-whet Owl – 1

Belted Kingfisher – 8

Red-headed Woodpecker – 6

*Red-bellied Woodpecker – 102

*Yellow-bellied Sapsucker – 16

Downy Woodpecker – 66

*Hairy Woodpecker – 28

Northern Flicker – 17

*Pileated Woodpecker – 38

American Kestrel – 2

Eastern Phoebe – 1

Blue Jay – 287

American Crow – 764

Common Raven – 25

Carolina Chickadee – 1

Black-capped Chickadee – 311

Tufted Titmouse – 212

Red-breasted Nuthatch – 7

White-breasted Nuthatch – 144

Brown Creeper – 8

Winter Wren – 3

*Carolina Wren – 86

Golden-crowned Kinglet – 60

Ruby-crowned Kinglet – 2

*Eastern Bluebird – 191

Hermit Thrush – 5

American Robin – 85

*Northern Mockingbird – 19

European Starling – 794

Cedar Waxwing – 45

Yellow-rumped Warbler – 7

American Tree Sparrow – 7

Field Sparrow – 5

Fox Sparrow – 1

Dark-eyed Junco – 411

White-throated Sparrow – 105

Song Sparrow – 117

Swamp Sparrow – 12

Eastern Towhee – 3

Northern Cardinal – 168

*Red-winged Blackbird – 151

Rusty Blackbird – 20

House Finch – 110

Purple Finch – 1

American Goldfinch – 90

House Sparrow – 61

Total Species: 76

Total Individuals: 6,131

*asterisk indicates high total for count

Annie Lindsay is Banding Program Manager at Powdermill Nature Reserve, Carnegie Museum of Natural History’s environmental research center.

Collected On This Day: Witch Hazel, January 1923

by Mason Heberling

witch hazel branch, buds, and leaf on an herbarium sheet

This specimen of common witch hazel (Hamamelis virginiana) was collected in January 1923 in Beaver County, Pennsylvania “East of Ambridge” by H.W. Graham. Herbert W. Graham (1905-2009) was an “Assistant” in Botany at the Carnegie Museum from 1925-1929 while he was a student at the University of Pittsburgh who later became an oceanographer at the Woods Hole Oceanographic Institution. During his time at the museum, he collected many specimens, often with his brother, Edward H. Graham, who was also an Assistant in Botany, later curator (1931-1937) and later, a well-known conservationist with the US Department of Agriculture. The Graham brothers went on expeditions to the Sonoran Desert in the late 1920s, collecting specimens and information that was used to create the desert diorama that remains in the museum’s Hall of Botany today.

This specimen has a “bits and pieces” feel to it, but shows what the plant looks like in winter, with branches, buds, a leaf, and even including a nice cross section cut out of the stem. The leaf is in great shape, which makes me question whether the leaf was truly was collected in January, when the leaves are usually dry and crumbled from the wrath of winter.

The specimen was simply collected in “January 1923” with no note on the day of year. I feel that coming off a holiday break (what day is it?). But more seriously, it reminds us that many specimens of the past were collected for different purposes with many of their uses today unanticipated. For instance, collectors today would certainly record the calendar date of collection, valued just as much as information on the location it was collected, as scientists routinely use specimens to date information to understand the seasonal timing of leafing, flowering, and fruiting with changing environmental conditions over time.

The leaf is a nice touch, too. It indicates that at least some leaves were still around in the winter of 1923, and it is quite possible they were even still connected to the stem. Though this species is deciduous (drops its leaves seasonally), common witch hazel has been known to sometimes hang onto some dead leaves on branches through winter. This phenomenon is known as “marcescence.” Why this happens isn’t fully known. Read more here.

You can find this specimen and 588 others of the species in the Carnegie Museum herbarium here.

Above: Witch hazel exhibiting marcescence, with last year’s leaves still attached in early spring (photo taken March 23 2021 at Powdermill Nature Reserve)

Below: Witch hazel’s magnificent autumn blooms. Unlike many woody plants in our region that bloom in spring as leaves are emerging, this species blooms in fall, as its leaves are dropping! (Photo taken October 29 2022 in New Kensington, PA.)

Mason Heberling is Associate Curator of Botany at Carnegie Museum of Natural History.

Oysters Swim Towards a Siren Soundscape

by Sabrina Spiher Robinson

illustration of a walrus and a person on a beach looking at oysters with feet — *Illustration by Sir John Tenniel. Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License.*¹

“’O Oysters, come and walk with us!’

The Walrus did beseech.

‘A pleasant walk, a pleasant talk,

Along the briny beach:

We cannot do with more than four,

To give a hand to each …

Four other Oysters followed them,

And yet another four;

And thick and fast they came at last,

And more, and more, and more—

All hopping through the frothy waves,

And scrambling to the shore …

‘O Oysters,’ said the Carpenter,

‘You’ve had a pleasant run!

Shall we be trotting home again?’

But answer came there none—

And this was scarcely odd, because

They’d eaten every one.”

In 1872, Lewis Carroll included the poem “The Walrus and the Carpenter” in his classic book Through the Looking Glass. The Walrus calls out to the oysters to join him and the Carpenter on a walk along the seashore; the young oysters don’t know any better and come to join him. Eventually, all the oysters are eaten up. But can one really sing a siren song to make an oyster come to them? An informed answer to this question requires some background knowledge information about an underappreciated form of wildlife.

oyster shells on cultch in a box — *The favored subsurface described as “cultch” is depicted in this cluster of oyster shells of the species* Crassostrea virginica.

Oysters live in reefs, submerged ridges or mounds of stable material, and baby oysters prefer to settle on a base — called “cultch” — of old oyster shells. Where conditions are favorable, oysters have plenty of company. When a team of researchers investigated the diversity of oyster reefs in the Gulf of Mexico, they detailed the incredible number of creatures that live on the reefs where oysters form: 115 species of fish and 41 species of crustaceans made the Gulf oyster reefs their homes, at very high densities and in communities containing up to 52 species at a time. Other researchers have documented multiple corals, mollusks, and worms that live primarily on oyster reefs. Unfortunately, erosion from coastal development, wetland destruction, unsustainable harvesting, and pollution have decimated populations of the Atlantic coast’s native oyster, Crassostrea virginica, which is bad news for coastal marine habitats in general.²

The importance of oyster reefs as marine habitats for multiple species is only one reason to preserve and reconstruct them. Oysters, as filter-feeding animals, provide an incredible service to the water quality of the estuaries they inhabit. They are also, of course, an important food source along America’s east coast.

The complications of rebuilding and repopulating oyster reefs are many. Pollution must be reduced, especially the run-off of agricultural fertilizers. Such fertilizers “enrich” underwater environments in a process called eutrophication.

Eutrophication causes massive blooms of algae that set off a chain of events disastrous for bodies of water and their inhabitants: the algae can release toxins on its own, but most commonly it overwhelms host ecosystems by blocking sunlight and killing all of the other plants in the water. Eventually the algae die too, and as all these dead plants decay, eaten away by multiplying bacteria that use up what little oxygen is left, dead zones form that suffocate underwater animals. This decay also lowers the pH of the water, leading to acidification that harms and kills animals (especially mollusks, whose shells dissolve in a very acidic environment). Additionally, if sediment erosion is not reduced, these water-borne materials eventually bury and suffocate oysters.

Oyster bed substrates that have been destroyed by human construction or aggressive commercial dredging can be replaced with cultch that is attractive to baby oysters. However, baby oysters must be recruited to the rebuilt reefs, either from the natural population of oyster larvae, or from hatchery-grown larvae reintroduced to the environment.

So, how to attract a baby oyster to your newly constructed oyster reef? First, let’s consider the life cycle of C. virginica, and the critical importance of age range in young oyster populations. In the first year of their adult lives, oysters are male. At certain times of the year, in response to pheromonal cues from their fellow oysters on the reef, they release clouds of billions of sperms. Older oysters on the reef, creatures transitioned into females after a year or two of life, release millions of eggs into these clouds of sperm. About two days after an egg is fertilized, the oyster larvae have become what are called veligers, and they begin to feed on particles in the water and to seek a place to call home. During this time, they develop a foot, and once they arrive on some promising substrate, they can crawl around, looking for just the right spot. At this point they are called spat. Soon the spat lose their feet and cement themselves to the spot they will call home for the rest of their lives, which can be more than a dozen years in the wild.

small boxes of oyster shells — Crassostrea virginica, from the CMNH collection, multiple shells that look completely different, but represent a single species. Epicures report taste differences according to where exactly each oyster lived.

It was long unknown how much choice an oyster veliger had in determining where it landed. Until the 1990s scientists thought that baby oysters had very little control over their movement in the water. In 2022, Australian scientists studying the Australian flat oyster, Ostrea angasi, proved that oyster veligers could very deliberately move to get to a surface they preferred to make their permanent home on.³

How this discovery occurred is of particular interest. The Australian researchers were testing the effects of soundscapes on oyster larvae, following experiments conducted in America in Pamlico Sound in North Carolina. Soundscapes are the collective sounds of a given environment: all the noises of human and non-human animal activity, along with environmental sounds of wind and water and precipitation. In 2014, researchers in North Carolina were experimenting with ways to attract oyster larvae to their newly built conservation reefs. They discovered that by recording the soundscape of a healthy oyster reef and playing it in the water, they attracted a much higher number of spat on experimental tiles near the recordings. Apparently, the baby oysters heard the sound of a healthy oyster reef and headed towards it to make their homes.⁴

How do oysters hear? Humans and other land animals hear through a system of air compression. Sound waves compress air in certain patterns, and tiny hairs within our ears translate those compressions into electrical signals that are then sent to the brain for further interpretation as sound. Underwater, animals hear through particle vibration: sound waves vibrate from particle to particle in the denser medium of water, where the particles are in direct contact with one another, even the water contained in the bodies of fish and invertebrates. Underwater animals have sensing structures that translate these vibrations into electrical signals that the animal then interprets in some way.⁵

Following up on the work of the North Carolina scientists, the Australian scientists confirmed in lab studies using underwater speakers in a completely currentless body of water, that oyster larvae were deliberately swimming towards the sounds of a healthy reef to settle. When they tried this technique on human-made conservation reefs, oyster recruitment increased on the artificial cultch — an important finding, since if baby oysters don’t find the newly deployed conservation reefs quickly, the reefs become covered in algae, making it very difficult for oyster spat to attach to them.⁶

And so, recording and replaying the soundscape of a healthy oyster reef — populated by snapping shrimp, oyster toadfish, and many other creatures that call a healthy oyster reef home — can help with the recruitment of baby oysters to human-made reefs for the purposes of conserving and growing the endangered population of C. virginica. Not only can oyster larvae “hear,” they can — and will — very deliberately swim toward the sounds of a healthy reef. And truly, who amongst us could deny the siren song of the snapping shrimp and the oyster toadfish?

Listen:

Coastal Conservatory

Center for Marine Sciences and Technology (CMAST)

Sabrina Spiher Robinson is Collection Assistant for the Section of Mollusks at Carnegie Museum of Natural History.

Notes:

Science Museum Group. Magic lantern slide depicting Alice’s Adventures in Wonderland, Walrus, Carpenter and Baby Oysters. 1951-316/11Science Museum Group Collection Online. Accessed 9 January 2024. https://collection.sciencemuseumgroup.org.uk/objects/co8362656/magic-lantern-slide-depicting-alices-adventures-in-wonderland-walrus-carpenter-and-baby-oysters-lantern-slide.
La Peyre Megan K., Aguilar Marshall Danielle, Miller Lindsay S., Humphries Austin T. Oyster Reefs in Northern Gulf of Mexico Estuaries Harbor Diverse Fish and Decapod Crustacean Assemblages: A Meta-Synthesis Frontiers in Marine Science, Vol. 6, 2019 https://www.frontiersin.org/articles/10.3389/fmars.2019.00666
Williams, B. R., McAfee, D. & Connell, S. D. Oyster larvae swim along gradients of sound. Journal of Applied Ecology, Vol 59, 2002, pp. 1815–1824 https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2664.14188
Ashlee Lillis, David B. Eggleston, DelWayne R. Bohnenstiehl Oyster Larvae Settle in Response to Habitat-Associated Underwater Sounds PLOS ONE 9(1). October 30, 2013 https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0079337#amendment-0
Nedelec, S.L., Campbell, J., Radford, A.N., Simpson, S.D. and Merchant, N.D. Particle motion: the missing link in underwater acoustic ecology. Methods Ecol Evol vol 7, 2016, pp. 836-842 https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/2041-210X.12544
McAfee, D., Williams, B. R., McLeod, L., Reuter, A., Wheaton, Z., & Connell, S. D. Soundscape enrichment enhances recruitment and habitat building on new oyster reef restorations. Journal of Applied Ecology, vol. 60, 2023, pp.111–120 https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2664.14307

World Pangolin Day 2024 – The Mysterious Mammalian “Wishbone”

by John Wible

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The Hermit Crab and the Moon Snail

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