These whales still use their vocal cords in the deep sea, but how?
News and notes about science
People have told stories of strange underwater sounds for thousands of years, but it took until the mid-20th century for scientists to pinpoint one of the causes: whales, singing and whistling and squeaking in the blue.
The means by which some whales make these sounds has remained a mystery. A study published last month in the journal Nature puts forth a new explanation, discovered thanks to a contraption that forced air through the voice boxes of three dead whales.
The voice box, or larynx, is an ancient organ. “It evolved when fish crawled out of the sea and animals needed a way to separate the air they’re breathing from the food they’re taking in,” said Coen Elemans, an author of the study and a professor of biology at the University of Southern Denmark.
The larynx functions like an antechamber to the windpipe, or trachea, with a flap of tissue called the epiglottis keeping food and drink from falling down the windpipe. A bit below the epiglottis, mammals have evolved additional folds of tissue, called vocal cords or vocal folds, which produce sounds when air exhaled from the lungs causes them to vibrate.
When the land-dwelling ancestors of whales returned to life in the sea, “they basically had to change the larynx, because when these animals are breathing on the surface, they need to expel lots of air really fast,” Elemans said. Vocal folds like those of land mammals could get in the way.
Toothed whales, such as sperm whales and dolphins, use their larynges like a cork to seal their airways; they evolved a way to produce sounds in their nasal cavities instead. But scientists suspected that filter-feeding baleen whales, including the musical humpbacks and the huge blue whales, still use their voice boxes.
These whales are too large to keep in captivity and tend to do most of their vocalizing too deep underwater for divers to collect ultrasound or MRI data. Instead, Elemans and his colleagues examined the next best thing: freshly preserved voice boxes dissected from three baleen whales that had died after stranding onshore, two in Denmark and one in Scotland. One was a humpback, one a minke, the last a sei.
The researchers attached the whales’ 2-foot-long voice boxes to a series of pipes and pumped air through them. At first, the voice boxes failed to make any noise. But when the researchers repositioned the larynx such that a fatty pad connected to it was vibrating against the vocal folds, the lab was filled with the sounds of a vocalizing whale.
In terms of excitement among the researchers in the lab, “on a scale of 1 to 10, it was an 11,” said W. Tecumseh Fitch, an author of the study and a professor of cognitive biology at the University of Vienna. This means of producing sound, with air squeezed between a cushion of fat and the vocal folds, has never been seen in another animal.
Joy Reidenberg, a professor of anatomy at the Icahn School of Medicine at Mount Sinai who was not involved in the study, said the experiment “changes our perspective on how sounds are made in these whales, and it perhaps shows us a mechanism which the whales might use to make more than one sound at the same time.”
She noted that the study was limited by the small number of whale voice boxes available for analysis, and that it may be fruitful to examine a greater number of specimens, especially adult male humpbacks that produce complex songs.
The researchers also created digital models to examine how constraints of lung capacity and water pressure might affect where and how the whales vocalize. The findings suggested that whales are limited to vocalizing in shallower waters. Unfortunately, this is also where noise from human activities such as shipping may interfere with the vocalizations of whales.
Christopher Clark, a professor emeritus of neurobiology and behavior at Cornell University who was not involved with the project, said that the complexities of sound traveling underwater suggested that whales’ ability to communicate might not be quite as hampered by shipping noise as the new study suggests.
And, he said, the study offers a “road sign” indicating where researchers should focus to learn about how and where whales actually communicate with one another.
— Kate Golembiewski
Scientists seek to explain frogs’ strange behavior
Faster than Gene Kelly tap-dancing in the rain, many species of poison dart frogs tap their middle toes on their hind feet so rapidly it can look like a blur. Three laboratories in different countries recently set out independently to understand why. Their studies all suggest that the presence of prey influences the toe-tapping, but the purpose of all that fancy footwork is still mysterious.
The research could help explain similar behavior in other frogs and toads, as dozens of species make some kind of toe or foot movement while hunting.
The latest study came from biologists at the University of Illinois Urbana-champaign. The researchers observed colorful dyeing poison dart frogs tapping up to 500 times per minute, or more than three times as fast as Taylor Swift’s “Shake It Off.”
When the frogs saw fruit flies in a petri dish but could not reach them, they tapped less frequently. This suggests that the tapping could relate to their ability to capture their meal.
But the team also found that toe-tapping had no relationship to the frogs’ success at catching prey. This “kind of confused us, and that’s what we’re still thinking about,” said Thomas Parrish, who worked on the study as an undergraduate with Eva Fischer, a biology professor.
Another hypothesis is that the toe-tapping vibrations could lure prey closer, similar to how turtles stick out their tongues to mimic worms and deep-sea angler fish attract meals with their glowing fishingrod-like protrusion.
— Elizabeth Landau
Cave pattern found in Patagonia is oldest rock art
In the stark inland desert of Patagonia in Argentina, there is a remote cave decorated with nearly 900 paintings of human figures, animals and abstract designs. Until recently, archaeologists had assumed that the rock art at this site, known as Cueva Huenul 1, was created within the past few thousand years.
But in a paper published in the journal Science Advances, archaeologists say that one of the cave’s most mysterious motifs, a comblike pattern, first appeared some 8,200 years ago, making it by far the earliest known example of rock art in one of the last places on Earth to be settled by our species.
Cave artists continued to draw the same comb design in black pigment for thousands of years, an era when other human activity was virtually absent at the site.
The cave art provides a rare glimpse of a culture that may have relied on this design to communicate valuable insights across generations during a period of climatic shifts.
“We got the results, and we were very surprised,” said Guadalupe Romero Villanueva, an author of the study and an archaeologist at the Argentine government agency CONICET and the National Institute of Anthropology and Latin American Thought in Buenos Aires. “It was a shock, and we had to rethink some things.”
Patagonia, located at the southern tip of South America, was not reached by humans until about 12,000 years ago. These early inhabitants thrived at Cueva Huenul 1 for generations, leaving signs of habitation.
Then, around 10,000 years ago, the area became more arid and hostile as a result of climatic shifts. The archaeological record in the cave likewise dried up for the next several thousand years, suggesting that the site was largely abandoned because of environmental pressures.