The Sound of One Walrus Clapping
Beginning in the late 2000s, Colleen Reichmuth and Ole Larsen visited the Six Flags Discovery Kingdom in Vallejo, California to hear a walrus. The male Pacific walrus named Sivuqaq was nearing sexual maturity, which meant it could soon be making the noise that male walruses make during the breeding season.
Dr. Reichmuth, a researcher at the University of California, Santa Cruz, drove a short distance to visit Sivuqaq. But dr. Larsen, a bioacoustician at the University of Southern Denmark, was a long way from Denmark.
Dr. Reichmuth and Dr. Larsen had come specially to hear Sivuqaq emitting the characteristic breeding noises of a male walrus: knocking, metallic gong-like blows and piercing whistles. But Sivuqaq, who stole the screen while appearing on “50 First Dates” with Adam Sandler and Drew Barrymore, was uncooperative. Some days he clapped his front fins a thousand times in a row underwater.
“It was distracting at first,” said Dr. Reichmuth. You and Dr. Larsen had come to the gong and knocking, not clapping. But they realized the incessant gossip was worth studying, and although it took a few years, they published their observations and records of the gossiping behavior on Wednesday in the Royal Society Open Science magazine. To the knowledge of the researchers, there is no documentation of wild walruses caught with a similar applause.
Dr. Reichmuth first met Sivuqaq as a puppy. The walrus was brought to Six Flags in 1994 when it was recovered from an Alaskan subsistence program. He shares the name Yupik for what is now the city of Gambell in Alaska. In captivity, the life of Sivuqaq has been documented in much greater detail than that of any wild walrus. He died at the age of 21 in 2015, several years after completing this research.
Dr. Reichmuth decided to study walruses after hearing a recording of a wild male walrus. The creature’s noises seemed to come straight from “Stomp,” the infamous off-Broadway percussive show. “It was like a noise on a construction site,” she says. “With a ram, or occasionally someone drops a large sheet of metal from a building.”
When Sivuqaq came of age, Dr. Reichmuth with Dr. Larsen worked together to measure the noise the walrus made during the rut, the time when male walruses feel the urge to reproduce. Scientists still don’t know exactly how walruses knock and ring the bell. One hypothesis is that blows can come from the walrus’s body and gongs can be generated from the air sacs of a male walrus, said Dr. Reichmuth.
The researchers installed hydrophones in Sivuqaq’s basin and filmed the walrus clapping with a high-speed black and white video camera. The video shows the walrus clapping its fins asymmetrically. Dr. Reichmuth compares it to hitting a catcher’s glove; By angling a fin to move like a blade in the water, the walrus reduces drag and can strike at a much faster rate. When the researchers slowed the frames, they discovered a bright spot that formed between the fins after clapping: cavitation bubbles that create the sound you make when you crack your knuckles.
“Walruses are able to clap so hard underwater that the water evaporates into a cloud of bubbles between their fins, which then collapses on itself to make an extremely loud noise,” said David Hocking, senior curator of vertebrate zoology at the Tasmanian Museum and Art Gallery, which was not involved in the research, wrote in an email. Dr. Hocking observed similar clapping behavior in wild gray seals during the breeding season, hypothesizing that this was a display of strength and fitness for rivals and potential partners.
The authors of the new study believe that Sivuqaq’s clapping has a similar function, since the walrus began to clap as it approached sexual maturity, and the behavior was often accompanied by a visible erection. “I think it’s hard for these animals to suppress them,” said Dr. Reichmuth, referring to Sivuqaq’s cacophonic urge to procreate.
Sivuqaq clapped at a steadfast pace: 1.2 seconds between claps, the same pace as the knocking noises he was making. And his clapping was loud; noticeable to people standing meters away from the ten centimeter thick glass walls of its armor. However, according to a 2003 study, the sounds of Sivuqaq never reached the full complexity of wild walrus breeding shows, which can consist of long patterned pulse trains of varying lengths and interrupted by bell-like sounds. In the eyes of Dr. Reichmuth produced the captured walrus song components but could not produce complex songs if it were denied the ability to hear and learn from the sounds of other adult walruses.
With a record from a walrus, it’s hard to tell if wild walruses will clap too. “Is that something a man did? Is it a new way of creating functionally similar behavior? ”Asked Eduardo J. Fernandez, an animal welfare scientist at the University of Adelaide, Australia who was not involved in the research. “This walrus appears to be breeding show,” he said.
Dr. Reichmuth and Dr. Larsen are working on a paper that analyzes the biological mechanisms behind Sivuqaq’s other, more popular, breeding sounds – which they originally came to Six Flags to study.