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Distinctive sperm whale cultures reveal dramatic population shifts in the Galápagos

  • Researchers studied distinctive communication clicks among sperm whales to track several cultural clans in the Pacific Ocean.
  • Two clans dominated the waters near the Galápagos decades ago, but whales from two different clans have since moved in from across the Pacific basin.
  • Managing sperm whales may require tracking their populations culturally, rather than geographically.

Sperm whales wander great expanses of the sea, locking their culture between their lips and carrying it with them wherever they go. Their distinctive vocal traits allowed researchers to identify sperm whale cultures by their dialects, or “codas”—a rhythm of vocal clicks unique to each clan.

Now, this approach has revealed surprising movements of sperm whale groups across ocean basins. In a study published in Royal Society Open Science, scientists showed they could track each clan’s codas to discover shifts in their populations. This technique revealed that in just three decades, the seas near the Galápagos Islands experienced a complete cultural turnover of sperm whales.

Sperm whale in the Dominica. Photo Courtesy of The Dominica Sperm Whale Project

Between 1985 and 2014, study coauthor Dr. Shane Gero, a postdoctoral marine biologist at Aarhus University in Denmark, and his team recorded Galápagos sperm whale codas using underwater microphones. They identified individual whales by photographing their tails, which are distinguishable by natural crevices and bite marks.

A whale clan is composed of thousands of members that speak the same dialect. For the first 14 years of the study, clans that marine scientists called Regular and Plus-One lived in the Galápagos. Scientists recorded the consistent rhythm of clicks that are signatures of the Regular clan and the slight pause before the final click, a vocal tic distinctive to members of the Plus-One clan. But the whale numbers began to decline, and by the early 2000s the species had left the area.

 

https://mongabay-images.s3.amazonaws.com/16/SoundFile2PlusOnecoda.mp3?_=1

Sperm whales in the Plus-One clan have codas with a pause before the last click. An example of five regular clicks, a pause, and then a final click. Sound courtesy of Luke Rendell, University of St. Andrews.

 

https://mongabay-images.s3.amazonaws.com/16/SoundFile1RegularCodas6R.mp3?_=2

Sperm whales in the Regular clan have codas with regularly spaced clicks. An example of six regular clicks. Sound courtesy of Luke Rendell, University of St. Andrews.

 

Dominica sperm whales near the surface. Photo Courtesy of The Dominica Sperm Whale Project

In 2013 and 2014, the researchers identified two new clans called Short and Four-Plus in the Galápagos. Marine scientists knew these clans lived in other locations in the Pacific Ocean, such as in the Gulf of California or near the Marshall Islands, but their appearance thousands of kilometers away was startling.

According to Gero, this kind of cultural turnover is unheard of outside of humans. “It’s as if you had been going to Canada for 20 years and everybody spoke English and French, but then in the next 10 years nobody lived in Canada,” said Gero. “Then, you went back and everyone spoke Spanish and Portuguese.”

Other sperm whale researchers are intrigued by the results. “It is certainly fascinating that these animals show such a large turnover, but this opens up more questions, such as how typical is this in other locations?” said Elizabeth Slooten, a zoologist at Otago University in New Zealand who was not part of the study. “It would be cool for [the authors] to compare these sightings and sound recordings with a wider area across the Pacific.”

Figure 3: Sperm whales in the Dominica show their tails. Distinct crevices and bite marks help researchers identify individuals. Photo Courtesy of The Dominica Sperm Whale Project

When a marine environment changes, perhaps from whaling pressures or climate fluctuations, most animals prefer to stay in their habitats and adapt to the changes rather than move. For example, humpback whales can create entirely new songs after they interact with other whale groups moving into the area.

Sperm whales prefer to remain in their social groups and would rather wander great distances than change their cultures or behaviors, said Sarah Mesnick, an ecologist at the U.S. National Oceanic and Atmospheric Administration Southwest Fisheries Science Center in La Jolla, California, who was not part of the study. As scientists look to support these “cultural nomads of the sea,” Mesnick said, they may need to shift their focus from managing them based on geographic boundaries to managing them based on their cultural differences.

“Sperm whale cultures appear to endure dramatic environmental changes,” said Mauricio Cantor, a postdoctoral fellow at the Federal University of Santa Catarina, Brazil, and lead author of the study. “These cultural boundaries are not trivial or abandoned in the face of new challenges.”

As the ocean warms and as currents and food sources shift, the sea’s cultural nomads may be on the move once again—creating ongoing challenges for the conservationists who seek to manage them.

Citation:
Cantor, M., Whitehead, H., Gero, S., & Rendell, L. (2016). Cultural turnover among Galápagos sperm whales. Royal Society Open Science, 3 (10), 160615. doi: 10.1098/rsos.160615

Yasemin Saplakoglu is a graduate student in the Science Communication Program at the University of California, Santa Cruz. Other Mongabay stories by UCSC students can be found here.

Sperm whale in the Galápagos. Photo courtesy of Mauricio Cantor, Whitehead Lab, Dalhousie University