Humans, Dolphins Working Together to Fish
2023-02-05
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1A fishing community in southern Brazil has an unusual ally: wild dolphins.
2Stories of people and dolphins working together to catch fish go back thousands of years.
3But historians and storytellers have told the human side of the story.
4Until recently, it has been impossible to know how dolphins have benefited from the relationship.
5Now, sonar and underwater listening devices can follow them underwater and suggest an answer.
6In the coastal city of Laguna, scientists have used drones, underwater sound recordings and other tools to track dolphins.
7The scientists can see how local people and dolphins cooperate and benefit from each other's work.
8The most successful humans and dolphins are skilled at reading each other's body language.
9The research was published Monday in the journal Proceedings of the National Academy of Sciences.
10The Laguna residents work with wild bottlenose dolphins to catch schools, or groups, of silver fish called mullet.
11It is an alliance that has been recorded in local newspaper records going back 150 years.
12"This study clearly shows that both dolphins and humans are paying attention to each other's behavior, and that dolphins provide a cue to when the nets should be cast," said Stephanie King.
13She is a biologist who studies dolphin communication at the University of Bristol in Britain and was not involved in the research.
14"By working with the dolphins," the people catch more fish, "and the dolphins are more successful in foraging, too," King added.
15When it comes to fishing, dolphins and humans have different abilities.
16Mauricio Cantor is an Oregon State University marine biologist and co-writer of the study.
17In Laguna, the water is cloudy, so people are unable to see the fish, he said.
18But the dolphins use sounds to find them.
19As the dolphins herd the fish toward the coast, the people run into the water holding fish nets.
20"They wait for dolphins to signal exactly where fish are - the most common signal is what locals call 'a jump,' or a sudden deep dive," Cantor said.
21The researchers used sonar and underwater listening devices, or microphones, to track the positions of the dolphins and fish.
22Drones recorded the action from above, and GPS devices attached to residents' wrists recorded when they casted their nets.
23The more closely the people timed casting their net to the dolphins' signals, the more likely they were to catch a large amount of fish.
24When the nets fall in the water, it scares the fish.
25They then break into smaller schools that are easier for dolphins to hunt.
26Cantor said the dolphins sometimes also take one or two fish from the net.
27The Laguna residents group the individual dolphins as "good," "bad," or "lazy."
28The grouping is based on their skill in hunting and likelihood of cooperating with humans, said Cantor.
29The people get most excited when they see a "good" dolphin approaching shore.
30It is not clear how the Laguna cooperation first started.
31But it has survived many human and dolphin generations.
32The knowledge is passed down by experienced fishers and dolphins to the next generation of both.
33Still, the researchers in Brazil worry that the Laguna alliance may be in danger.
34Pollution threatens the dolphins and there are fewer local fisheries.
35Scientists hope that more attention to the unusual cooperation can help drive support to protect it.
36I'm Dan Novak.
1A fishing community in southern Brazil has an unusual ally: wild dolphins. 2Stories of people and dolphins working together to catch fish go back thousands of years. 3But historians and storytellers have told the human side of the story. Until recently, it has been impossible to know how dolphins have benefited from the relationship. Now, sonar and underwater listening devices can follow them underwater and suggest an answer. 4In the coastal city of Laguna, scientists have used drones, underwater sound recordings and other tools to track dolphins. The scientists can see how local people and dolphins cooperate and benefit from each other's work. The most successful humans and dolphins are skilled at reading each other's body language. 5The research was published Monday in the journal Proceedings of the National Academy of Sciences. 6The Laguna residents work with wild bottlenose dolphins to catch schools, or groups, of silver fish called mullet. It is an alliance that has been recorded in local newspaper records going back 150 years. 7"This study clearly shows that both dolphins and humans are paying attention to each other's behavior, and that dolphins provide a cue to when the nets should be cast," said Stephanie King. She is a biologist who studies dolphin communication at the University of Bristol in Britain and was not involved in the research. 8"By working with the dolphins," the people catch more fish, "and the dolphins are more successful in foraging, too," King added. 9When it comes to fishing, dolphins and humans have different abilities. 10Mauricio Cantor is an Oregon State University marine biologist and co-writer of the study. In Laguna, the water is cloudy, so people are unable to see the fish, he said. But the dolphins use sounds to find them. As the dolphins herd the fish toward the coast, the people run into the water holding fish nets. 11"They wait for dolphins to signal exactly where fish are - the most common signal is what locals call 'a jump,' or a sudden deep dive," Cantor said. 12The researchers used sonar and underwater listening devices, or microphones, to track the positions of the dolphins and fish. Drones recorded the action from above, and GPS devices attached to residents' wrists recorded when they casted their nets. 13The more closely the people timed casting their net to the dolphins' signals, the more likely they were to catch a large amount of fish. 14How do dolphins benefit? 15When the nets fall in the water, it scares the fish. They then break into smaller schools that are easier for dolphins to hunt. Cantor said the dolphins sometimes also take one or two fish from the net. 16The Laguna residents group the individual dolphins as "good," "bad," or "lazy." The grouping is based on their skill in hunting and likelihood of cooperating with humans, said Cantor. The people get most excited when they see a "good" dolphin approaching shore. 17It is not clear how the Laguna cooperation first started. But it has survived many human and dolphin generations. The knowledge is passed down by experienced fishers and dolphins to the next generation of both. 18Still, the researchers in Brazil worry that the Laguna alliance may be in danger. Pollution threatens the dolphins and there are fewer local fisheries. 19Scientists hope that more attention to the unusual cooperation can help drive support to protect it. 20I'm Dan Novak. 21Dan Novak adapted this story for VOA Learning English based on reporting by The Associated Press. 22______________________________________________________________ 23Words in This Story 24benefit - n. to gain a good result from some activity or relationship 25sonar (sound navigation and ranging) - n. a device that uses sound to find things underwater 26resident - n. a person who lives in a particular place for some time 27cue - n. to give a signal to start something 28cast - v. to throw a line or a net into the water to catch fish or other animals 29forage - v. to look for food or supplies 30herd - v. a group of certain kinds of animals such as cattle, sheep, goats and whales 31wrist -n. the joint between the hand and the arm 32lazy - adj. not liking or unwilling to do hard work