Dolphins are already known to possess human-like intelligence, but a new study suggests that the creatures are more like us than we realized.
In experiments, bottlenose dolphins (Tursiops truncatus) have been recorded “screaming” when trying to work together in response to increasing man-made noises.
Just as when humans scream to hear an air drill or fire alarm, dolphins’ vocalizations get louder, and they “shout” for a longer time, as the volume of the noise increases.
Fascinating footage from the experiments shows dolphins with audio recorders attached to their heads as they perform the task of pressing buttons underwater.
Bottlenose dolphins: fast facts
Bottlenose dolphins grow up to 13 feet (4 meters) in length and 1,300 pounds (590 kg).
They travel alone or in groups of about 12, but flocks of hundreds of dolphins have been spotted.
Common bottlenose dolphins develop individual whistles to communicate information regarding their location, condition, and identity with others.
They also taste each other’s urine to get to know others and if they are nearby.
Dolphins are known to be intelligent creatures who rely on their “chattering” vocalizations to hunt and reproduce.
But if noise from human activity such as digging and charging drowns out dolphin noise, it could negatively affect the health of dolphin populations.
The study, which was led by experts from the University of Bristol, is published today in the journal Current Biology.
“We show that man-made noise directly affects the animals’ success in working together,” said study author Stephanie King, from the University of Bristol.
If noise makes wild animal groups less efficient in performing cooperative actions, such as cooperative foraging, this could have important negative consequences for individual health, and ultimately the health of populations.
In general, dolphins make two types of sounds – “whistles” and “clicks”.
Clicks are Used for “echolocation” – a technique used by animals to locate objects such as food, obstacles, or potential dangers using reflected sound waves.
Meanwhile, whistles are used to communicate with other members of a species—and perhaps even other species, too.
It is already known that two dolphins in human care can work together to solve a collaborative task, understand the role their partner plays in the task, and use whistles to coordinate behavior.
In this study, the researchers wanted to see how “anthropogenic” noise — noise from human activity — might affect these abilities.
In experiments, University of Bristol researchers superimposed movement markers on bottlenose dolphins and exposed them to increasing levels of man-made noise. The dolphins had to work together to press their button underwater within 1 second of each other, while being exposed to increasingly higher levels of noise.
The experiments were conducted at the Dolphin Research Center (DRC) in Florida with two male bottlenose dolphins, Delta and Reese. The photo shows Delta wearing a DTAG – Motion and Sound Recording Mark
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A team from the University of Bristol found that individual dolphins responded strongly to the calls of “allies” that had come to their aid in the past.
But they were more likely to ignore those who hadn’t helped before — even if they appeared to be on friendly terms.
Examples of anthropogenic noise sources include drilling, airplanes, motor boats, traffic, and more.
The experiments were conducted at the Dolphin Research Center (DRC) in Grassy Key, Florida with two adult male dolphins, Delta and Reese, swimming in the lagoon.
Dolphins have already been trained to engage in cooperative behavior using fish rewards and social interaction.
Together with their international colleagues, the scientists outfitted Delta and Reese with suction cup tags that recorded their voices as they engaged in a collaborative mission.
During the task, the dolphins had to work together to press their button underwater within 1 second of each other, while being exposed to higher levels of noise from an underwater loudspeaker.
They used a variety of sounds, including the sound of the pressure washer the team in the Democratic Republic of the Congo uses to clean the lake.
To make it even more difficult, in some experiments one dolphin was held back for five to 10 seconds while the other was immediately released.
The researchers found that the dolphins produced louder and longer whistles to compensate for the increased noise levels — but they were less successful at the task as the noise got louder.
They found that from the lowest noise levels to the highest, the dolphin’s success rate dropped from 85 percent to 62.5 percent.
The experiments were conducted at the Dolphin Research Center (DRC) in Grassy Key, Florida, with two adult male bottlenose dolphins, named Delta and Reese. Dolphins have already been trained to engage in cooperative behavior, using fish rewards and social interaction
According to the experts, Delta and Reese compensated by changing the volume and length of their calls in their efforts to coordinate button presses.
Not only did the dolphins change the volume and duration of their noises, but also their body language.
As noise levels increased, the dolphins were more likely to reorient themselves to face each other, and they were more likely to swim to the other side of the lagoon to be closer.
“The subjects increased their orientation toward their partner as noise increased, but echolocation decreased,” the experts say in their paper.
“[This suggests] The dolphins were heading toward each other not to use echolocation to track their partner but to increase their chances of detecting their partner’s signals.
Directional hearing—the ability to locate a sound source—may have allowed them to separate their partner’s signals from noise signals due to the different spatial location of the two sound sources.
Just as when humans scream to hear an aerobic drill or a fire alarm, dolphins vocalize louder, and “shout” longer, with a higher volume of noise (the “apparent whistle output level” is a measure of the loudness of the whistle).
While the study offers a glimpse into the amazing lengths dolphins go to cooperate, it ultimately shows that they are less successful at doing so in the presence of human-generated sound.
“We’ve known for years that animals can try to compensate for increased noise in their environment by modifying their vocal behavior,” Sorensen said.
Our work shows that these adaptations are not necessarily sufficient to overcome the negative effects of noise on communication between animals working together.
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Dolphins whistle to each other as part of a male’s bonding ritual and rely on their “wings” to compete for the affection of potential mates.
Research has found that dolphins whistle to each other as part of a male’s bonding ritual and rely on “wing-men” to compete for the affection of potential mates.
Bottlenose dolphins could become more popular simply through vocal exchanges, experts at the University of Bristol said, which helps them maintain weaker but lively social relationships.
Not only that, but a separate study using the same data found that the more common a dolphin is among other males, the more successful it is when it comes to producing calves.
This research, which was led by the University of Zurich, found that groups of male dolphins would work together to compete with competing groups for access to females.
The most popular males in the group have the best mating success, it was found.