At Almost 500 Feet Below the Water, Experts Heard the Sounds of the Elusive Beaked Whale
One of the most misunderstood mammals. This is because these mysterious cetaceans are among the deepest diving whales and rarely spend time on the surface of the ocean. A new study has combined visual and acoustic monitoring to follow these elusive creatures in the Amazonas deep Foz basin off the northeast coast of Brazil.
The author of the Raphael Barbosa Machado study, researcher at the Federal University of Jeuiz de Fora in Brazil, said: “The motivation of this research was born from the need to expand knowledge on the biodiversity of cetaceans in Brazilian waters, with particular attention to deep diving species such as beaks”, in a press release. Machado and a team of Brazilian researchers have published their results The Journal of the Acoustic Society of America.
Learn more: The mysterious beak whale spade had always avoided humans – so far
Listen to the mainly silent whale
The withdrawal of whales was not an easy task. Animals can spend more than two hours under water, reaching depths of 3,000 meters (about 9,800 feet), where they feast on deep water and crustaceans. Machado and his colleagues knew that whales could be identified by their distinct echolocation impulses, which they use to speak with other whales.
Whales, however, remain silent up to 80% of their lives. Researchers believe that it is a cryptic defense mechanism to avoid detection by itinerant packages of killing whale predators. When the whales make noises, it is generally at depths less than 170 meters (about 560 feet), rather than closer to the surface of the ocean, posing a challenge for the team.
The researchers climbed aboard a 25 -meter long research tug (about 82 feet), Urano, and took off to systematically search for the basin. Their visual research involved two bellouts placed along each side of the Urano, which looked on the ocean for binocular whales. They sought the distinctive shape of the whales, the shape of the crescent -shaped head and the position of the dorsal fin.
The team combined this visual research with acoustic profiling. They deployed underwater microphones called hydrophones, placed in cages which they lowered to a depth of 150 meters (approximately 492 feet). These listened to the distinctive impulses with the frequency modulation of whales.
A dozen recordings reveal Brazilian beak whales
In the end, the team recorded 12 whale detections – three observations, eight audio recordings and an equal simultaneous recording. Audio recordings included 395 scald “clicks”. Interestingly, they did not record any whistles or supposedly “sounds buzz”, that these whales have already been recorded. The team concluded that this was probably due to the fact that these distinctive sounds were only used in limited social contexts and certain depths.
The team estimated that they had recorded at least three different species of beak whale during the study.
“This study provides the first documentation of the acoustic parameters of the beak whales in Brazilian waters,” Machado said in a press release. By capturing the most observations by acoustic surveillance, the study highlights the importance of following the most elusive species of our deep oceans using sound, a task that the team intends to continue through the South Atlantic.
“As the number of detections increases – in particular simultaneous visual and acoustic records – our ability to reliably associate acoustic signals specific to visually confirmed species will also improve,” said Machado in the press release. “It is essential to fill these shortcomings in knowledge to shed light on public policies and guide conservation and management efforts to protect these elusive species.”
Learn more: How do the whales hear their songs and other sounds if they have no ears?
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