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domingo, 25 de octubre 2020
25/10/2020
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After the Vocal Repertoire of the Bottlenose Dolphin

by Natalia Piedrahita Tamayo
Journalist

 


Tursiops truncatus specimens are known as bottlenose dolphins. Photo credit: Jessica Patiño Pérez.

Between the Earth and Europa, a Jupiter moon, there is a distance of 628.3 million kilometers. It would seem like an impassable ocean of space and time.

Jessica Patiño Perez grew up among the mountains that surround Medellin, but dolphins —as far as they are from this place— have been her passion since childhood. Now, as a biologist from Universidad de Antioquia, she studies the sounds that these mammals make. She is particularly interested in the species Tursiops truncatus, also known as bottlenose dolphin.

Dolphins’ vocalizations are a like a hallmark through which they communicate with their relatives and groups. Moreover, vocalizations allow dolphins to orient themselves and locate their prey. The sounds produced by this species are related to its identity and skills.

Tursiops truncatus can be found in every ocean around the world, except those that surround Antarctica. It is also very common to find it in museums and aquariums. It is one of the most affected species by tourism because of its coastal habits”, Perez Patiño explained. She is currently taking a PhD degree in Conservation Biology from Massey University, in Auckland, New Zealand.

The abundance of this species around the world is directly proportional to the critical danger that threatens it in that country’s seas. They don’t reproduce often, and their population is very small. “In New Zealand, population numbers have dropped dramatically in the last 10 years,” the biologist explained, “especially in the Fiordland population, in the south. It has a particular conservation status in the world: critically endangered.”

How did a Colombian end up there? Her interest in these dolphins’ vocalizations —emissions of sounds— and the social networks they establish within their species started at Universidad de Antioquia, where she completed the Biology undergraduate program and met Professor Sergio Solari Torres. He accompanied the young student in her early research on the Guiana dolphin (Sotalia guianensis) in the Uraba gulf.

“Little was known about these dolphins in Colombia, but southern Uraba locals claimed that they often saw them. We appealed to every possible authority to rent motorboats and be able to see them,” Solari Torres recalled. “Jessica’s perseverance and passion overcame the obstacles and paid off: a research project on the presence of this species in the Turbo bays, at the mouth of the Atrato River.”

When she completed her bachelor’s degree, she did an internship in Brazil to study the Amazon river species (Inia geoffrensis) and tucuxi species (Sotalia fluviatilis). Nine months deep in the jungle without Internet or TV led her to focus on the field and analysis methodology to study these dolphins’ behavior. After that experience, a scholarship from Colfuturo (Colombian foundation that supports postgraduate students financially) took her to New Zealand to get a master’s degree, which brought her closer to the effects of human action on cetaceans in this Oceanian country.

Her academic experience has allowed her to observe the impact of anthropogenic noise on the cetaceans that inhabit the New Zealand coasts, as well as evaluate policies and restrictions for the protection of marine fauna.

Tourism is a great threat to marine mammals. The measures to restrict the effects of human action on marine life are not very effective. “What’s the use of restricting only commercial boats in a region where almost every family has a boat?”, asked Patiño Perez. For her, environmental policy and management plans cannot be limited by geography. She pointed out that species conservation measures must be global since marine fauna is naturally unaware of human boundaries.

Acoustic Analyses

The sonic universe of cetaceans is amazing. Its range is such that many songs sung by dolphins cannot be heard by the human ear, whose range limits go from 20 Hz to 20,000 Hz. Dolphins emit ultrasounds, which are above those limits. Such sounds can only be studied through acoustic analysis software that makes sound virtual to generate an idea of what those sounds may be like.

According to Patiño, the sounds produced by dolphins are of three kinds:

•    Whistles: They are the most common sounds. Dolphins use them to communicate, and they can be heard by humans. Evidence shows differences between the dolphins that live in the north and south of New Zealand, especially in amplitude and frequency. Scientists are studying whether these differences are due to social structures, environmental variables —such as temperature and depth— or physical characteristics of the areas they inhabit since the north is warmer than the south.
 
•    Clicking sounds: These are vocalizations dolphins use for echolocation and to find their prey. When they are produced, they bounce on the dolphin’s prey and back to it. Thus, the dolphin gets an idea of its surroundings.
 
•    Burst pulsed sounds: According to Patiño, these occur in social contexts, but they are also used for communication. These sounds have been studied the least of all. “These marine mammals can make clicking and burst pulsed sounds at the same time.”

 

Just like human language, dolphin language has variations”, Patiño Perez explained. “Just like there are words that are pronounced differently in certain regions, these mammals are also capable of making changes in their language”, she added.

These animals live in groups. In fact, this species’ social networks are another aspect of Patiño’s research. Thanks to photo-identification, which consists in taking pictures of these dolphins’ dorsal fins, she has been able to identify individuals, find out what groups they belong to and learn their life history in New Zealand’s North Island, Te Ika ā Maui.

“Groups aren’t the same all the time. When they are foraging, they make big groups. When they are resting, the groups are smaller. When they don’t spend much time in a certain area, I know they’re passing by, but I know three animals that are always together in that area”, she told us.

The Tursiops sp., or bottlenose dolphin, typical of the Australian western coast, has deep-rooted social practices. As a result, males make very complex alliances; so much so that they can be compared to those of human societies. These are relationships that last a lifetime. However, their interaction isn’t limited to their own species. They form groups with false killer whales, for example. There are many other species that they form mixed groups with.

 

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