A team of researchers in Italy, Portugal, Spain, France, Britain and the United States has demonstrated that remotely monitoring the acoustical structures of dolphin vocalizations can effectively detect “evolutionarily significant units” of the mammal — distinct populations that may be tracked for prioritizing and planning conservation efforts.
This finding, which has been presented this week at the 167th meeting of the Acoustical Society of America in Providence, Rhode Island, suggests that placing remote acoustical monitoring platforms on ocean buoys and the like may be a viable, low-cost and automated way of monitoring populations of dolphins and rapidly alerting ecologists to the threats that confront them.
“Acoustical changes can be used for constant and continuous monitoring of population belonging to endangered species,” said Elena Papale of the University of Torino, who led the research. “We found that [by remotely monitoring dolphin whistles], it is possible to distinguish between evolutionary significant units.”
The discovery emerged from a large, multinational collaboration that pulled together data from five research groups based in Italy, Portugal, Spain, Britain and France. Those groups were already monitoring dolphins for a number of existing scientific studies. Other groups in the United States collaborated by providing sound analysis equipment. Shepherding all these groups of people and the flood of data they produced was a challenge, Papale said, but the greater challenge was working out how to distinguish the flood of whistles from one group of dolphins from another.
Animal vocalizations have acoustic characteristics that reflect an organism’s genes, its adaptation to ecological conditions and the interactions between their genes and the environment. The differences between groups of dolphins within the same species may be slight and hard to detect however, because morphological features, ecological conditions and socio-behavioral aspects of the creatures influence the structure of whistle. The problem is also a dynamic one, since vocalizations may vary in short time scale.
So at the start of the research, it was not clear whether acoustical analyses alone would be able to tease apart the common threads for given groups of dolphins and differentiate between them.
Papale and her colleagues compared 123 sightings of three dolphin species from the Atlantic Ocean and the Mediterranean Sea (Stenella coeruleoalba, Delphinus delphis and Tursiops truncatus). They analyzed whistles from 49 hours of audio recordings made at the same time as the sightings and tested whether they could definitively identify dolphin populations by analyzing the acoustical parameters of the whistles.
This allowed them to correctly assign more that 82 percent of data to the correct dolphin population, based solely on the acoustic structure, a proof of principle that the acoustic structure of whistles can be used to monitor recent or rapid changes in the local population biology.
“More work is still needed to develop an automatic system for population recognition,” Papale said. She added that other research groups are focusing on the development of software but for the moment only for species-specific identification, not intra-specific recognition.
The life of a Great White Shark
The great white shark, known scientifically as Carcharodon carcharias, embodies the apex predator of the ocean. This majestic creature’s life is a testament to survival, adaptability, and the intricate balance of the marine ecosystem.
Born in the waters off coastal regions, a great white shark begins its life as a pup within the safety of nurseries, typically found in warm, shallow waters. The pups, measuring around 5 feet in length at birth, are immediately equipped with an innate instinct for survival.
As they grow, great whites embark on a journey, venturing into deeper and cooler waters, often covering vast distances across the ocean. These apex predators are perfectly adapted hunters, relying on their impressive senses to detect prey. Their acute sense of smell, aided by specialized sensory organs known as ampullae of Lorenzini, helps detect the faintest traces of blood in the water from several miles away.
Feeding primarily on seals, sea lions, and other marine mammals, great whites are known for their powerful jaws lined with rows of razor-sharp teeth. Their hunting techniques often involve stealth, utilizing their streamlined bodies to approach prey from below and striking with incredible speed and force.
Despite their fearsome reputation, great whites play a crucial role in maintaining the health of marine ecosystems. As top predators, they help regulate the population of prey species, preventing overpopulation that could disrupt the balance of the food chain.
Reproduction among great white sharks is a slow and careful process. Females reach sexual maturity between 12 and 18 years of age, while males mature earlier, around 9 to 10 years old. Mating occurs through complex courtship rituals, with females giving birth to a small number of live pups after a gestation period of about 12 to 18 months.
However, the life of a great white shark is not without challenges. Human activities, including overfishing, pollution, and habitat destruction, pose significant threats to their population. Additionally, despite their formidable presence, great whites are vulnerable and face dangers from entanglement in fishing gear and accidental bycatch.
Despite these challenges, great white sharks continue to inspire awe and fascination among scientists and nature enthusiasts. Their presence in the ocean serves as a reminder of the delicate balance and interconnectedness of marine life, emphasizing the need for conservation efforts to protect these magnificent creatures for future generations to admire and study.
Want to learn more about sharks? Visit The Shark Trust website: www.sharktrust.org
Book Review: Sea Mammals
This is a book packed with information about some of the most iconic and charismatic marine species. I have a particular soft spot for the pinnipeds, seals and sea lions, due to some incredible diving encounters over the years. So these were the pages I first turned to.
Once picked up this book is hard to put down. Polar Bears, Narwhal, Sea Otters, manatees, whales and dolphins adorn the pages with beautiful photographs and illustrations. Each turn of the page lures you in to discover more about a species you love, one you want to learn more about, some you have never heard of and even includes the details of fascinating animals that are sadly now extinct.
I think what I love most about this book is how it is organised. Rather than simply lump the animals into taxonomic groupings, they are put into chapters that tell you a story about them. Whether it is the story of their evolution, how they were discovered, their biology, behaviour or need for conservation. Once you have decided on an animal to delve deeper into, each species has its own story, as well as key information about size, diet, distribution, habitat and conservation status.
There is plenty to enjoy in this delightful book. Plenty to learn too. As the cold dark nights draw in, I can see myself delving into this book time and time again. This is a perfect gift for anyone that loves the ocean and its inhabitants. Or just treat yourself.
What the publisher says:
From the gregarious sea otter and playful dolphins to the sociable narwhal and iconic polar bear, sea mammals are a large, diverse, and increasingly precious group. In this book, Annalisa Berta, a leading expert on sea mammals and their evolution, presents an engaging and richly illustrated introduction to past and present species of these remarkable creatures, from the blue whale and the northern fur seal to the extinct giant sperm whale, aquatic sloth, and walking sea cow.
The book features more than 50 individual species profiles, themed chapters, stunning photographs, and specially commissioned paleo-illustrations of extinct species. It presents detailed accounts of these mammals’ evolutionary path, anatomy, behavior, habitats, and conservation. And because these are key species that complete many food chains and have the widest influence of all sea life, the book also offers insights into a broad variety of marine worlds today and in the future.
About the Author:
Annalisa Berta is professor emerita of biology at San Diego State University. A specialist in the anatomy and evolutionary biology of marine mammals, especially baleen whales, she formally described a skeleton of the early pinniped Enaliarctos. She is the author of Return to the Sea: The Life and Evolutionary Times of Marine Mammals and the editor of the award-winning Whales, Dolphins, and Porpoises: A Natural History and Species Guide.
Publisher: Princeton University Press
Published: 26th September, 2023
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