Last updated January 11, 2018 at 10:42 am
Porpoises hunt their prey with astounding precision using echolocation, but until now scientists have not known how they detect their small prey with such accuracy, and at such long distances.
New research suggests that porpoises can fine-tune their sonar by slightly changing the shape of their heads, controlling the interfaces of bone, air, and tissue. This insight will help the development of advanced ultrasound imaging devices and other ultrasonic imaging applications.
Echolocation is a sensing technique used by bats, toothed whales (porpoises), shrews, and even some birds. But the system is at its most precise and powerful in the toothed whales, since in the ocean vision is highly limited and sound travels much further than in air.
Echolocation works much as the word suggests: the creature emits a sound, and by listening for the echo, it creates a mental map of its environment.
Porpoises have a specialised organ for emitting their echolocation clicks, called a melon. This large bulb of fatty tissue is the key to their fantastic abilities.
The shape of the melon helps porpoises steer and focus the echolocation click.
When waves pass from one material to another, they tend to change direction. In the case of light, this phenomenon makes eye glasses and other lenses possible and it is why sunset is orange, as red light is bent at a different angle to blue light as it enters earth’s atmosphere.
The more different the materials are, the more the waves direction changes. And that is the key to how the porpoises’ melons work with sound waves. By controlling the shape and position of the fatty tissue of the melon and air sacs relative to the bones in their heads, porpoises have amazing control over the direction of their echolocation.
Combinations of materials to produce an effect that no single material could produce are called metamaterials. It is a relatively new idea in science, but porpoises have been doing this for more than 30 million years.
This research shedding light on their abilities will help the development of new metamaterials that will help to improve and miniaturise ultrasound imaging devices.
The research was published in the journal Physical Review Applied.