In 1965, famed oceanographer Jacques Cousteau co-directed a documentary called The Silent World, but as Kathy Heise, research associate at the Vancouver Aquarium Marine Science Centre, points out – the ocean is not so silent after all. There are sounds made by human activities, sounds made by animals and sounds made by whales and dolphins, some at such a high frequencies that humans can’t hear them.
It’s this kind of sound – echolocation – that Kathy is studying onsite at the Aquarium. Echolocation works like sonar. Dolphins direct sounds through a fatty organ (melon) in their heads. Then, they listen for those sounds to bounce off of objects, like an echo. The echo travels back through their fat-filled lower jaws and into their inner ears, allowing them to create a mental picture of their surroundings.
Kathy want to know why – despite having “terrific” echolocation capabilities – do dolphins become entangled in fishing nets? She asks, “Are there characteristics of echolocation that stop them from seeing the net?”
To find out, she has enlisted the help of the dolphin trainers and the two Pacific white-sided dolphins at the Vancouver Aquarium. Both Helen and Hana were rescued and rehabilitated after having been entangled in nets themselves. The trainers are training the dolphins to react when they detect a net using echolocation. The research will test for different types of nets at various distances.
According to the WWF, 300,000 dolphins, whales and porpoises entangle and drown in fishing nets each year. Understanding why this happens may one day lead to better fishery methods and management practices that will help conserve these marine mammals.
Kathy has discovered in her many years as a dolphin researcher, both in the wild and at the Aquarium, that every individual is different and that there isn’t a single way to understand all dolphins. Indeed, Helen and Hana have already taught her so many different things about their noisy underwater world.
Learn more about dolphin research at the Vancouver Aquarium.
Written by Karen Horak, writer-editor, content and digital experience at the Vancouver Aquarium.