Sound is as important to whales as vision is to us. Sound travels farther in the ocean than light does — so whales and dolphins grunt, call, click or sing, or listen intently, and their lives depend on sending and receiving these acoustic cues reliably. They’re quite good at it. Whales and their prey have evolved these acoustic systems over millennia. The problem is that in the last hundred years or so, we have started competing with whales for acoustic space by using ships and conducting other activities that create a lot of underwater noise (mostly unintentionally). So a whale singing in a noisy habitat is like having a great cell phone that relies on a terrible network provider. Unfortunately for whales, fish, squid and other marine life, the consequences of a “dropped call” are more serious than they are for us. If human activities jam whale acoustic signals, the information lost is not trivial. We suspect that the acoustic information being transmitted is of the kind: “There is a predator just around the corner.” Or, “Eat this fish. It may be the last one you see for days.” Or, “Mate with me.” You don’t want to miss these calls.
Killer whales depend on a quiet ocean to navigate, find food and choose mates. Much of our work with acousticians at Cornell involves estimating how much acoustic habitat whales are losing from chronic, rising levels of noise. Here’s a simple animation that describes that work.
In addition to masking the whales’ calls, animals can also show behavioural responses to ships. Our new research, published in Marine Pollution Bulletin, shows that ships cause whales to change their swimming speed, breathing patterns and path direction. In most parts of the whales’ range, whales rarely encounter big ships; but in the whales’ most important, critical habitats (Johnstone and Haro Straits), the whales may encounter a big ship every hour of every day.
This new research allows us to predict how often the whales change their behaviour to accommodate a ship. Our next work will make some predictions about what it might cost the whales at a population level to spend less time feeding and more time avoiding ships. Our ultimate aim is to partner with ship builders and operators to find ways to reduce those costs to whales.