Researchers monitoring of pod of orcas in the waters off Washington (US) found that speed was a more influential factor than how big a boat was when it came to the amount of noise from vessels reaching the pod.
Previous studies have shown that Southern Resident orcas alter their behaviour in the presence of ships and related noise.
Whales and dolphins live in a world of sound. They communicate, find their way around and locate food using sound. Noise pollution threatens whale and dolphin populations, interrupting their normal behaviour, driving them away from areas important to their survival, and at worst injuring or even causing death.
This most recent research has also found that it is likely that the orcas have to use extra energy to call more loudly when boats are operating nearby. Previous studies have identified vessel traffic and noise as two main threats to recovery of the endangered population of this resident pod, which now only numbers about 80 orcas.