Some whales show damage suggesting they surfaced too quickly, experts say
Increasing noise pollution in the world's oceans is threatening the survival of whales and dolphins, a UN-backed conference has heard.
Experts say the noises sea creatures use to communicate are being drowned out by noises from commercial shipping, new military sonar and climate change.
They become disoriented, cannot find mates or food and behave differently, scientists say.
Suggestions to cut noise include installing quieter engines.
The Convention on the Conservation of Migratory Species of Wild Animals, which representatives from 100 countries are attending, is considering issuing a resolution that would oblige countries to reduce sound pollution.
Other suggested measures include re-routing shipping, cutting speed and banning tests and sonar use in the habitats of endangered animals.
Describing the increasing noise in oceans, Mark Simmonds from the Whale and Dolphin Conservation Society said: "Call it a cocktail-party effect: you have to speak louder and louder until no-one can hear each other anymore."
He said there were a growing number of cases where the stranding of whales and dolphin could be linked to sound pollution.
In some cases, the mammals had tissue damage similar to divers who surface too quickly, leading scientists to suggest that they were scared by military sonar or seismic testing, and surfaced beyond their physical limits, he added.
Other research suggests that rising levels of carbon dioxide are increasing the acidity of the Earth's oceans, making sound travel further through sea water.