Mixed fortunes for world's whales

The latest global assessment of cetaceans shows that the marine mammals throughout the world's oceans have experienced mixed fortunes.

The IUCN Red List of Threatened Species reveals that some large species, like humpbacks, have seen numbers increase.

However, it warns that smaller species, including river dolphins, have declined as a result of human actions.

The IUCN added that it was unable to assess more than half of the world's cetaceans because of a lack of data.

"It shows that if you protect these animals then they can recover," said Randall Reeves, chairman of Cetacean Specialist Group for the IUCN, the global conservation body.

"I'm encouraged by the fact that several of the large whale species that had been in trouble for a long time have shown steady increases over recent decades."