Dolphins will be replaced by robots in 2017

It has been announced that the naval programme of training sea mammals to tag mines, which begun in the 1950s, is set to be phased out in favour of using machines.

This new alteration will begin in five years' time, when 24 of the Navy's military-trained dolphins will be replaced by a 3.6 metre (12ft) unmanned torpedo-shaped vehicle.

The US Navy plans to reassign the mine-tracking dolphins rather than make them redundant. It has been reported they will be used along with sea lions for port security and retrieving objects from the sea floor.

The military has assured that, unlike the seven years it takes to train a dolphin, the machines can do some of the same mine-hunting duties and can be quickly manufactured.

The Navy's $28m (£17.4m) marine-mammal program dates back to the late 1950s, when it once included killer whales and sharks. Based in San Diego, it currently uses 80 bottle-nosed dolphins and 40 California sea lions.

In recent years, dolphins have been deployed to Iraq and Bahrain to patrol for enemy divers and mark the locations of mines.

Using their innate sonar, the mammals find and mark mines in shallow water, in deep water when tethers are used, and on the bottom where sediment cover and plant growth can hide the devices.

The military is responsible for the mammals' care throughout their lives, even after they're retired from active duty. Sometimes Navy dolphins are loaned to animal parks, such as Sea World, later in life.