Cows have been fitted with GPS collars to try to stop them falling into a river.

Cambridge City Council said up to four ended up in the River Cam during grazing season between April and October each year.

Solar-powered GPS devices emit a high-pitched sound as the animal moves through a boundary zone towards the water, with a mild electric pulse delivered if it fails to turn around.

The council spends about £10,000 a year funding a team to recover cattle from the river, and said the new technology would help with costs.

Cows can be seen roaming on council-owned green spaces such as Midsummer and Stourbridge commons, Coe Fen, Lammas Land and Sheep's Green.

A team of animal rescuers employed by the council, known as pinders, are deployed if an animal gets into difficulty, such as getting stuck in the River Cam.

Last year, Cambridge City Council carried out a consultation on whether to pass the cost of the out-of-hours animal rescue service on to graziers.

However, the authority has given reassurance – after public support for cows grazing on the commons – that it will "continue to fund grazing" and has "improved animal welfare with a technology that keeps the cows from falling into the river".

Martin Smart, executive councillor for open space and city services, said: "The council recognises the symbolic importance of the cows grazing on the commons.

"This is a special and unique feature of the city that is much loved by residents and visitors alike."