Tales of the Riverbank, usually referred to as Hammy Hamster, was a British children's television show by the BBC. First aired in 1960, in 13 black and white episodes. But the stand-out episodes for most people are the colour versions which were actually named Hammy Hamster's Adventures On the Riverbank (1972), and voiced by Johnny Morris. But were shown on ITV as the BBC had developed a weird policy of not using human voices for live animals!
The characters included Hammy Hamster (my first hamster was called after him), Roderick the Water Rat, G.P. the Guinea Pig, among many others. As they were real live animals, the producers at the Isle of Wight studios where the series were made, released the animals into the wild at end of filming in 1973. The rats, hamsters and other animals died not long after release, but the Mongolian Gerbils survived for at least three years, the colony reaching around 100.