The astonishing death rate of Japanese pets has been attributed by animal welfare groups to rapidly changing trends in the ownership of certain pets, which are no longer wanted once they go out of fashion.
Recent favourites have included golden retrievers and labradors, which are the currently fad, and Siberian huskies. The breeds are unsuitable for the typically confined apartments found in most Japanese cities and are often kept outside.
Landlords are exceptionally strict on the keeping of animals and many pet-owners are forced to give up their animals when they move.
In all, 307,000 cats and 235,000 dogs were put down in Japan last year.
Action is hardly ever taken against the owners. In 1996, only one prosecution for cruelty was brought in the whole of Japan.
The scale of the animal slaughter is put into further perspective when compared to the death rates of domestic pets in other countries. In Britain, 17,000 stray dogs were put down last year.
A team from BBC Radio's Asia File recently visited some of the dog and cat pounds in Japan and were horrified by the conditions the animals were kept in before being put down.
One terrier was delivered to the pound by its owner with parcel tape around its jaws, and a notice around its neck saying: "This dog bites". No action was taken against the owner.
In Osaka, single cages contain up to 38 dogs, which are exterminated within three days of arrival. Hugh Levinson, the programme's producer, said: "These dogs were going absolutely nuts, jumping on top of each other. Some had their fur ripped off and blood on their muzzles."
He added: "It's not that the Japanese don't like animals; they are very sentimental about them. But it's a very romanticised, anthropomorphic idea and has nothing to do with the fact that dogs need walking and they bite and they tend to make a lot of mess."
The large numbers of unwanted pets are made worse by the fact that cats and dogs in Japan are rarely neutered.
Elizabeth Oliver, a British animal lover who has set up the Ark animal refuge in Japan, said Japanese people traditionally have not kept dogs but they became fashionable in the 1980s.
"They looked around for what the popular dog was and then these booms started. There used to be the sheltie boom, then the beagle boom then the husky boom and currently it's the golden retriever boom, which is just on the wane, and it's going into labradors, cavalier spaniels," she said. "They change - out with this year's fashion and in with next year's."
Hideo Yamazaki, of the Japanese prime minister's office, said: "Our laws on animal protection and management generally have the aim of aiding the welfare of animals ...
"It doesn't follow that because the number of prosecutions is low, there is a lot of cruelty towards animals in Japan or that the Japanese don't care for animals."
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