Roger Pinney BBC Wales' environment correspondent

There are over 120 dolphins living in Cardigan Bay

And that's hardly surprising. They are stunningly beautiful creatures. Who could resist it after all?

You only have to watch them leap or surf after boats. They are delightful, fun creatures, aren't they?

Well no - they are wild animals. Ferocious predators at the top of the ocean food chain.

As one naturalist put it to me: "Swim with dolphins? Forget it. Your wouldn't ask me to cuddle a lion, would you?"

Now off the west Wales coast, there's increasing evidence that they are responsible for the deaths of their smaller cousin, the porpoise.

So far this year more than eighty porpoises have washed up on Welsh beaches.

Porpoises are much more elusive than dolphins

The vast majority died from disease, lack of food or after getting caught in fishing nets.

But a worrying number show tell-tale signs of dolphin attack.

The west Wales coast is renowned by naturalists across the world for the richness of its wildlife.

Seabirds such as puffins, Manx shearwaters and gannets are in abundance.

The sea is home to dolphins and porpoises and whales. But it is also a killing ground.

Competition

It's Rod Penrose's job to investigate marine mammal strandings. He collects porpoises, dolphins and whales which wash up on the shoreline.

If the dead animal is in good enough condition he takes it to London Zoo for a post-mortem examination.

Now he's finding an increasing number of porpoises which have been killed by bottlenosed dolphins.

In Britain the phenomenon was first recorded off Scotland's Moray Firth about ten years ago.

It appears to have been taken up by the Cardigan Bay dolphin population.

Secretive

Quite why is still guesswork. Rod Penrose's own theory is that it is competition for food.

He believes porpoises need further study. Unlike the dolphins they are mostly shy, secretive creatures which avoid contact with humans.

No-one even knows how many of them live off the Welsh Coast.

It's their boastful gregarious cousin the dolphin which always steals the show.... and the attention of conservationists.

Anyone finding a stranded porpoise, dolphin or whale on the Welsh Coast should report it to the National Strandings Line: 01348 875000.