Most of our breeds of dogs today, descend from hunting dogs.
Towns use to employ a man called a rat catcher, whose job it was to kill rats, but towns still had rats, and the rats spread disease, so...
In order to encourage the public to help get rid of the rats that were spreading disease, the government made rat killing a sport. People would bet on how many rats a dog could kill in a set amount of time.
To supply the rat pits, people had to catch rats (There were no wire cages then, so they could not cheat by raising rats).
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The plague was spread by fleas including fleas that lived on rats.
It is estimated that 1 out of every 4 people in Europe was killed by the plague.
Governments did their best to stop rats from breeding - picking up the garbage and burying or burning it helps keep down rat numbers, as the rats have less to eat.
Somebody even dreamed up a tale of a great way to get rid of rats - The Pied Piper. He played a song so sweet that the rats fell into a trance and then the Pied Piper led them out into the sea, where he, still playing music on his pipe, got into his boat. The rats followed the music and drowned.
Good story but rats don't follow music and they DO swim very well.
Watch this video on MODERN 'rat' pit 'killing', how many 'rats' does the terrier kill?
Photos links:
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