We have a 13 month old border collie, but although he is in the main a good dog, he does on occasion bite, for no apparent reason. He does sometimes give warning by showing his teeth & rolling his lips up. I am worried for the grandchildren. I would not like him to be put down.

Think you should get someone to take a look at this situation, perhaps start with having the vet check him out and make sure it is not something that is causing him to do this. Explain in detail to the vet what is happening and ask for the name of someone who can help you sort the problem. Have you spoken to his breeder, they may be able to help and they should be interested to hear about the problem you are having as it should make them consider further breeding from that line.