A dog owner is warning others to be wary after his pet ate cannabis during a walk along a beach. Stephen Davidson was hit with a hefty vet’s bill after his West Highland white terrier swallowed the drug in Sheerness on Saturday. The 59-year-old told how an hour after the walk, Oscar started acting strangely as if he was “away with the fairies”. The eight-year-old pet who is usually “clingy and lovable” had become almost lifeless and stopped drinking. A concerned Stephen phoned an out-of-hours vet fearing his family dog “could have dehydrated and died”. Shortly afterward, he rushed him to the P…