alert animal black dog groningen guard guard-dog pet shape sign vector warning white animals bark best boerboel Ears friend gay mastiff nose portrait watch advice advising be-careful beware canine canine-guard communicate communication danger information informing lettering letters lookout mammal message no-entry observe risk risky security warned watch-out wording words afraid doggy gaze grass interested Look nature protect puppy shock spot walk breed cute eye lovely play protector rest rural sit watching york bite dangerous face farm guardian hunting resting sheepdog