We have several service dogs who are part of our community. Here are some general points of etiquette for interacting with a service animal:
1. Never pet the dog without the owner's permission.
2. Never call out to the dog while he is wearing his harness
3. Never grab the animal's harness
4. Never offer food or treats
5. Never establish eye contact with the dog while he is in harness
6. If you're with another dog, please let the handler know so the handler can advise the dog to leave it alone
Breaking any of the above rules is not only rude, but also potentially dangerous. Distracting a service animal means he will not be able to fully focus on his work, putting the handler's safety at risk. Furthermore, his social behavior could devolve if he expects a pet or a treat from every person he passes.
More information about service animal policy can be found at: http://www.ada.gov/qasrvc.htm.