Unfortunately the RSPCA does not have the resources to pick up stray dogs and cats and we therefore advise you to contact your local council to attend to the matter. Some councils, however, will not collect animals unless they are contained either in box, on a lead, or if the animal is a dog, in a backyard. You may therefore be required to contain the animal. However, do not approach a dog if it is dangerous and instead call the council immediately. Be sure to notify the council if the dog has attacked any other animals and/or persons, as this is primarily a local laws matter. Alternatively, local veterinary clinics will also take stray animals and will attempt to find an owner before contacting the council.
It is a requirement of law that stray animals must enter local shelters/pounds to give owners an opportunity to find them. If you wish to keep an animal you may give your name to the local council ranger as an Interested Party, which means that in the event of no-one claiming it, you remain eligible to do so via the adoption process.
If you decide to keep the animal you must do everything within your power to find its original owner. This may include ringing local veterinary clinics, filing a report with the local council and shelters, and placing posters in local shopping centres and/or pet shops.
If the animal is injured, be especially careful if driving. Call your local shelter/council promptly as they have the equipment to deal with injured and distressed animals.