For many households, dogs are very much part of the family, but they do not generally appear in official records. For a brief spell in the 18th century, however, a tax was levied on dog owners (this tax was on non-working dogs). The tax records for Scotland are available on the ScotlandsPlaces website (which is a free website), so you can easily search them to find out if your family had a (non-working) dog.
The Dog Tax rolls 1797-1798 are in two volumes, arranged by county with each parish being listed within that county. Let us know if you find a entry relating to your family.