Aussies are very intelligent. They are happiest when with their families, and therefore they should not be left outside for long periods of time. They are natural watchdogs and will sound the alarm if a strange animal or person approaches.
As with other terriers, they can be dog-aggressive and somewhat bossy, and care must be taken when living in a multi-pet household. In general, adult male terriers do not get along well with other adult male dogs.