The phrase "stable temperament" means having a consistent and reliable way of behaving, not easily getting upset or angry.
Sentences with «stable temperament»
Active, hardy large breed with stable temperament, but very lively, with strong reactions of defence: unwanted visitors are stopped. (nextdaypets.com)
Use only physically sound, mature dogs of stable temperament for breeding. (gsdca.org)
We generally see less aggression, less territorial behavior, and a more stable temperament that doesn't fluctuate with an animal's sex hormones. (onpets.com)