Ive also found temperament to be genetic ...

Biters produce biters, hoarders produce hoarders, etc.

I have 3 criteria (these go by priority) ... one is larger than litter mates, larger than average litter size, and temperament.

The first animals that I usually cull are undersized/dwarfs and then whites, unless they fall into the first 2 categories, For some reason I just dont like white rats or mice.

Bryan