The Pen Is Milder Than the Blade: Identification Marking Mice Using Ink on the Tail Appears More Humane Than Ear-Punching Even with Local Anaesthetic.

Identification marking mice commonly involves ear-punching with or without anaesthetic, or tail-marking with ink. To identify which is most humane, we marked weanling male BALB/c mice using ear-punching (EP), ear-punching with anaesthetic EMLA cream (EP+A), or permanent marker pen (MP). We compared marked mice, unmarked cagemates, and control mice ( = 12-13/group) for 5 weeks, reapplying MP weekly.