A marker capsule for a drug delivery dart that marks a animal upon impact to indicate it has had a drug injection. The marker capsule is formed of a rupturable material, and has a central aperture formed therethrough for disposition about a cannula extending from the drug delivery dart. A marking substance is contained within the capsule. The capsule ruptures between the dart body and the animal upon impact to thereby disperse said marking substance upon the animal about the area of the impact.