We claim the ornamental design for an animal ear tag, as shown and described.
FIG. 1 is a top, front, left perspective view of an animal ear tag according to our design;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is a right view thereof;
FIG. 5 is a left view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken lines depict unclaimed features of the animal ear tag that are shown for purposes of illustration and that form no part of the design claim.