The device (10) has ear bars (14) including arms (140) mounted swiveling on a frame and ends (142) arranged to cooperate with an ear of an animal, and placed on a portion of a distal end of the arm. An adjustment unit co-operates with the arms to regulate spacing of the ends. The adjustment unit includes a rotary wheel (16) to co-operate in abutment with the arms. Actuation of the wheel along a rotation direction (R1) forces the arms to swivel in a swiveling direction (T1) while actuation of the wheel in another rotation direction (R2) releases the arms in another swiveling direction (T2).