A person whose vehicle strikes, kills, injures, or damages an unattended animal running at large on a highway is not liable for damages to the animal except as a finding of:

1. (1) gross negligence in the operation of the vehicle; or
2. (2) wilful intent to strike, kill, injure, or damage the animal.

Acts 1981, 67th Leg., p. 1350, ch. 388, Sec. 1, eff. Sept. 1, 1981.