The animated short film (including the rest of materials and elements) entered the public domain in 1967, when the United Artists (UA) (a successor to the Associated Artists Productions (AAP) for pre-1948 titles) did not renew the original copyright holder, Vitaphone, within required 28-year period. - Referenced from the Looney Tunes Wiki (1, 2)
Reviewing was done by Jayvee Enaguas (HarvettFox96) on December 11, 2020. At the opening card sequence, showing a copyright notice (bottom) that reads “Copyright MCMXXXVII by The Vitaphone Corp.” Found a result for record entry there on the registration list in 1938, but not on the renewal registration list between 1965 (1, 2) and 1966 (1, 2) on copyright catalogues.
A year after it entered the public domain because the United Artists (UA) banned eleven specific short films from syndication over ethnic and racist stereotypes, which are in the group called the Censored Eleven.
The animated short film is widely available in both physical and digital formats.
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.