I have to mention Herman the US Coast Guard mouser cat who was issued with a passport during World War II. He was officially commissioned into the service in 1943. His task as stated was to control the rodent population. He was a celebrity ship’s cat as he made the news at the time. His official title was ‘Expert Mouser’.
It was all very tongue-in-cheek serious which indicates that they had some fun. Herman was a kind of mascot it seems to me and probably helped to keep up morale.
His passport details were:
Herman the Cat, occupation: EXPERT MOUSER, age: 8 months, height: 15 inches, weight: 11 pounds, eyes: GREEN, color hair: GRAY, issued on Jan. 12, 1943.US Coast Guard
His pawprint substituted a right-hand index finger fingerprint.
There have been some famous ship’s cats and they invariably achieved their fame during the war. The UK’s famous wartime ship’s cat was Simon. He was awarded the animal equivalent of the Victoria Cross (VC) Dickin Medal. The VC is the highest decoration a British soldier can achieve for valour
Some more on ship’s cats
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