From Benford's Gilbert and Sullivan Lexicon:
The first thing you should know about The Zoo is that the words are not by Gilbert; they were written by B. C. Stephenson under the pen name Bolton Rowe. The sprightly, charming music is by Sullivan. The work was first performed on June 5, 1875. (That was less than three months after the opening of Trial by Jury, but about eight years after Cox and Box.) Like Trial by Jury, it has no spoken lines. The work is brief and in a single act. After long years of neglect, it is now taking its place alongside Trial by Jury and Cox and Box as a popular curtain raiser for some of the less extensive Savoy operas.
The piano/vocal score for the work is available from R. Clyde, 6 Whitelands Ave, Chorleywood, Rickmansworth, Herts WD3 5RD, United Kingdom.
In his Note on the Libretto Terence Rees adds a few details on how one major and several minor gaps in the libretto were filled by Roderick Spencer during preparation of the published vocal score.
Present-day interest in the opera traces back to Terence Rees’s initiative in acquiring the autograph score back in 1966. Here is how he describes how it all came about:
When I was a lad, The Zoo like Thespis was very much of a mystery. It had never been published, nobody around had heard so much as a dot of the music and it received only passing mention in books dealing with the composer. And then, one day (Monday, 13th June, 1966 to be precise) the autograph full score came up for sale by auction at Sotheby’s, the famous auction house in Bond Street, London. Also up for sale were the manuscripts of Trial, Pinafore, Pirates and many others. It was a memorable event and I was there (and where were you at the time?). Intending to bid for The Zoo, I had raised all the money I could, stretching my credit right, left and centre, and expecting a fine old battle. But what I never expected was that hardly anyone in the room had heard of the piece so there was consequently little bidding. In no time at all, perhaps just two or three tense, breathless minutes, the hammer fell and I became the new owner of The Zoo.
As soon as it was all over, I paid for and collected the score, walking with it in my arms down Bond Street and along Piccadilly, past Burlington Arcade and the Royal Academy to Piccadilly Circus underground station. From there I took a train home where for the rest of that day I lay on the mat, turning the pages and wondering how I might get somebody to perform it. In the event that proved to be easier than I thought. The production at Fulham by Max Miradin was very well received, the piece caught on and has since received more performances than it ever had in Sullivan’s lifetime.