 The Richard Friedrich Aquarium was dedicated in 1948, and the Hixon Bird House, funded through the efforts of Colonel Frederick C. Hixon, opened in 1966.The San Antonio Zoo housed the first herd of addra gazelle in captivity in 1969 and continues to be active in the breeding program for this critically endangered species.Due to the former hoofstock quarantine point in San Antonio, the San Antonio Zoo has historically had a wide variety of hoofstock species.