The   San Diego Zoo   is located in Balboa Park.   Began with a collection of animals left over from the 1915 Panama-California Exposition, but officially in 1921. Frank Buck became director in 1923, but left after three months, and returned to animal collecting.  Belle Benchley became executive secretary, then zoo director from 1925 to 1953, quite a feat, for she was around the only female in this leading role throughout the world Zoo began as a pioneer, featuring open-air and cageless animals in their natural habitat. Sits on 100 acres, with more than 700,000 exotic plants, now housing 12,000 animals of more than 680 species.  In comparison, the Honolulu Zoo has 1230 animals and more than 900 species.  40 varieties of bamboo for their pandas, and 18 of eucalyptus trees to feed its pandas. There are now two pandas on exhibit.   Read about this history,  for in the past several pandas were born here, and sent back to China. There are fiv...