zoo's collection; this population grew rapidly and decimated the bird population at Duck Lake. A plan to shoot the squirrels was scrapped when citizens protested. Instead, as many squirrels as could be caught were sent to the Denver Mountain Parks. Mid-20th century The zoo was a motley menagerie until 1906, when Mayor Robert W. Speer declared that the zoo's "[p]rison bars can be done away with" in favor of "concrete rocks, waterfalls, trees, etc." Speer hired the city's landscape architect, Saco R. DeBoer, to draw up the plans for his renovation and appointed Victor H. Borcherdt as zoo director. Borcherdt designed the Bear Mountain exhibit, which opened in 1918. This structure is tall and long, and cost $50,000 to build ($ in dollars ). It was built of dyed and textured concrete forms cast from Dinosaur Mountain just outside Morrison, Colorado. Hidden moats replaced cage bars, and native plants and an artificial stream enhanced the natural look. The two main exhibits originally housed polar bears and grizzly bears. The south tip of the exhibit was designed to resemble Mesa Verde National Park. Originally it housed monkeys, but due to escape problems California sea lions were housed there instead. Between 1941 and 1961 it housed a female polar bear named Velox, who became the mascot of the 31st U.S. Infantry Regiment in 1952. Velox died at the zoo in 1961 and a memorial stone for her is displayed at the zoo. Bear Mountain established Denver as one of the foremost among American zoos, and the Saint Louis Zoo hired Borcherdt after seeing the exhibit. Although other zoos in the region made extensive use of New Deal funds to upgrade their facilities, only one notable addition was made to Denver Zoo between 1918 and 1950. Monkey Island was built in 1937 using funds from the Works Progress Administration. Mayor Benjamin F. Stapleton funded the zoo very little, and it was in poorly maintained condition when Mayor Quigg Newton was elected in 1947. Newton hired DeBoer, the architect involved with the zoo's design forty years before, to plan a rebirth. Starting with the 1950 overhaul of Monkey Island, the zoo has steadily added to and improved its exhibits. The Denver Zoological Foundation was created in 1950, the same year that the zoo acquired its first elephant, Cookie. A Children's zoo was opened in 1951 (since replaced by Primate Panorama). A perimeter fence was