Here are a few http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2003/07/10/ZOO.TMP http://articles.cnn.com/2007-12-26/us/tiger.attack_1_siberian-tiger-carlos-sousa-tiger-attack?_s=PM:US http://www.boston.com/news/nation/articles/2007/12/28/tigers_escape_from_enclosure_puzzles_specialists/ http://www.huffingtonpost.com/2011/07/15/bird-escapes-denver-zoo_n_900378.html