It’s hard to believe the Palm Beach Zoo is turning 50. That’s five decades of koala close-ups, sloth encounters, and flamingling. In its lifetime, the zoo has gone from a small operation with a handful of barnyard animals to a 23-acre attraction and conservation facility housing more than 500 creatures, such as a rare white alligator, Malayan tigers, and a formidable jaguar exhibit, among others. Last year’s visitor count topped 340,000. The coming season will bring a host of celebratory events, including a golden anniversary gala on February 1.