Today is International Gibbon Day! The Phoenix Zoo is home to two buff-cheeked gibbon siblings. Enik is an 18-year-old male black buff-cheeked gibbon, and China is a 20-year-old female yellow buff-cheeked gibbon. Fun fact, they share the same birthday, September 12th, but were born two years apart! Buff-cheeked gibbons exhibit sexual dichromatism (adult males are black with only yellow cheeks, and females are all yellow). At birth, buff-cheeked gibbons are a bright yellow color, but during the s