Sexual dichromatism is a well-studied form of sexual dimorphism and is evident in a variety of taxa. Gibbons in the genera Nomascus and Hoolock are sexually dichromatic, with adult females having light or blonde pelage while adult males are black. All infants are born blonde, and all turn black at ca. 1–1.5 yr of age. Females then undergo a second pelage color change some time between the ages of 5 and 9 yr, when they attain their adult, blonde pelage. Here, we examine patterns of reproductive hormones (progesterone and estrone-3-glucuronide, or E1G) in 10 zoo-housed female white-cheeked gibbons (Nomascus leucogenys) during the maturation period. Females ranged in age from 2.8 to 9.8 yr during the time of sample collection. We used photographs of each female to estimate color on a five-point scale. We found a significant relationship between color and mean concentration of E1G (r = 0.69) but not between age and color (r = 0.16), or progesterone and color (r = 0.37). These results suggest a correlation between estrogen and color change in white-cheeked gibbons.

性双色性是一种经过充分研究的性双色性形式，在各种生物分类中都很明显。Nomascus和Hoolock属的长臂猿在性上是两色的，成年雌性具有浅色或金色的皮毛，而成年雄性则是黑色的。所有婴儿出生时都是金发，大约在时变成黑色。1–1.5岁。然后，当女性达到成年的金发碧眼时，女性会在5至9岁之间进行第二次肤色变化。在这里，我们研究了10个动物园饲养的雌性白颊长臂猿（Nomascus leucogenys）中的生殖激素（孕酮和雌酮3-葡萄糖醛酸，或E1G）的模式）。收集样本期间，雌性的年龄从2.8岁到9.8岁不等。我们使用每位女性的照片以五分制评估颜色。我们发现颜色与E1G的平均浓度之间存在显着的关系（r = 0.69），而年龄与颜色之间（r = 0.16）或孕酮与颜色之间没有显着关系（r = 0.37）。这些结果表明白颊长臂猿的雌激素和颜色变化之间的相关性。