Barthold Julia, Fichtel Claudia, Kappeler Peter
Department of Sociobiology and Anthropology, University of Göttingen, Göttingen, Germany.
Am J Phys Anthropol. 2009 Jan;138(1):1-10. doi: 10.1002/ajpa.20868.
In some primate species, pelage colorations at birth contrast with adult colorations. The intensity of natal coats and their phylogenetic distribution is highly variable within primates. Natal coat coloration seems to change to adult coloration in most species when infants become independent from their mothers, but an accepted functional explanation for natal coats is not available. Here we describe pelage coloration change in sexually dichromatic redfronted lemurs (Eulemur fulvus rufus) in Kirindy Forest, and propose a new functional hypothesis for this phenomenon. In this species, infants are born with adult male coloration and female infants subsequently undergo a change in coloration. Using digital pictures and behavioral data collected on eight mother-offspring dyads from birth until the end of the coloration change, we 1) described timing and pattern of pelage developmentin redfronted lemur infants and 2) examined behavioral developmental correlates of the coloration change. The color change took place between 7 and 17 weeks of age and coincided with advanced physical independence; a pattern also found in monochromatic primate species with natal coats. No behavioral differences between male and female infants were found. Hypotheses about the ultimate function of natal coats focusing on enhanced infant care or reduced infanticide risk did not explain the pelage change in redfronted lemurs. The natal pelage pattern in this species may instead serve as sexual mimicry. Accordingly, female infants may mimic males during the most vulnerable developmental phase to avoid sex-specific aggression by adult females in a species with intense female-female aggression and competition.
在一些灵长类物种中，出生时的皮毛颜色与成年时的颜色形成对比。出生时皮毛的颜色强度及其系统发育分布在灵长类动物中高度可变。在大多数物种中，当幼崽从母亲身边独立出来时，出生时的皮毛颜色似乎会变成成年时的颜色，但目前还没有关于出生时皮毛颜色的公认功能解释。在这里，我们描述了基林迪森林中具有性别二态性的红额狐猴（Eulemur fulvus rufus）的皮毛颜色变化，并为这一现象提出了一个新的功能假说。在这个物种中，幼崽出生时具有成年雄性的颜色，随后雌性幼崽的颜色会发生变化。我们使用从出生到颜色变化结束时收集的关于八个母婴二元组的数码照片和行为数据，1）描述了红额狐猴幼崽皮毛发育的时间和模式，2）研究了颜色变化与行为发育的相关性。颜色变化发生在7至17周龄之间，与身体进一步独立的时间一致；在具有出生时皮毛的单色灵长类物种中也发现了这种模式。未发现雄性和雌性幼崽之间存在行为差异。关于出生时皮毛颜色的最终功能的假说，即侧重于加强幼崽照顾或降低杀婴风险的假说，无法解释红额狐猴的皮毛变化。相反，这个物种出生时的皮毛模式可能起到性模仿的作用。因此，在一个存在强烈雌性间攻击和竞争的物种中，雌性幼崽可能在最脆弱的发育阶段模仿雄性，以避免成年雌性的性别特异性攻击。
