Palombit R A
Animal Behavior Group, University of California, Davis, USA.
Folia Primatol (Basel). 1997;68(6):321-37. doi: 10.1159/000157260.
Studies of the siamang (Hylobates syndactylus continentis) and the lar gibbon (Hylobates lar lar) where they co-occur in mainland Asia have demonstrated interspecific dietary segregation based on body size and have suggested that observed levels of frugivory represent metabolically based maxima for these species. I studied sympatric groups of siamang (H. s. syndactylus) and lar gibbons (H. l. vestitus) at Ketambe in northern Sumatra (Indonesia) in order to assess the magnitude of within- and between-species variation in diets. The insular subspecies are considerably more frugivorous (60-70% of feeding time) than mainland conspecifics (35-50%). This is primarily because Sumatran hylobatids spend about twice as much time (approx. 45% of feeding) eating fig fruits (Ficus spp., Moraceae). A higher density of figs at Ketambe (compared to Kuala Lompat) may account for this behavioral difference. Enhanced frugivory has been achieved at the expense of folivory, which is much reduced in Sumatra--especially in H. lar (4% of diet)- and is limited almost entirely to immature foliage. The expected decline in protein intake resulting from diminished folivory in Sumatra may be counterbalanced by observed increases in insectivory, which is especially pronounced in lar gibbons. Interspecific dietary segregation emerges most clearly in how individuals of each species supplement their similarly fig-dominated diets. Siamang rely more on immature foliage--primarily from lianas, which generate young leaves more reliably and abundantly than trees do. Conversely, lar gibbons exploit the pulpy fruit of trees and lianas more heavily than siamang do. This general pattern occurs where the two species coexist in Malaysia, thereby suggesting a substantive interspecific difference that is somewhat greater in the insular populations.
对合趾猿（Hylobates syndactylus continentis）和白掌长臂猿（Hylobates lar lar）在亚洲大陆同域分布地区的研究表明，它们基于体型大小存在种间饮食分化，并且指出观察到的食果水平代表了这些物种基于代谢的最大值。我对印度尼西亚苏门答腊岛北部克塔姆贝的合趾猿（H. s. syndactylus）和白掌长臂猿（H. l. vestitus）同域群体进行了研究，以评估种内和种间饮食差异的程度。与大陆同类相比，岛屿亚种的食果性更强（取食时间的60 - 70%）（大陆同类为35 - 50%）。这主要是因为苏门答腊的长臂猿类花费大约两倍的时间（约取食时间的45%）食用榕属果实（桑科榕属植物）。克塔姆贝（与瓜拉隆帕相比）更高密度的榕树可能解释了这种行为差异。食果性增强是以减少食叶性为代价的，在苏门答腊，食叶性大幅减少——尤其是在白掌长臂猿中（占饮食的4%），并且几乎完全限于未成熟的树叶。苏门答腊食叶性减少导致的蛋白质摄入量预期下降，可能会被观察到的食虫性增加所抵消，食虫性在白掌长臂猿中尤为明显。种间饮食分化在每个物种的个体如何补充其同样以榕树为主的饮食方面最为明显。合趾猿更多地依赖未成熟树叶——主要来自藤本植物，藤本植物比树木更可靠、更大量地产生嫩叶。相反，白掌长臂猿比合趾猿更大量地利用树木和藤本植物的肉质果实。这种总体模式在这两个物种在马来西亚共存的地方出现，从而表明种间存在实质性差异，在岛屿种群中这种差异更大一些。
