Intratree vertical variation of fruit density and the nature of contest competition in frugivores
Intratree vertical variation of fruit density and the nature of contest competition in frugivores
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DOI：
10.1007/s00265-009-0859-6
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发表时间：
2010-01-01
影响因子：
2.3
通讯作者：
Vickery, William L.
中科院分区：
文献类型：
--
作者：
Houle, Alain;Chapman, Colin A.;Vickery, William L.
最近，我们证明，最高的果肉密度位于树冠的最上部区域。由于可消耗食物的不均匀分布促进了竞争竞争，我们检验了树栖食果动物种间等级差异的三个假设：（1）在没有竞争者的情况下，种倾向于在树冠的高层取食：（2）种间竞争是通过垄断和篡夺高层的取食场所而发生的;（3）优势种进入食物斑块后，其摄食高度和摄食率下降。为了验证这些假设，我们观察了黑猩猩（Pan troglodytes），红尾猴（Cercopithecus ascanius），蓝猴（Cercopithecus mitis）和灰颊白眉猴（Lophocebus albigena）在基巴莱国家公园，乌干达。我们发现：（1）4种灵长类在单独取食时均优先选择树冠上部，（2）优势种与下位种共同取食时，优势种独占树冠上部并积极侵占树冠上部，而下位种则退缩到树冠中部以下，（3）在优势种存在时，下位种表现出较低的标准化取食高度，并改变了它们的摄食率，（4）在优势种到来时，下位种向下移动，在优势种离开时，下位种向上移动;（5）树中食叶动物的存在并不影响食果动物的取食高度，即使食叶动物是社会性的。与预期相反，我们发现，与单独进食时相比，红尾猴在蓝猴存在的情况下减少了它们在连续水果之间的运动，这可能是为了避免打扰优势种群并吸引攻击，或者是因为它们摄入了更多的半成熟和绿色未成熟的水果，即，更多低质量的食物。
Recently, we demonstrated that the highest densities of fruit pulp are located in the uppermost zones of tree crowns. Since heterogeneous distributions of depletable food is theorized to foster contest competition, we tested three hypotheses involving rank differences among species of arboreal frugivores: (1) In the absence of competitors, species tend to feed in higher strata of tree crowns; (2) interspecific contest competition occurs through monopolization and usurpation of feeding sites in these higher strata; and (3) subordinate species decrease their feeding height and ingestion rate when dominants enter the food patch. To test these hypotheses, we observed chimpanzees (Pan troglodytes), red-tailed monkeys (Cercopithecus ascanius), blue monkeys (Cercopithecus mitis), and gray-cheeked mangabeys (Lophocebus albigena) in Kibale National Park, Uganda. We found that: (1) all four primates fed preferentially in upper tree crowns when alone, (2) dominant species monopolized and aggressively usurped the upper crown when co-feeding with subordinates and the latter retreated below the middle of tree crowns, (3) in the presence of dominant species, subordinate species showed lower standardized feeding height and modified their food intake rates, while dominants were not affected by the subordinate species, (4) subordinates moved down at the arrival of and up at the departure of dominants, and (5) the presence of folivores in the tree did not affect the feeding height of a frugivore, even through folivores were socially dominant. Contrary to expectations, we found that red-tailed monkeys decreased their movements between successive fruits that they ate in the presence of blue monkeys compared to when they were feeding alone, perhaps to avoid disturbing dominants and attracting aggression or because they ingested more semi-ripe and green unripe fruits, i.e., more food of lower quality.