Madden Derek, Young Truman P
School for Field Studies, 16 Broadway, Beverly, MA, USA.
Oecologia. 1992 Aug;91(2):235-238. doi: 10.1007/BF00317789.
We explore here the occurrence of aggressive ants in an apparently symbiotic relationship with the savanna tree Acacia drepanolobium and their effects on giraffe herbivory on the Athi-Kapiti Plains, Kenya. Trees taller than 1.3 m were more likely to be occupied by aggressive ants in the genus Crematogaster than were shorter trees. Ants wereconcentrated on shoot tips, the plant parts preferred by giraffes. Trees with relatively more foliage had more swarming ants than did trees with less foliage. The feeding behavior of individual freeranging giraffes on Acacia drepanolobium was studied. Giraffe calves exhibited a strong sensitivity to Crematogaster ants inhabiting A. drepanolobium, feeding for significantly shorter periods on trees with a greater number of aggressive ants. Older giraffes were apparently less sensitive to ants, and did not feed for shorter periods on trees with fuller foliage, despite significantly greater ant activity on these plants. The thorns of A. drepanolobium are significantly shorter than are the thorns of A. seyal, a species without symbiotic ants, a pattern that may indicate a trade-off between ants and thorns as defenses.
我们在此探究肯尼亚阿西-卡皮蒂平原上具有侵略性的蚂蚁与金合欢树之间明显的共生关系，以及它们对长颈鹿啃食行为的影响。与较矮的树相比，高于1.3米的树更有可能被举腹蚁属的侵略性蚂蚁占据。蚂蚁集中在嫩梢上，而嫩梢是长颈鹿喜欢啃食的植物部位。树叶相对较多的树比树叶较少的树有更多的蚂蚁聚集。我们研究了自由放养的长颈鹿个体对金合欢树的取食行为。长颈鹿幼崽对栖息在金合欢树上的举腹蚁表现出强烈的敏感性，在有大量侵略性蚂蚁的树上进食的时间明显较短。年龄较大的长颈鹿显然对蚂蚁不太敏感，尽管这些树上的蚂蚁活动明显更多，但它们在树叶更茂密的树上进食的时间并没有缩短。金合欢树的刺明显比没有共生蚂蚁相伴的阿拉伯胶树的刺短，这种模式可能表明在作为防御手段的蚂蚁和刺之间存在权衡。
