The Mechanism of Replacement of Red Squirrels by Grey Squirrels: A Test of the Interference Competition Hypothesis
The Mechanism of Replacement of Red Squirrels by Grey Squirrels: A Test of the Interference Competition Hypothesis
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灰松鼠取代红松鼠的机制：干扰竞争假说的检验
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
J. Gurnell
中科院分区：
文献类型：
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作者：
L. Wauters;J. Gurnell
在英国和北方意大利的大部分地区，引进的美国灰松鼠已经取代了本地红松鼠。替代的机制尚未完全了解。我们重申了通常引用的干扰竞争假说（ICH），即灰松鼠以三种可能的方式干扰红松鼠的行为：1。通过直接的攻击性互动; 2.通过打断红松鼠的交配追逐;或3.迫使红松鼠主动避开灰松鼠密集使用的区域。我们比较了红松鼠的活动模式，行为和繁殖性能在北方意大利，一个只有红松鼠（控制区C1），其他两个物种（实验区E1）的两个研究领域。以下预测进行了测试：1。实验区红松鼠种内和种间相互作用的总时间增加; 2.大多数种间相互作用是侵略性的，以灰松鼠为优势种; 3.在E1区，繁殖雌性红松鼠断奶后代失败的比例增加; 4.灰松鼠参与并干扰红松鼠的交配追逐，从而降低红松鼠雌性的繁殖产量;在混合物种区域中红松鼠的活动模式相对于对照区域中的活动模式转移到一天中灰松鼠很少活动的时间;以及6.当灰松鼠密度增加时，红松鼠会转移它们的活动范围（或至少是它们的核心区域），以避免种间核心区域重叠。
我们的研究结果只支持ICH的第一个预测：它们不支持所有其他预测。此外，红松鼠在实验研究区域与其他松鼠互动的活跃时间百分比的增加非常小（每天仅1-2分钟）。红松鼠并没有避开灰松鼠最密集使用的林地斑块，种间核心区重叠与红松鼠种内核心区重叠相似。这表明，红松鼠避免空间重叠与灰松鼠以类似的方式与同种和灰松鼠数量的增加将增加资源竞争的强度。因此，我们的结论是，我们的研究结果并不支持干扰竞争假说和干扰竞争的灰色松鼠不能解释大规模取代红色的灰色松鼠，发生在英国和皮埃蒙特。
Introduced American grey squirrels have replaced native red squirrels in most of the range currently occupied in Britain and northern Italy. The mechanisms of the replacement are not yet fully understood. We restated the commonly cited Interference Competition Hypothesis (ICH) that grey squirrels interfere with the behaviour of red squirrels in three possible ways: 1. by direct aggressive interactions; 2. by interrupting red squirrel mating-chases; or 3. by forcing red squirrels to actively avoid areas intensively used by grey squirrels. We compared the activity pattern, behaviour and reproductive performance of red squirrels in two study areas in northern Italy, one with only red squirrels (control area C1), the other with both species (experimental area E1). The following predictions were tested: 1. the total time spent in both intraspecific and interspecific interactions by red squirrels increases in the experimental area; 2. most interspecific interactions are aggressive, with grey squirrels being the dominant species; 3. the proportion of breeding female red squirrels that are unsuccessful at weaning offspring increases in area E1; 4. grey squirrels take part and interfere with red squirrel mating-chases, and thereby decrease the reproductive output of red squirrel females; 5. the activity pattern of red squirrels in the mixed-species area is shifted with respect to that in the control area to the hours of the day during which grey squirrels show little activity; and 6. red squirrels will shift their home range (or at least their core-area) when grey squirrel densities increase to avoid interspecific core-area overlap.
Our results supported only the first prediction of the ICH: they failed to support all the other predictions. Moreover, the increase in the percentage of active time red squirrels spent interacting with other squirrels in the experimental study area was very small (only 1–2 min/day). Red squirrels did not avoid the woodland patches most intensively used by grey squirrels and the interspecific core-area overlap was similar to red squirrel intraspecific core-area overlap. This suggested that red squirrels avoided spatial overlap with grey squirrels in a similar manner as with conspecifics and that an increase in grey squirrel numbers will augment the intensity of resource competition. We therefore conclude that our results do not lend support to the Interference Competition Hypothesis and that interference competition by grey squirrels cannot explain the large-scale replacement of red by grey squirrels that has occurred in Britain and in Piedmont.