FORAGING DYNAMICS OF BIRD PREDATORS ON OVERWINTERING MONARCH BUTTERFLIES IN MEXICO
FORAGING DYNAMICS OF BIRD PREDATORS ON OVERWINTERING MONARCH BUTTERFLIES IN MEXICO
复制标题
DOI：
10.1111/j.1558-5646.1985.tb00427.x
复制
发表时间：
1985-01-01
期刊：
影响因子：
3.3
通讯作者：
CALVERT, WH
中科院分区：
文献类型：
--
作者：
BROWER, LP;CALVERT, WH
通过在墨西哥一个2.25公顷的帝王蝶越冬群体内和附近悬挂渔网，估计黑背黄鹂和黑头蜡嘴每天杀死4550- 34300只蝴蝶，平均15,067只蝴蝶。在135天的越冬季节中，保守计算的死亡率为203.4万只蝴蝶或. apprx。占殖民地的9%。这些鸟有选择地捕食雄性蝴蝶，可能是因为脂肪含量的差异，也可能是因为雌性蝴蝶含有更高浓度和更大量的卡丹酮或其他防御性化学物质。在殖民地外围和森林稀疏的地区，个体帝王蝶被杀的风险要大得多。因此，鸟类捕食足以在形成帝王蝶越冬和聚集行为的演变中发挥重要作用。捕食强度的日变化很大，其中26%是由于在寒冷的日子里吃更多的蝴蝶，其中30%是由于7.85天的捕食周期。有人提出这样的假设，即鸟类周期性地进食是因为它们积累了有毒的强心甾内酯或蝴蝶中含有的其他防御性化学物质。循环捕食可使对殖民地的总捕食减少多达50%。这种基于化学物质的群体保护被解释为通过选择性过程作用于君主生活史的其他阶段而导致不适口性进化的偶然副产品。
By suspending nets within and adjacent to a 2.25 ha overwintering colony of monarch butterflies in Mexico, it was estimated that black-backed orioles and black-headed grosbeaks killed 4550-34,300 and an average of 15,067 butterlies per day. A conservative calculation of mortality through the 135 day overwintering season was 2.034 million butterflies or .apprx. 9% of the colony. The birds preyed selectively upon male butterflies, possibly because of a difference in fat content, or possibly because females contain higher concentrations and larger amounts of cardenolide or other defensive chemicals. The risk to individual monarchs of being killed was much greater on the colony periphery and in thinned areas of the forest. Bird predation thus is sufficient to have played a major role in shaping the evolution of the monarch''s overwintering and aggregation behavior. Substantial daily variation in predation intensity occurred, 26% of which was attributable to the birds eating more butterflies on colder days, and 30% of which was attributable to a 7.85 day predation cycle. The hypothesis is put forward that the birds feed cyclically because they build up toxic levels of cardenolides or other defensive chemicals contained in the butterflies. The cyclic predation may reduce total predation on the colony by as much as 50%. Such chemical-based group protection is interpreted as a fortuitous by-product of the evolution of unpalatability through selective processes acting on other phases of the monarch''s life history.