Ambush site selection and ontogenetic shifts in foraging strategy in a semi-aquatic pit viper, the Eastern cottonmouth
Ambush site selection and ontogenetic shifts in foraging strategy in a semi-aquatic pit viper, the Eastern cottonmouth
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DOI：
10.1111/j.1469-7998.2008.00527.x
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发表时间：
2009-02-01
影响因子：
2
通讯作者：
Winne, C. T.
中科院分区：
文献类型：
--
作者：
Eskew, E. A.;Willson, J. D.;Winne, C. T.
尽管对各种蛇类群的栖息地选择进行了研究，但对水生蛇物种的栖息地选择知之甚少。此外，由于幼蛇体型小，天性隐秘，它们很少被纳入栖息地选择研究。东部水腹蛇是一种半水生蝮蛇，以伏击、坐等觅食策略而闻名。伏击猎人可能会选择增加成功捕获猎物机会的栖息地，同时将捕食风险降至最低，并保持适当的热量和水分条件。研究了美国南卡罗来纳州萨凡纳河遗址上孤立的卡罗莱纳湾淡水湿地Ellenton湾水腹蛇的觅食策略和微生境利用。我们测量了51只水腹蛇在夜间视觉调查中使用的55个伏击地点的栖息地特征，以及在我们的搜索区域内随机选择的225个地点。水腹蛇在觅食策略上表现出个体发生的变化，幼水腹蛇主要在湿地边缘伏击觅食，而成年水腹蛇则经常在湿地内主动移动。主成分分析表明，幼鱼选择的觅食微生境不同于随机生境，主要由泥质基质和稀疏植被组成，而成虫占据的微生境种类更多，与随机生境没有差异。与此同时，自由放养的水腹蛇在饮食上也表现出了个体发生的变化：幼蛇主要吃蝾螈，而成年水腹蛇则吃更多种类的猎物，包括其他蛇和鸟类。我们的研究结果强调了了解蛇的颜色、饮食和捕食风险的个体发生变化如何影响觅食策略和微栖息地选择的重要性。
Although habitat selection has been studied in a variety of snake taxa, little is known about habitat selection in aquatic snake species. Additionally, due to their small size and secretive nature, juvenile snakes are seldom included in habitat selection studies. The Eastern cottonmouth Agkistrodon piscivorus is a semi-aquatic pit viper known to use ambush, sit-and-wait foraging strategies. Ambush hunters are likely to select habitats that increase opportunity for successful prey capture while minimizing predation risk and maintaining appropriate thermal and hydric conditions. We characterized the foraging strategy and microhabitat use of cottonmouths at Ellenton Bay, an isolated Carolina bay freshwater wetland on the Savannah River Site in SC, USA. We measured habitat characteristics of 55 ambush sites used by 51 individual cottonmouths located during nighttime visual surveys, as well as 225 randomly selected sites within our search area. Cottonmouths exhibited an ontogenetic shift in foraging strategy with juveniles using predominately ambush foraging around the edge of the wetland while adults were most often encountered actively moving within the wetland. Principal components analysis revealed that juveniles selected foraging microhabitats that were different from random and consisted of mud substrate with sparse vegetation, whereas adults occupied a greater variety of microhabitats that did not differ from random. Concomitantly, free-ranging cottonmouths exhibited ontogenetic shifts in diet: juveniles consumed mostly salamanders, while adults ate a greater variety of prey including other snakes and birds. Our results highlight the importance of understanding how ontogenetic changes in coloration, diet and predation risk influence foraging strategy and microhabitat selection in snakes.