University of Georgia, Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29802, USA.
Ecology. 2011 Mar;92(3):744-54. doi: 10.1890/10-0781.1.
Resource availability and accessibility are primary factors guiding the distribution and abundance of organisms. For generalists, prey availability reflects both prey abundance and differences in quality among prey taxa. Although some aspects of prey quality, such as nutritional composition, are well studied, our understanding of how prey morphology contributes to overall prey quality is limited. Because snakes cannot reduce prey size by mastication, many aspects of their feeding ecology (e.g., maximum prey size, feeding performance, and the degree of postprandial locomotor impairment) may be affected by prey shape. We conducted a uniquely comprehensive comparison of prey quality for a generalist species, the banded watersnake (Nerodia fasciata), using prey that were similar in mass and presumably similar in nutritional composition but different in shape and habitat association. Specifically, we compared nutritional composition and shape of paedomorphic salamanders (Ambystoma talpoideum) and sunfish (Lepomis MARGINATUS) and used a series of repeated-measures experiments to examine feeding performance (number of prey consumed, maximum prey size, and intra-oral transport time), digestive metabolism (specific dynamic action, SDA), and postprandial locomotor performance of snakes fed Ambystoma and Lepomis. Cost of digestion was similar between the prey types, likely reflecting their similar nutritional composition. However, snakes consumed larger Ambystoma than Lepomis and intra-oral transport time was much shorter for Ambystoma. Snakes fed Lepomis also suffered greater reduction in crawling speed than those fed Ambystoma. These differences highlight the need for behaviorally integrated approaches to understanding prey quality and support field observations of the importance of amphibian prey for juvenile watersnakes.
资源的可利用性和可及性是指导生物分布和丰度的主要因素。对于广食性动物来说，猎物的可利用性反映了猎物的丰富度和猎物分类群之间的质量差异。虽然猎物质量的某些方面，如营养成分，已经得到了很好的研究，但我们对猎物形态如何有助于整体猎物质量的理解是有限的。由于蛇不能通过咀嚼来减小猎物的大小，它们的许多进食生态学方面（例如，最大猎物大小、进食表现和进食后运动能力的受损程度）可能会受到猎物形状的影响。我们对一种广食性物种——带状水蛇（Nerodia fasciata）的猎物质量进行了一次独特的全面比较，使用的猎物在质量上相似，而且据推测在营养成分上也相似，但形状和栖息地的关联却不同。具体来说，我们比较了幼态变形蝾螈（Ambystoma talpoideum）和太阳鱼（Lepomis MARGINATUS）的营养成分和形状，并使用一系列重复测量实验来研究蛇类的进食表现（消耗的猎物数量、最大猎物大小和口腔内运输时间）、消化代谢（特定动态作用，SDA）和进食后运动表现。两种猎物类型的消化成本相似，这可能反映了它们相似的营养成分。然而，蛇类消耗的幼态变形蝾螈比太阳鱼多，而且幼态变形蝾螈的口腔内运输时间也短得多。喂食太阳鱼的蛇类的爬行速度比喂食幼态变形蝾螈的蛇类下降得更厉害。这些差异突出了需要采用行为综合的方法来理解猎物质量，并支持了野外观察到的两栖类猎物对幼年水蛇的重要性。
