Data from: Foraging mode, relative prey size and diet breadth: a phylogenetically-explicit analysis of snake feeding ecology

1. Foraging modes (ambush vs. active foraging) are often correlated with a suite of morphological, physiological, behavioral and ecological traits known as the adaptive syndrome or syndrome hypothesis. In snakes, an ecological correlate often reported in the literature is that ambush-hunting snakes have a higher relative meal size compared to actively foraging snakes which feed on smaller prey items. This "large meal vs. small meal" feeding hypothesis between ambush and active foragers has become a widely-accepted paradigm of snake feeding ecology, despite the fact that no rigorous meta-analysis has been conducted to support this generalization. 2. We conducted a phylogenetically-explicit meta-analysis, which included ca. 100 species, to test this paradigm of snake feeding ecology. 3. We gathered data on prey size by inducing regurgitation by palpation in free-ranging snakes and by examining the stomach contents of preserved museum specimens. When we found prey, we recorded both snake and prey mass to estimate relative prey mass (prey mass/snake mass). We also reviewed published studies of snake feeding ecology to gather similar information for other species. 4. Ambush and active foragers did not differ in minimum or average meal size but the maximum meal sizes consumed by ambush-foraging snakes were larger than the maximum meal sizes eaten by active foragers. This results in ambush-foraging snakes consuming a significantly wider range of meals sizes, rather than being large meal specialists compared to active foragers. We argue that ambush foragers evolved to be more opportunistic predators because they encounter prey less frequently compared to active foragers. This hypothesis is further supported by the fact that ambush foragers also exhibited marginally wider diet breadths, consuming a broader range of prey types in comparison to active foragers. 5. Our study challenges aspects of the foraging syndrome as it is currently conceived, and our results have important implications for our understanding of how foraging mode has shaped the behavior and physiology of ambush-foraging snakes.

1. 伏击觅食（ambush foraging）与主动觅食（active foraging）两种觅食模式，通常与一套被称为适应综合征（adaptive syndrome）的形态、生理、行为及生态特征相关联，即综合征假说。在蛇类研究中，学界常报道的生态关联为：伏击觅食蛇类的相对摄食量，显著高于以小型猎物为食的主动觅食蛇类。尽管尚无严谨的元分析（meta-analysis）支撑这一泛化结论，但二者间“大食量vs小食量”的摄食假说，已成为蛇类摄食生态学领域被广泛接受的研究范式。
2. 本研究开展了一项包含约100个物种的系统发育显式元分析（phylogenetically-explicit meta-analysis），以检验这一蛇类摄食生态学范式。
3. 研究通过对野外自由活动的蛇类触诊诱导呕吐，以及检视馆藏博物馆标本的胃容物，收集猎物大小相关数据。当检出猎物时，同步记录蛇体与猎物的质量，以此计算相对猎物质量（猎物质量/蛇体质量）。同时，本研究还梳理已发表的蛇类摄食生态学研究，为其余物种收集同类数据。
4. 结果显示，伏击与主动觅食者的最小或平均摄食量并无显著差异，但伏击觅食蛇类的最大摄食量显著高于主动觅食蛇类。这表明伏击觅食蛇类的摄食量范围显著更广，相较于主动觅食者，它们并非仅以大型猎物为食的特化捕食者。我们提出，相较于主动觅食者，伏击觅食者因遭遇猎物的频率更低，因此演化出更具机会主义特征的捕食策略。这一假说进一步得到佐证：伏击觅食者的食谱宽度也略微更广，相较于主动觅食者，其可捕食的猎物类型范围更宽泛。
5. 本研究对当前学界所认知的觅食综合征的部分内容提出了挑战，其研究结果对我们理解觅食模式如何塑造伏击觅食蛇类的行为与生理特征具有重要意义。