Díaz José A, Carrascal Luis M
Departmento de Biología Animal I (Vertebrados), Facultad de Biología, Universidad Complutense, 28040, Madrid, Spain.
Departmento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales, CSIC, Jose Gutiérrez Abascal 2, 28006, Madrid, Spain.
Oecologia. 1993 May;94(1):23-29. doi: 10.1007/BF00317296.
Maximizing the average rate of energy intake (profitability) may not always be the optimal foraging strategy for ectotherms with relatively low energy requirements. To test this hypothesis, we studied the feeding behaviour of captive insectivorous lizards Psammodromus algirus, and we obtained experimental estimates of prey mass, handling time, profitability, and attack distance for several types of prey. Handling time increased linearly with prey mass and differed significantly among prey types when prey size differences were controlled for, and mean profitabilities differed among prey taxa, but profitability was independent of prey size. The attack distance increased with prey length and with the mobility of prey, but it was unrelated to profitability. Thus, lizards did not seem to take account of the rate of energy intake per second as a proximate cue eliciting predatory behavior. This information was combined with pitfall-trap censuses of prey (in late April, mid-June and late July) that allowed us to compare the mass of the prey captured in the environment with that of the arthropods found in the stomachs of sacrificed free-living lizards. In April, when food abundance was low and lizards were reproducing, profitability had a pronounced effect on size selection and lizards selected prey larger than average from all taxa except the least profitable ones. As the active season progressed, and with a higher availability of food, the number of prey per stomach decreased and their mean ize increased. The effect of profitability on size selection decreased (June) and eventually vanished (July-August). This variation is probably related to seasonal changes in the ecology of lizards, e.g. time minimization in the breeding season as a means of saving time for nonforaging activities versus movement minimization by selecting fewer (but larger) prey in the postbreeding season. Thus, the hypothesis that maximizing profitability could be just an optional strategy for a terrestrial ectothermic vertebrate was supported by our data.
对于能量需求相对较低的变温动物而言，将平均能量摄入率（盈利能力）最大化并不总是最优的觅食策略。为了验证这一假设，我们研究了圈养食虫蜥蜴阿尔及利亚沙蜥的摄食行为，并获得了几种猎物的猎物质量、处理时间、盈利能力和攻击距离的实验估计值。处理时间随猎物质量呈线性增加，在控制猎物大小差异后，不同猎物类型之间存在显著差异，不同猎物类群的平均盈利能力也不同，但盈利能力与猎物大小无关。攻击距离随猎物长度和猎物的活动能力增加，但与盈利能力无关。因此，蜥蜴似乎没有将每秒的能量摄入率作为引发捕食行为的直接线索。这些信息与猎物的陷阱诱捕普查（4月下旬、6月中旬和7月下旬）相结合，使我们能够将环境中捕获的猎物质量与在牺牲的自由生活蜥蜴胃中发现的节肢动物质量进行比较。4月，当食物丰富度较低且蜥蜴正在繁殖时，盈利能力对大小选择有显著影响，蜥蜴会从除最无利可图的类群之外的所有类群中选择比平均水平更大的猎物。随着活跃季节的推进，食物供应增加，每个胃中的猎物数量减少，平均大小增加。盈利能力对大小选择的影响减小（6月），最终消失（7 - 8月）。这种变化可能与蜥蜴生态的季节性变化有关，例如在繁殖季节将时间最小化作为为非觅食活动节省时间的一种方式，而在繁殖后季节通过选择更少（但更大）的猎物来使移动最小化。因此，我们的数据支持了将盈利能力最大化可能只是陆生变温脊椎动物的一种可选策略这一假设。
