Behavioral Adaptation to a Desert Environment: An Experimental Comparative Study of Food Hoarding

许多动物在食物充足的时候储存食物，以备资源匮乏时使用。囤积食物一般有两种类型：将大量食物储存在一个集中的地方，如洞穴(储物柜囤积)，以及将许多小储藏的食物分散在一个人的家庭范围内(分散囤积)。袋鼠是沙漠啮齿动物，它们将囤积食物作为应对沙漠环境不可预测性的一种策略。共存的袋鼠在它们囤积食物的模式上有所不同：一些物种是囤积者，另一些主要是分散囤积者。这项研究将使用实验室和野外实验来检验关于袋鼠食物囤积模式差异的三个假说。具体地说，由于较大的袋鼠对较小的袋鼠具有进攻性的优势，与Panamint和沙漠袋鼠等较大的动物相比，Merriam和Ord‘s袋鼠等较小的动物应该囤积更少的种子，进行更广泛的分散囤积，并更频繁地移动储藏室以应对盗窃。詹金斯博士还将比较同一物种的不同种群与不同竞争者组合的地点，以检验囤积行为适应特定种群成员所面临的竞争环境的预测。这项研究之所以重要，有几个原因。首先，沙漠啮齿动物一直是研究竞争在生态系统结构和功能中的作用的模式系统。虽然沙漠啮齿动物之间竞争的普遍影响已经得到了很好的证实，但调节竞争的特定行为机制却很少受到关注。作为袋鼠对沙漠环境的关键行为适应，囤积食物可能与物种之间的竞争密切相关。其次，最优觅食是近年来行为生态学研究中最有成效的领域之一，因为理论的发展和对来自理论模型的预测的经验检验之间存在着富有成效的相互作用。作为觅食行为的一个方面，迄今为止，关于囤积食物的研究主要是描述性的。这项关于袋鼠囤积食物的实验研究将把它放在最佳觅食生态的背景下，从而有助于从更广泛的角度研究食物囤积。第三，分散囤积的动物是许多植物物种种子传播的重要媒介。这项导致袋鼠分散囤积与储藏的因素的研究将有助于更好地了解这些动物与沙漠植物种群之间的相互作用，从而有利于沙漠环境的保护。

Many animals store food in times of plenty for use later when resources are scarce. Two general types of food hoarding occur: storing large amounts of food in a centralized location such as a burrow (larder-hoarding), and scattering many small caches of food throughout an individual's home range (scatter-hoarding). Kangaroo rats are desert rodents that use food hoarding as a strategy for dealing with the unpredictability of desert environments. Coexisting kangaroo rats differ in their food- hoarding patterns: some species are larder-hoarders, others are primarily scatter-hoarders. This study will use laboratory and field experiments to test three hypotheses about differences in food-hoarding patterns of kangaroo rats. Specifically, because larger kangaroo rats are aggressively dominant to smaller ones, smaller animals such as Merriam's and Ord's kangaroo rats should larder-hoard fewer seeds, make more widely-spaced scatter-hoards and move caches more often in response to theft than larger animals such as Panamint and desert kangaroo rats. Dr. Jenkins will also compare different populations of the same species from sites with different suites of competitors, to test the prediction that hoarding behavior is adapted to the competitive environment encountered by members of a particular population. This study is important for several reasons. First, desert rodents have been model systems for studies of the role of competition in ecosystem structure and function. Although the pervasive influence of competition among desert rodents has been well established, specific behavioral mechanisms that mediate competition have received little attention. As a key behavioral adaptation of kangaroo rats to desert environments, food hoarding is likely to be closely connected to competition among species. Second, optimal foraging has been one of the most fruitful areas of study in behavioral ecology in recent years because of the productive interplay between development of theory and empirical tests of predictions derived from theoretical models. As an aspect of foraging behavior, work on food hoarding has been mainly descriptive to date. This experimental study of food hoarding by kangaroo rats will contribute to a broader perspective on food hoarding by placing it in the context of optimal foraging ecology. Third, scatter-hoarding animals are important agents of dispersal for the seeds of many plant species. This study of factors that cause kangaroo rats to scatter-hoard vs. larder-hoard will lead to greater understanding of interactions between these animals and desert plant populations, with consequent benefits for conservation of desert environments.