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Cache Decisions, Competition, and Cognition in the Fox Squirrel, Sciurus niger

机译：福克斯松鼠，黑尾猴的缓存决策，竞争和认知。

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摘要

Caching is the movement and storage of food items by animals for future use. Caching facilitates survival during periods of scarcity, may reduce foraging time during future searches for food, and allows animals to take advantage of periods when available food exceeds current needs. Scatter-hoarding animals store one item per cache, and must employ cognitive strategies to protect their caches. These strategies include assessing the relative value of food items, carefully hiding food items, deceptive behaviors to thwart potential pilferers, and remembering each cache location. Such decisions should be driven by economic variables, such as the value of the individual food items, the scarcity of these items, and competition and risk of pilferage by conspecifics.;My dissertation begins with a general overview of the food-storing literature and the natural caching behavior of the scatter-hoarding fox squirrel ( Sciurus niger). I then describe several experiments that explored the decisions fox squirrels make when storing food. A study examining how fox squirrels adjust effort assessing and caching food based on the food item's value (weight, perishability and nutritional content) using two different foods, hazelnuts and peanuts, is described in Chapter 2. Squirrels ( n = 23) were observed during natural periods of food scarcity (summer) and abundance (fall). Assessment and investment per cache increased when resource value was higher (hazelnuts) or resources were scarcer, but decreased as experimental sessions continued. This study showed that fox squirrels' assessment and caching behaviors were sensitive to both daily and seasonal resource abundance.;Another important problem facing scatter-hoarding animals is how to maximize the retrieval of stored food items while minimizing the risk of pilferage by competitors. One defense against theft could be the spatial placement of caches. I describe a study examining whether the spatial distribution of caches is dependent on nut species in Chapter 3. I measured four key variables of the cache decision: distance and direction traveled, the use of distinct cache areas by nut species, and density of caches. Fox squirrels (n = 48) were tested in 50 sessions, and the geographical coordinates of over 900 cache locations were recorded. Results suggested that squirrels distribute caches using three heuristics: matching the distance traveled before caching to the value of the food item, systematically covering a caching area, and matching cache density to minimize pilferage risk to the highest valued food items. Squirrels spatially chunked their caches by nut species, but only when foraging from a single location. This first demonstration of spatial chunking in a scatter-hoarder underscores the cognitive demand of scatter-hoarding.;I describe a final field study in Chapter 4. A pilot study revealed that there was a high level of pilfering (25%) among a population of fox squirrels. Nineteen fox squirrels cached 294 hazelnuts with passive integrated transponder tags implanted in them. Variables collected included assessment and cache investment and protection behaviors; cache location, substrate, and conspicuousness of each cache; how long each cache remained in its original location, and the location where the cache was finally consumed. polymer chain reaction (PCR) analysis of hair samples obtained from 14 of the subjects was used to determine relatedness among this group of squirrels, and its potential impact on behavior. Results suggest that cache protection behaviors and the lifespan of a cache are dependent on the conspicuousness of a cache. Squirrels may mitigate some of the costs of pilfering by caching closer to the caches of related squirrels than to those of non-related squirrels.;In Chapter 5, I describe a model of the antagonistic relationship between food storing animals and their competitors using agent-based simulations where caching, memory size, and pilfering co-evolve. During periods of food abundance and scarcity, individuals could consume or store found items, retrieve old caches, or pilfer others' caches. In the absence of pilfering, selection is strongest for longer memory. As pilfering increases, shorter memory may be more adaptive, because old caches are likely to be depleted. Contrary to common thought that social interactions enhance cognition, these findings demonstrate how competition may constrain rather than promote some cognitive abilities.;Finally, in Chapter 6, I argue that my research demonstrates that food assessment and cache investment strategies of fox squirrels represent a complex suite of behaviors. These behaviors allow squirrels to maximize the benefits of periods of excess food in the environment, while increasing the likelihood of retrieving nuts later, when food in the environment is scarce. Competition via pilfering influences these food-storing decisions and outcomes, and in some cases, may impair the cognitive abilities of food-storing animals. I discuss the overall implications of this work, and potential directions for future research.
机译：缓存是动物对食品的移动和存储，以备将来使用。缓存有助于在稀缺时期生存，可以减少将来寻找食物时的觅食时间，并允许动物利用可用食物超出当前需求的时期。散布动物会在每个缓存中存储一​​件物品，并且必须采用认知策略来保护其缓存。这些策略包括评估食品的相对价值，小心地隐藏食品，欺骗行为以阻止潜在的盗窃者，并记住每个存储位置。此类决定应由经济变量决定，例如单个食品的价值，这些食品的稀缺性以及竞争和因种而被盗的风险。；我的论文从对食品储藏文献和食品的概述开始。散布的狐狸松鼠（Scuirus niger）的自然缓存行为。然后，我描述了几个实验，探索了狐狸松鼠在存储食物时所做出的决定。第2章描述了一项研究，该研究使用两种不同的食物（榛子和花生）根据食品的价值（重量，易腐烂性和营养成分）评估狐狸松鼠如何调整工作量并缓存食物。在第2章中观察到了松鼠（n = 23）。食物短缺（夏季）和食物丰富（秋季）的自然时期。当资源价值更高（榛子）或资源稀缺时，对每个缓存的评估和投资会增加，但随着实验会话的继续而减少。这项研究表明，狐狸松鼠的评估和缓存行为对每日和季节性资源的丰富度都很敏感。;散布ard积动物面临的另一个重要问题是如何最大程度地获取存储的食物，同时最大程度地减少竞争对手被盗的风险。防止盗窃的一种防御措施可能是缓存的空间放置。在第3章中，我描述了一项研究缓存的空间分布是否取决于坚果种类的研究。我测量了缓存决策的四个关键变量：行进的距离和方向，坚果种类对不同缓存区域的使用以及缓存的密度。狐狸松鼠（n = 48）在50个会话中进行了测试，并记录了900多个缓存位置的地理坐标。结果表明，松鼠使用三种启发式方法分配缓存：将缓存之前行进的距离与食品的价值相匹配，系统地覆盖缓存区域，以及匹配缓存密度以最大程度地降低对价值最高的食品的偷窃风险。松鼠在空间上按坚果种类对它们的缓存进行分块，但仅在从单个位置觅食时才如此。这是散布ard积者中空间分块的第一个演示，突显了散布ho积者的认知需求。我在第4章中描述了最终的实地研究。一项试点研究表明，人口中有很高的盗窃率（25％）。狐狸松鼠。 19只狐狸松鼠储存了294种榛子，其中植入了无源集成应答器标签。收集的变量包括评估，缓存投资和保护行为；缓存位置，底物和每个缓存的显眼性；每个缓存保留其原始位置的时间以及最终消耗缓存的位置。从14位受试者获得的头发样本进行的聚合物链反应（PCR）分析被用于确定这组松鼠之间的相关性及其对行为的潜在影响。结果表明，缓存保护行为和缓存的寿命取决于缓存的显眼性。松鼠通过与相关松鼠的缓存比与非相关松鼠的缓存更近的缓存来减轻偷窃的一些成本。在第5章中，我描述了一种利用代理商-的方法来储藏动物与其竞争者之间的拮抗关系模型。基于缓存，内存大小和窃取共同发展的模拟。在食物丰富和稀缺的时期，个人可能会消耗或存储找到的物品，检索旧的缓存或将他人的缓存盗窃。在没有窃取的情况下，选择最强，可以延长存储时间。随着盗窃行为的增加，较短的内存可能更具适应性，因为旧的缓存可能会用完。与通常认为社交互动会增强认知的想法相反，这些发现表明竞争是如何限制而不是提高某些认知能力的。最后，在第6章中，我认为我的研究表明狐狸松鼠的食物评估和贮藏投资策略代表了一个复杂的过程。一套行为。这些行为使松鼠可以最大限度地利用环境中过量食物的好处，同时增加了当环境中的食物稀缺时以后取回坚果的可能性。通过偷窃进行竞争会影响这些储粮决策和结果，在某些情况下可能会损害储粮动物的认知能力。我讨论了这项工作的总体含义以及未来研究的潜在方向。

著录项

  • 作者

    Delgado, Mikel M.;

  • 作者单位

    University of California, Berkeley.;

  • 授予单位 University of California, Berkeley.;
  • 学科 Animal sciences.;Cognitive psychology.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 93 p.
  • 总页数 93
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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