Publication Date

1989

Document Type

Dissertation/Thesis

First Advisor

Ende, Carl von

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences

LCSH

Animals--Food; Fox squirrel--Food

Abstract

Animals dependent upon cached resources must allocate foraging effort to both consuming and hoarding prey items. To examine the relationship between the number of prey items consumed and the number hoarded by individuals over daily and seasonal time, I conducted artificial patch-feeding experiments on a population of free-ranging, individually marked fox squirrels (Sciurus niger). California walnuts were provided at a constant patch density in day-long feeding trials replicated weekly over nine months in a northern Illinois park. The proportion of all nuts removed that were consumed tended to decrease throughout the day, while the proportion of nuts hoarded increased. Foraging rates, handling times, and the proportion of nuts consumed showed significant quadratic seasonal time trends with winter minima or maxima. In addition, individuals displayed consistent consuming and hoarding patterns unrelated to age or gender. I defined two foraging types: (1) Consumers, animals that consumed proportionately more prey than they hoarded and had high prey intake rates and total daily consumption; and (2) Hoarders, animals that hoarded proportionately more prey than they consumed, had high hoarding rates and lower total daily consumption. The differences between the types remained distinct over time. Hoarding was relatively static in Consumers but was highly plastic in Hoarders. Both types had similar prey-handling times and locations, and oriented caches toward den trees. To determine whether these individuals' foraging patterns were fixed or a response to specific nut species, I conducted a similar series of experiments using three prey types: California walnuts (CWN), shagbark hickory nuts (SH), and red oak acorns (RO). Both Consumers and Hoarders consumed proportionately more of the nuts containing higher energy per gram when presented monospecifically (CWN=SH>RO), and more of the prey with higher total energy when presented simultaneously (CWN>SH). Handling times were similar for CWN and SH consumed (CWN=SH>RO), but not for those hoarded (CWN>SH=RO), suggesting that the quantity of prey consumed or hoarded was influenced by prey quality, while handling location decisions were influenced by prey size. Although Consumers and Hoarders spent comparable amounts of time foraging on each prey type, they continued to significantly differ in proportion consumption of all species.

Comments

Includes bibliographical references (pages 97-105)

Extent

viii, 105 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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