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Title:Behavioral responses of prairie voles to extrinsic factors and their effects on population dynamics
Author(s):Harper, Steven Jeffrey
Doctoral Committee Chair(s):Batzli, George O.
Department / Program:Biology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Biology, Ecology
Biology, Zoology
Abstract:I investigated the effects of three environmental variables (food quality, predation, and interspecific competition) on agonistic encounters between individual prairie voles (Microtus ochrogaster) to determine if dynamics of populations are influenced by behavioral responses to extrinsic factors. Using a multifactorial, conceptual model, I related direct, indirect, and interactive effects that extrinsic factors should have on behavior, and generated specific predictions regarding responses of voles to experimental manipulations of extrinsic factors. Populations were established in field enclosures and monitored for 24 wk in each of three years. The use of enclosures allowed experimental manipulation of levels of food quality, predation, and interspecific competition (by meadow voles, M. pennsylvanicus) experienced by prairie voles. I estimated the likelihood of agonistic encounters for different types of voles by quantifying simultaneously the likelihood of encounters and the level of aggression elicited by encounters. Likelihood of encounters was estimated by monitoring the number of active runways (via transect surveys), timing and frequency of activity along a runway (via infrared sensors), and utilization of the same runway by different voles (via passive integrated transponder tags). Levels of aggression were estimated by staging dyadic encounters between voles in a neutral arena. Results indicated that factors extrinsic to populations influenced likelihood of encounters and levels of aggression, though not entirely as predicted. In contrast to predicted direct effects (increased aggression with presence of interspecific competitors and decreased aggression with presence of supplemental food) and two-way interactive effects of extrinsic factors on aggression (decreased effect of interspecific competitors with presence of supplemental food), all three manipulated factors interacted to influence aggressive behavior. I could not interpret this complex interaction, but it did not appear to be related to competition for food resources. Likelihood of encounters was influenced directly by extrinsic factors. As predicted, voles were less active in enclosures provided with supplemental food and were more active in those with interspecific competitors. In populations accessible to predators, voles became less active late in the breeding season, when risk of predation was greatest. The likelihood of encounters, but not levels of aggression, was influenced by population density, and, therefore, was influenced indirectly through effects of extrinsic factors on density. Although results indicate that extrinsic factors do have direct, indirect, and interactive effects on some behaviors, changes in social behavior did not affect strongly or consistently the performance of individuals, as determined from estimates of reproduction, survival, dispersal. Therefore, effects of extrinsic factors on density did not depend on the amount of agonistic encounters among individuals. The use of a multifactorial approach was essential for discerning interrelationships among extrinsic and intrinsic factors and for determining the relative influence of these factors on the dynamics of prairie vole populations.
Issue Date:1996
Rights Information:Copyright 1996 Harper, Steven Jeffrey
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9702534
OCLC Identifier:(UMI)AAI9702534

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