Date

2017

Document Type

Dissertation

Degree

Doctor of Philosophy

Department

Integrative Biology

First Adviser

Schneider, Jill E.

Other advisers/committee members

Rhinehart, Erin; Rice, Amber; Itzkowitz, Murray

Abstract

This dissertation is a multi-faceted study aimed at understanding how genes, the environment, and development can shape patterns of variation in behaviors related to energy intake, storage, and expenditure. Energy availability is the most important environmental variable that controls reproduction in mammals. However, animals must first survive in order to reproduce. In order to survive, they need functional behaviors to motivate them to forage for food despite environmental heterogeneity, competition, predation, or social cues. The literature on energy balance surprisingly focuses almost entirely on food intake, which is only one component of the behaviors that allow animals to acquire the food resources they need. Animals must first be motivated to gain access to food before eating it; we call these motivational behaviors appetitive ingestive behaviors. There are many gaps in our knowledge about the mechanisms contributing to patterns appetitive behaviors. Appetitive behaviors, like many behaviors, are highly variable. Is variability among individuals consistent over time? Is there underlying genetic variation that selection could act on, or has selection already depleted it? Is variability shaped by the environment? How do these complex traits develop? Here, I take a systematic approach to understanding the origins of variation in an appetitive ingestive behavior called food hoarding. Food hoarding represents the anticipation of future needs. I used Syrian hamsters as a model system because they fail to overeat under conditions of food scarcity, but over-hoard instead. Hoarding can be measured separately from intake. Like humans at grocery stores, hamsters too will focus on the empty cupboards at home and not their empty stomachs. Within a laboratory population, individuals vary but remain consistent over time. Little, if any of the among individual variation is due to the additive effect of genes, but mothers contribute more to offspring phenotype than fathers. I examined the possibility that a maternal contribution is likely programmed during postnatal development by variability in maternal condition during lactation. An adult hamster’s ability to respond to changes in energy balance by eating or hoarding may be pre-determined by the environment in which their brains develop. Like hoarding food, development may anticipate future needs through changes to neuroendocrine mechanisms. I found significant effects of the postnatal maternal environment on the adult morphology (body fat content) and behavior (food hoarding) of the offspring.

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