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theses

Lactation is the most energetically expensive part of reproduction for female mammals, and species utilize different strategies to overcome these energetic costs. Mother orangutans exhibit multiyear lactation and have the longest lactational period of any mammal, with infants nursing for up to eight years spanning multiple unpredictable fruiting cycles. Still, there is little research on how mothers are able to raise an infant over the course of multiple years. The main goal of this dissertation is to examine the behavioral strategies and consequent physiological responses that mother orangutans use to maximize fitness across periods of infant development. Specifically, I seek to determine 1) if a mother modifies her daily activity, dietary composition, and nutritional intake throughout infant development, 2) how the energetic condition of a mother varies across infant development, and 3) how a mother who lactates across multiple years maintains homeostasis in a relatively marginal and variable energetic environment.
In Chapter Two, I explore mother orangutan behavior by investigating if there is variation in a mother’s activity and feeding behavior. I find that a mother in higher fruiting periods utilizes a strategy that maximizes food intake, especially ripe fruit, while in lower fruiting periods she minimizes her activity to conserve energy while feeding more on non-fruit items. In Chapter Three, I analyze a mother’s caloric and macronutrient intake estimates based on nutritional analyzes of orangutan food items and apply the Geometric Framework of Nutrition to determine if a mother is prioritizing a specific ratio of macronutrients. I find that when a mother has a young infant, she increases her caloric and carbohydrate intake during periods of high fruit available, but cannot do this during low fruit periods and has a much reduced caloric intake. Additionally, during high fruit periods, a mother consumes a similar macronutrient ratio regardless of infant age, and this ratio is potentially the best ratio to build up fat reserves. In Chapter Four, I analyze urinary biomarkers to determine how a mother’s energetic condition varies across her lactation period, and I show that overall, a mother is in her worst energetic condition while she has a young infant during periods of low fruit availability. Collectively, these chapters demonstrate that the greatest period of maternal care in orangutans is while a mother has a two-year-old infant, especially in low periods of fruit availability.

ETD_10313

Ph.D.

Includes bibliographical references

doi:10.7282/t3-few9-em41

ETD doctoral

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