Social and Ecological Influences on Maternal and Infant Outcomes in Rwenzori Angolan Colobus Monkeys
Early-life growth and development can have lasting impacts on an animal’s lifetime fitness. These processes are shaped by an animal’s genome and its environment, and the latter can be strongly influenced by its mother (‘maternal effects’). Maternal effects are particularly salient in mammals, as mothers continue to nourish their offspring postnatally through lactation. To best understand the drivers of variation in early-life growth and development, it is essential to study mammals in the ecological and social context in which they evolved. For my thesis, I assessed the impacts of ecological and social factors on (1) infant survival, (2) maternal glucocorticoid concentrations, and (3) infant independence in a population of Rwenzori Angolan colobus monkeys (Colobus angolensis ruwenzorii) in Uganda. These monkeys live in a multi-level society with three tiers of non-random association: the core unit (individuals that feed, rest, and travel together throughout the day), the clan (core units that associate preferentially), and the band (core units that share a home range). First, using six years of data, I found that the immigration of a new male(s) into an infant’s core unit was associated with infant mortality. Deaths did not always occur immediately following male immigration, suggesting that new males may not impact infant survival directly. Second, using physiological data on a subset of the infants’ mothers, I found that fecal glucocorticoid metabolite (FGM) concentrations (a proxy of circulating glucocorticoid concentrations) increased throughout pregnancy and decreased throughout lactation. I also found that FGM concentrations were lower in mothers living in intermediate-sized core units and elevated in mothers living in the same core unit as an immigrant male(s). Third, using behavioural data, I found that infants were more likely to be independent during months when fruit was more abundant and mothers spent less of their time moving, indicating an energetic component to the timing of this developmental milestone. These findings contribute to our understanding of how early life conditions shape mother-infant outcomes by demonstrating that both ecological (fruit availability) and social (e.g., male immigration, core unit size) factors can impact infant survival and independence, as well as maternal physiology.
Allomaternal care, Infant development, Infant survival, Life history theory, Multi-level society, Reproductive physiology
Networked Digital Library of Theses and Dissertations