Individual variation in ungulate movement behavior: an examination of the ecological causes and consequences

Abstract

Movement facilitates many essential ecological processes, including dispersal, migration, foraging, disease transmission, and nutrient transport. Over the past decade, movement ecology has transformed from a nascent field to an extremely active area of research. Simultaneously, evidence has accumulated in behavioral ecology on the importance of within-population behavioral variation. In this dissertation, I aim to bridge these fields in the context of ungulate behavior.

In Chapter One, I quantify within-population variation in ungulate space use in two congeneric African antelope species and explore the factors underlying these behavioral differences. I find that differences in nutritional condition promote within-population behavioral

variation, but the relative importance of condition for behavioral decisions varies among species of different sizes.

In Chapter Two, I examine the connection between behavioral variation and the emergent spatial distributions of animals. Using a mechanistic movement model, I demonstrate that models incorporating variation in movement out-perform those that use a single behavioral rule, but have limited effects on the estimated animal spatial distribution.

In Chapter Three, I investigate how predator declines affect within-population variation in ungulate habitat use. After the extirpation of leopards and African wild dogs from Mozambique’s Gorongosa National Park, forest-dwelling antelopes—bushbuck (Tragelaphus

sylvaticus)—expanded into treeless floodplains, where they consumed novel diets and suppressed a common food plant. Simulation of predation risk demonstrated that this behavior was reversible, suggesting that predator restoration can suppress individual variation and rapidly reestablish trophic cascades.

In Chapter Four, I test the proximate behavioral-ecological mechanisms underpinning density-dependent diversification in habitat selection in a recovering African ungulate population. I show that plasticity in foraging behavior and diet selection enabled the Gorongosa waterbuck (Kobus ellipsiprymnus) to tolerate the costs of density-dependent spillover from the high quality floodplain into the lower quality savanna.

Large mammals have important effects on ecosystem functioning, but their large size also makes them vulnerable to direct effects of changing environments on fitness. Conserving these species and their roles in ecological communities requires a greater understanding of behavioral diversity within single populations. Such variation, particularly in animal movements, may determine the capacity of these populations for behavioral buffering under changing conditions.