Dissertation

Behavioral, Physiological, and Demographic Consequences of Resource Limitation for Large Herbivores

Jesmer, Brett R

2018

Overview

Consumer-resource dynamics are central to the understanding of behavioral, nutritional, and population ecology. Nevertheless, many critical gaps in knowledge remain about the consumer-resource dynamics of large herbivores because their large body size, expansive space use, and slow life histories hinder experimental manipulation. The growth rate of moose (Alces alces) populations across the Intermountain West and other areas of North America has been declining over the past thirty years, but recent (30 to 80 years) translocations of moose have resulted in some relatively small, rapidly growing populations. These translocations therefore created a natural experiment whereby the relationship between resources and the behavior, nutritional, and demography of large-herbivore consumers was evaluated. In chapter one, I integrated a suite of field, laboratory, and remote-sensing techniques with life history theory to understand the role of resource limitation in declining moose recruitment. I found that simple browse surveys and fecal-based measures of forage quality and pregnancy were correlated with recruitment, indicating that these tools can be used to monitor resource limitation. Further, I found that recruitment was dictated ubiquitously by inter-annual variation in weather and regional differences in climate (i.e., average, long-term weather conditions), signifying that all populations were near nutritional carrying capacity. In chapter two, I show how metabolic allometries and state-dependent foraging behavior alter energy-endocrine profiles in large herbivores. Consequently, this chapter both contributes to knowledge about the behavior of large herbivores and illustrates that applying laboratory models of energy-endocrine relationships to large-bodied, free-ranging animals may result in erroneous inference regarding their nutritional condition and proximity to carrying capacity. My third chapter continues to explore how resource limitation influences the foraging behavior of moose by quantifying how diet selection changes as intraspecific competition intensifies and resources become increasingly limiting. Contrary to the Niche Variation Hypothesis, and in accordance with Optimal Foraging Theory, moose broaden their diet selection under resource limitation by increasing individual diet breadth rather than forming into groups of specialized individuals that collectively forage on a wide variety of foods. Although the Niche Variation Hypothesis has gained much attention over the past two decades, my work indicates that inheritance of behavioral or morphological traits associated with foraging (i.e., dietary phenotype) underlie dietary specialization and the Niche Variation Hypothesis; when inheritance of dietary phenotype is weak, populations forage in accordance with Optimal Foraging Theory and individual diet breadth broadens under resource limitation. My fourth chapter tested a long-standing hypothesis in ungulate ecology that predicts migratory behavior is socially learned and culturally transmitted across generations. This hypothesis, however, had not be tested empirically. Using GPS collar data, I compared the migratory propensity of individual moose and bighorn sheep (Ovis canadensis) that were translocated from migratory populations into novel landscapes with the migratory propensity of individuals residing in historical populations that had persisted for at least 200 years. I also compared the ability of individuals to track high-quality, green forage across topographic gradients—a behavior known as “green-wave surfing” that was hypothesized to be a precursor to migration. Individuals failed to migrate when first translocated, but over time (decades) the surfing ability of translocated populations increased and individuals began migrating. Thus, my work demonstrates that the migrations of large herbivores are learned and culturally transmitted from generation to generation, indicating that conservation of migration corridors not only protects the landscapes that these iconic animals depend on, such efforts also maintain the traditional knowledge that migratory animals use to bolster fitness and sustain abundant populations.

• Publisher: ProQuest Dissertations & Theses
• Subject: Ecology / Physiology / Wildlife Management
• ISBN: 0438802063, 9780438802063