Year of Award


Document Type


Degree Type

Doctor of Philosophy (PhD)

Degree Name

Fish and Wildlife Biology

Department or School/College

W.A. Franke College of Forestry and Conservation

Committee Chair

Michael Mitchell

Commitee Members

Douglas Emlen, Angela Luis, Daniel Pletscher, Hugh Robinson, Kevin Podruzny, David Ausband


Behavior, Benefits, Costs, Mechanistic model, Sociality, Territoriality


University of Montana


Territoriality is a fundamental and conspicuous behavior of numerous species, including many carnivores. Although relatively uncommon, carnivore sociality is likewise a conspicuous behavior where it occurs. Territorial and social behavior are of theoretical, empirical, and conservation interest because these behaviors can strongly shape demographic processes. Natural selection has likely shaped animals to make decisions that maximize benefits and minimize costs, but the mechanisms driving territory selection and social decisions remain uncertain. Our goals were to increase understanding of these mechanisms. We furthermore sought to develop reliable methods to predict outcomes of territorial and social behaviors, absent costly monitoring efforts. Gray wolves (Canis lupus) provided a case study for developing and applying mechanistic and predictive models for territory selection and group size.

Chapter 1 presents a mechanistic model for the economics of territory selection. Through simulations, we developed numerous predictions for what may be observed empirically if animals select territories economically based on the benefits of food resources and costs of competition, travel, and predation risk. A literature search demonstrated that the model’s predictions matched empirical observations for many species.

Chapter 2 tests the mechanistic territory model’s predictions on wolves. We analyzed territory sizes of wolf packs in Montana using wolf location data. As predicted, territory size varied inversely with prey abundance, number of nearby competitors, and group size.

Chapter 3 presents further application and tests of the mechanistic territory model. After parameterization with limited, readily-available data, the model produced spatially-explicit predictions for territory location, size, and overlap for the Montana wolf population. It reliably predicted wolf distribution and the territory sizes and locations for specific packs, without using empirical data for wolves.

Chapter 4 presents a predictive model for group size. We demonstrated that wolf pack sizes in Montana were positively related to the local abundance of prey and density of packs, and negatively related to terrain ruggedness, local mortalities, and intensity of harvest management. A predictive model for pack sizes reliably estimated the annual wolf pack sizes observed and illuminated possible underlying mechanisms influencing variation in pack sizes over space and time.



© Copyright 2019 Sarah Nelson Sells