Available at: https://digitalcommons.calpoly.edu/theses/3114
Date of Award
6-2025
Degree Name
MS in Biological Sciences
Department/Program
Biological Sciences
College
College of Science and Mathematics
Advisor
Tim Bean
Advisor Department
Biological Sciences
Advisor College
College of Science and Mathematics
Abstract
Understanding factors that affect how animals select their home ranges is critical for proper species management, especially for threatened and endemic species. Density-dependent factors can be particularly difficult to understand because studying them requires large fluctuations in population size. The island fox (Urocyon littoralis), endemic to the California Channel Islands, has experienced dramatic fluctuations in population size making it an excellent candidate for studying the effects of density on home range size and habitat selection. In 2009, researchers on Santa Rosa Island took advantage of this “natural experiment” to document fox home ranges and habitat selection at a low population density. The fox population has since recovered, which provided an ideal opportunity to examine the same population under dramatically different densities to determine the effect of population density on home range size and composition. We collected GPS data from foxes in a high-density fox population on Santa Rosa Island and directly compared the resulting home range size, overlap, and habitat selection to data collected from the low-density population in the same area in 2009. Fox home range size displayed negative density dependence, as the mean home range size was 83% smaller at high densities than at low densities. Home range overlap was very low and not density-dependent. Habitat selection was density-dependent, with foxes at high densities displaying less selection overall than foxes at low densities. Vegetation type was the leading predictor for habitat selection at high- and low-densities, with foxes selecting for shrubland and against barren land regardless of fox population density. This study suggests that these generalist omnivores become more likely to use habitat in proportion to its availability at high population densities due to constraints from intraspecific competition and preservation of territoriality. Results of this study also highlight the importance of maintaining quality habitat across the entire island, as the foxes are constrained to small home ranges and forced to use all spaces, including those with less suitable habitats.
Award received:
Best Student Oral Presentation at the Western Section of The Wildlife Society 2024 meeting