Investigating wildfire history as a driver of large mammal habitat use patterns in a Mediterranean-type ecosystem

Abstract

Fire has historically played a major role in ecosystem stability; however, anthropogenic factors including urban encroachment and climate change are altering the frequency and intensity of fires, resulting in lasting changes to ecosystems. The responses to fire and subsequent habitat use patterns of small mammals are well-studied. However, little is known about how large mammals (>1kg) respond to aspects of fire regimes, and, given that large-bodied species play key roles in ecosystems as herbivores and apex predators, and have substantial habitat range requirements, understanding the effects of fire on their spatial occupancy is particularly important for conservation. I investigated whether large mammal habitat use varies with years-since-fire in the Mediterranean-type ecosystem of Southern California. I collected camera trap presence-absence data on four mammal species (Urocyon cinereoargenteus, Puma concolor, Odocoileus hemionus, and lynx rufus) across three recent wildfires at a conservancy in Irvine, California, and used this data to build a series of generalized linear models. Habitat characteristic data was also collected to correlate the landscape effects of fire with changes in mammal occupancy. I predicted that 1) mule deer would more frequently occupy sites with fewer years-since-fire, and 2) ambush predators (gray fox, mountain lion, and bobcat) would more frequently occupy sites with greater years-since-fire. The model revealed a significant difference in habitat use across time-since-fire categories for two species (mule deer and grey fox), with both more likely to occupy sites with five years since fire than two years since fire. However, a second model demonstrated no significant relationships between vegetation characteristics and habitat use for these two species, suggesting that the effect of time-since-fire on habitat use is mediated by other effects that will need further investigation to discern. The findings of this thesis are important in managing at-risk landscapes; investigating the downstream effects of fire on large mammals and the habitats they occupy is key in informing future land conservation priorities as the planet changes.