Wildlife-livestock grazing interactions
Herbivory by large ungulates is known to be a primary force structuring ecological communities, and vegetation changes from grazing and browsing are predicted to exert important effects on terrestrial plant and animal communities. Domestic livestock production is the primary use of existing rangelands worldwide; thus, livestock grazing management could be an important tool in the conservation of these ecosystems. Much of my work is aimed at understanding how the timing, duration, and intensity of livestock grazing influences patterns and processes for wildlife in rangeland systems. Current projects assess how grazing-induced changes in vegetation affect population abundance, demography, and the nature and strength of relationships across multiple trophic levels, with a particular focus on birds and mammals. Photo credit: Rick McEwan
Conservation efforts for rare or declining species often rely on habitat restoration as a means of reversing or mitigating negative population trends, and improvements in habitat quality or increased connectivity among habitat patches are expected to increase the probability of persistence for animal populations. Development of effective methods for restoration is increasingly important as restoration ecology becomes an integral tool for wildlife conservation. I am interested in how habitat restoration influences animal demography, habitat selection, species interactions, and the insights it may provide into community assembly.
Wildlife responses to bark beetle-caused tree mortality
Many species of bark beetle are native to coniferous forests of western North America, and are an important source of habitat modification and heterogeneity in these ecosystems. Beetle outbreaks influence succession in pine ecosystems by affecting tree mortality, and can lead to changes in structure or species composition of forests.
Bark beetle outbreaks have important effects on forest wildlife by influencing resource availability or habitat selection. Outbreaks produce dead and decaying trees critical for nesting, roosting, and foraging for many species. Further, bark beetles are a source of food for many bark-foraging birds such as woodpeckers and nuthatches. For these species, beetle epidemics may represent a pulse of resources and increased habitat availability or improved habitat quality. However, for species typically associated with dense canopy cover (e.g., Swainson’s Thrush; Catharus ustulatus) or those relying on mature lodgepole pine as an important source of food (e.g., pine squirrel; Tamiasciurus hudsonicus), bark beetle outbreaks may result in decreased habitat quality. Further, species whose abundance is altered directly through changes in forest structure or stand composition could indirectly influence their predator populations. Thus, beetle outbreaks and associated tree mortality will likely lead to changes in the composition of forest wildlife communities.