Spatial and Temporal Structure of a Mesocarnivore Guild in Midwestern North America

Carnivore guilds play a vital role in ecological communities by cascading trophic effects, energy and nutrient transfer, and stabilizing or destabilizing food webs. Consequently, the structure of carnivore guilds can be critical to ecosystem patterns. Body size is a crucial influence on intraguild interactions, because it affects access to prey resources, effectiveness in scramble competition, and vulnerability to intraguild predation. Coyotes (Canis latrans), bobcats(Lynx rufus),grayfoxes(Urocyoncinereoargenteus),raccoons (Procyonlotor), redfoxes(Vulpesvulpes), and striped skunks (Mephitis mephitis) occur sympatrically throughout much of North America and overlap in resourceuse,indicatingpotential forinterspecificinteractions. Although muchisknownabouttheautecology ofthe individual species separately, little is known about factors that facilitate coexistence and how interactions within this guild influence distribution, habitat use, and temporal activity of the smaller carnivores. To assess how habitat autecology and interspecific interactions affect the structure of this widespread carnivore guild, we conducted a large-scale, non-invasive carnivore survey using an occupancy modeling framework. We deployed remote cameras during 3-week surveys to detect carnivores at 1,118 camera locations in 357 2.6-km 2 sections (3-4 cameras/section composing a cluster) in the 16 southernmost counties of Illinois (16,058 km 2 ) during January-April, 2008-2010. We characterized microhabitat at each camera location and landscape-level habitat features for each camera cluster. In a multistage approach, we used information-theoretic methods to evaluate competing models for detection, species-specific habitat occupancy, multispecies co-occupancy, and multiseason (colonization and extinction) occupancy dynamics. We developed occupancy models for each species to represent hypothesized effects of anthropogenic features, prey availability, landscape complexity, and vegetative land cover. We quantified temporal activity patterns of each carnivore species based on their frequency of appearance in photographs. Further, we assessed whether smaller carnivores shifted their diel activity patterns in response to the presence of potential competitors. Of the 102,711 photographs of endothermic animals, we recorded photographs of bobcats (n ¼412 photographs), coyotes (n ¼1,397), gray foxes (n ¼546), raccoons (n ¼40,029), red foxes (n ¼149), and striped skunks (n ¼2,467). Bobcats were active primarily during crepuscular periods, and their activity was reduced with precipitation and higher temperatures. The probability of detecting bobcats decreased after a bobcat photograph was recorded, suggesting avoidance of remote cameras after the first encounter. Across southern Illinois, bobcat occupancyatthecamera-locationandcamera-clusterscale(b clocal ¼0.24 � 0.04,cameracluster b ccluster ¼0.75 � 0.06) was negatively influenced by anthropogenic features and infrastructure. Bobcats had high rates of colonization (b ¼0.86) and low rates of extinction (be ¼0.07), suggesting an expanding population, but agricultural land was less likely to be colonized. Nearly all camera clusters were occupied by coyotes (b ccluster ¼0.95 � 0.03). At the local scale, coyote occupancy (blocal ¼0.58 � 0.03) was higher in hardwood forest stands with open understories than in other areas. Compared to coyotes, gray foxes occupied a smaller portion of the study area (b clocal ¼0.13 � 0.01, bcluster ¼0.29 � 0.03)atallscales.Atthescaleofthecameracluster,grayfoxoccupancywashighestinfragmentedareas withhighproportionsofforest,andpositivelyrelatedtoanthropogenicfeatureswithin100%home-rangebuffers.Red foxesoccupiedasimilarproportionofthestudyareaasgrayfoxes( blocal ¼0.12 � 0.02, b ccluster ¼0.26 � 0.04)butwere morecloselyassociatedwithanthropogenicfeatures.Onlyanthropogenicfeaturemodelsmadeupthe90%confidence set at all scales of analysis for red foxes. Extinction probabilities at the scale of the camera cluster were higher for both gray foxes (be ¼0.57) and red foxes (be ¼0.35) than their colonization rates (gray fox b ¼0.16, red fox b ¼0.06), suggestingbothspeciesmaybedeclininginsouthernIllinois.Stripedskunksoccupiedalargeportionofthestudyarea ( b clocal ¼0.47 � 0.01, b ccluster ¼0.79 � 0.03)andwereassociatedprimarilywithanthropogenicfeatures.Raccoonswere