Michael J. Cherry

Coyote diets in a longleaf pine ecosystem

The ecological implications of coyote Canis latrans colonization of the eastern USA have drawn considerable interest from land managers and the general public. The ability to predict how these ecosystems, which have lacked larger predators for decades, would respond to the invasion of this highly adaptable species needs an understanding of coyote foraging behavior given local resource availability. Therefore, we examined the diet of coyotes in a longleaf pine Pinus palustrus ecosystem from 2007–2012. We examined 673 coyote scats collected on the Joseph W. Jones Ecological Research Center in southwestern Georgia. We observed considerable seasonality in coyote use of rodents, white-tailed deer Odocoileus virginianus, rabbits and vegetation. Coyotes exploited anthropogenic food sources, particularly waste peanuts Arachis hypogaea, during the fall and winter when native soft mast was not available. Adult white-tailed deer were consumed during every month and was not limited to the pulse of carrion availability from hunter-harvested animals, suggesting the use of adult white-tailed deer may not be restricted to scavenging in this system. We found mesomammals, including armadillos Dasypus novemcinctus, raccoons Procyon lotor, Virginia opossums Didelphis viginiana, bobcats Lynx rufus, grey foxes Urocyon cineroargenteus and striped skunks Mephitis mephitis in approximately 18% of coyote scats from January–August. On our site, and some adjacent properties, the use of predator trapping focused primarily on Virginia opossum, raccoon, coyote, bobcat and gray fox, to increase northern bobwhite Colinus virginianus production may have resulted in increased use of mesomammals through scavenging. We offer evidence that coyote colonization may alter food web dynamics in longleaf pine ecosystems through depredation of white-tailed deer and by influencing the mesomammal guild through direct predation and competition for rodents, rabbits, carrion and soft mast.

Are camera surveys useful for assessing recruitment in white-tailed deer?

Camera surveys commonly are used by managers and hunters to estimate white-tailed deer Odocoileus virginianus density and demographic rates. Though studies have documented biases and inaccuracies in the camera survey methodology, camera traps remain popular due to ease of use, cost-effectiveness, and ability to survey large areas. Because recruitment is a key parameter in ungulate population dynamics, there is a growing need to test the effectiveness of camera surveys for assessing fawn recruitment. At Savannah River Site, South Carolina, we used six years of camera-based recruitment estimates (i.e. fawn:doe ratio) to predict concurrently collected annual radiotag-based survival estimates. The coefficient of determination (R2) was 0.445, indicating some support for the viability of cameras to reflect recruitment. We added two years of data from Fort Bragg Military Installation, North Carolina, which improved R2 to 0.621 without accounting for site-specific variability. Also, we evaluated the correlation between year-to-year changes in recruitment and survival using the Savannah River Site data; R2 was 0.758, suggesting that camera-based recruitment could be useful as an indicator of the trend in survival. Because so few researchers concurrently estimate survival and camera-based recruitment, examining this relationship at larger spatial scales while controlling for numerous confounding variables remains difficult. Future research should test the validity of our results from other areas with varying deer and camera densities, as site (e.g. presence of feral pigs Sus scrofa) and demographic (e.g. fawn age at time of camera survey) parameters may have a large influence on detectability. Until such biases are fully quantified, we urge researchers and managers to use caution when advocating the use of camera-based recruitment estimates.

Breeding chronology and social interactions affect ungulate foraging behavior at a concentrated food resource

Prey species must balance predator avoidance behavior with other essential activities including foraging, breeding, and social interactions. Anti-predator behaviors such as vigilance can impede resource acquisition rates by altering foraging behavior. However, in addition to predation risk, foraging behavior may also be affected by socio-sexual factors including breeding chronology and social interactions. Therefore, we investigated how time-of-day, distance-to-forest, group size, social interactions (presence of different sex-age class), and breeding chronology (pre-breeding, breeding, post-breeding seasons) affected probability of feeding (hereafter: feeding) for different sex and age-classes (mature males, immature males, adult females, and juveniles) of white-tailed deer at feed sites. We developed a set of candidate models consisting of social, habitat, reproductive, and abiotic factors and combinations of these factors. We then used generalized linear mixed models (GLMMs) to estimate the probability of feeding and used model averaging of competing models for multimodel inference. Each adult sex-age class’ feeding was influenced by breeding chronology. Juveniles were more likely to be feeding than adults in all seasons. Feeding increased with group size for all sex-age classes. The presence of a mature male negatively influenced the feeding of immature males and juveniles were more likely to be feeding when an adult female was present. Feeding decreased with increasing distance-to-forest for mature males but not for other sex-age classes. Our results indicate that each sex-age class modulates vigilance levels in response to socio-sexual factors according to the unique pressures placed upon them by their reproductive status and social rank.

Gray fox home range, spatial overlap, mated pair interactions and extra-territorial forays in southwestern Georgia, USA

Despite numerous studies estimating gray fox Urocyon cinereoargenteus home range sizes, there have been few studies to evaluate more nuanced space use patterns; thus little is known about gray fox spatial ecology beyond estimates of home range size. We used GPS-technology to track 34 gray foxes (20 males and 14 females) from February 2014 until December 2015 in southwestern Georgia, USA. Home range sizes were similar among seasons (p > 0.05), but core area sizes were smaller during spring than during winter and summer (p < 0.05). As would be expected, home range overlap was much greater between mated pairs than among neighboring animals and core area overlap among neighbors did not occur. Members of a mated pair apparently interacted frequently, with 29.4% of all simultaneous locations occurring within 40 m of each other. Members of mated pairs interacted more diurnally during spring (49.9%) which is concurrent with denning, than during summer (31.5%), while nocturnal interactions were similar during spring (18.0%) and summer (19.3%). We recorded 25 extra-territorial forays from 10 of 26 gray foxes. Three male foxes were responsible for nearly half (12) of these forays. Because these forays took place during the breeding season, we suggest males may have been seeking extra-pair copulations.

Habitat selection and diurnal refugia of gray foxes in southwestern Georgia, USA

Understanding habitat selection of gray foxes (Urocyon cinereoargenteus) is essential to evaluate their potential response to changes in land use and predator communities. Few studies have evaluated temporal habitat selection or explicitly identified habitats used by gray foxes for diurnal refugia. We used GPS collars to obtain location data for 34 gray foxes (20 males and 14 females) from February 2014 to December 2015 to evaluate temporal (seasonal and diel) habitat selection and selection of diurnal refugia in southwestern Georgia, USA. We analyzed habitat selection at 2 levels, selection of a core area within the home range and selection of locations within the home range. Habitat selection was non-random (P < 0.001) but consistent among seasons, between day and night, and between sexes (P > 0.05). Hardwoods, human use (i.e., areas associated with regular human activity such as buildings, lawns, parking areas, etc.), and roads were selected (P < 0.05), whereas pine dominated stands were used randomly (P > 0.05). Selection of habitats for diurnal refugia did not vary seasonally or by sex (P > 0.05), with foxes selecting (P < 0.05) areas near hardwood forests, roads, agriculture, human use, pastures/food plots, and shrub scrub habitats. Gray foxes were observed on the ground while resting, and we found no evidence of gray foxes diurnally resting in trees. Our results suggest that on our study area, gray foxes are an edge species that prefer forests with a hardwood component in areas near human use and roads.