Bradley S. Cohen

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.

ISOLATION AND GENOTYPIC CHARACTERIZATION OF TRUEPERELLA (ARCANOBACTERIUM) PYOGENES RECOVERED FROM ACTIVE CRANIAL ABSCESS INFECTIONS OF MALE WHITE-TAILED DEER (ODOCOILEUS VIRGINIANUS)

Abstract:  Trueperella (Arcanobacterium) pyogenes is a causative agent of suppurative infections in domestic and wild animals. In some populations of captive or free-ranging white-tailed deer (Odocoileus virginianus), cranial abscess disease is an important source of mortality in adult males. Although the pathogenesis of this disease is poorly understood, T. pyogenes has been isolated from active infections with other opportunistic bacteria. In this study, bacteria associated with cranial abscess infections were identified, the prevalence of T. pyogenes associated with these infections was determined, and the presence of known virulence determinants in T. pyogenes isolates was ascertained. Using routine biochemical techniques seven bacterial species were identified from 65 samples taken from active cranial abscess infections of 65 male white-tailed deer. Trueperella pyogenes was recovered from 46 samples; in 32 samples it was the only bacterium species detected. Staphylococcus aureus was detected in 26 samples. From these samples, the presence of known and putative virulence genes of T. pyogenes—plo, nanH, nanP, cbpA, fimA, fimC, fimE, and fimG—was examined by conventional polymerase chain reaction. All T. pyogenes isolates were positive for the pyolysin genes plo, nanP, and fimA. Furthermore, nanH, fimA, fimC, and fimE were detected in over 70% of isolates. Of the isolates tested, 48% had genotypes containing all virulence genes except cbpA. The suggestive virulence potential of all isolates, coupled with the large number of pure cultures obtained, implies that T. pyogenes is a causative agent of cranial abscess disease.

Epethelial Presence of Trueperella pyogenes Predicts Site-Level Presence of Cranial Abscess Disease in White-Tailed Deer (Odocoileus virginianus)

Cranial/intracranial abscess disease is an emerging source of significant mortality for male white-tailed deer (Odocoileus virginianus). Most cases of cranial/intracranial abscess disease are associated with infection by the opportunistic pathogen Trueperella pyogenes although the relationship between the prevalence of the bacteria and occurrence of disease is speculative. We examined 5,612 hunter-harvested deer from 29 sites across all physiographic provinces in Georgia for evidence of cranial abscess disease and sampled the forehead, lingual, and nasal surfaces from 692 deer. We used polymerase chain reaction (PCR) to determine presence of T. pyogenes from these samples. We found T. pyogenes prevalence at a site was a predictor for the occurrence of cranial abscess disease. Prevalence of T. pyogenes did not differ between samples from the nose or tongue although prevalence along the forehead was greater for males than females (p = 0.04), particularly at sites with high occurrence of this disease. Socio-sexual behaviors, bacterial prevalence, or physiological characteristics may predispose male deer to intracranial/cranial abscess disease. Determination of factors that affect T. pyogenes prevalence among sites may help explain the occurrence of this disease among populations.

EPIZOOTIOLOGY OF CRANIAL ABSCESS DISEASE IN WHITE-TAILED DEER (ODOCOILEUS VIRGINIANUS) OF GEORGIA, USA

Abstract Intracranial abscess disease is a cause of natural mortality for mature male white-tailed deer (Odocoileus virginianus). Most cases of abscesses are associated with bacterial infection by Trueperella (Arcanobacterium) pyogenes, but a complete understanding of the epidemiology of this disease is lacking. We quantified the effects of individual characteristics, site-specific herd demographics, land cover, and soil variables in estimating the probability of this disease. We examined 7,545 white-tailed deer from 60 sites throughout Georgia US for signs of cranial abscesses, the predecessor of intracranial abscesses, and recorded the presence or absence of cranial abscesses for each individual examined. We detected no cranial abscesses in 2,562 female deer but 91 abscesses in 4,983 male deer examined (1.8%). A generalized linear mixed model, treating site as a random effect, was used to examine several potential explanatory risk factors including site-level landscape and soil characteristics (soil and forest type), demographic factors (deer density and male to female ratio), and individual host factors (deer sex and age). Model results indicated that the probability of a male having a cranial abscess increased with age and that adult sex ratio (male:female) was positively associated with this disease. Site-specific variables for land cover and soil types were not strongly associated with observations of the disease at the scale measured and a large amount of among-site variability remained. Given the demonstrated effect of age, gender, and local sex ratios but the remaining unexplained spatial variability, additional investigation into spatiotemporal variation of the presumed bacterial causative agent of cranial abscesses appears warranted.

Spring Excursions of Mature Male White-tailed Deer (Odocoileus virginianus) in North Central Pennsylvania

Abstract During the breeding season, male white-tailed deer (Odocoileus virginianus)have been reported to take excursions outside of their normal home ranges, likely in search of receptive females. However, we documented additional excursive movements by males during spring in north central Pennsylvania. From December 2011 – April 2012, we equipped 13 mature (≥2.5 y old) male white-tailed deer with global positioning system (GPS) collars programmed to record locations hourly. We defined an excursion as any occasion where a male traveled ≥1.6 km outside of its 95% home range boundaries for ≥12 h. Between 6 April and 6 June 2012, nine males (69.2%) made excursions with six making ≥2 excursions. Mean total path distance and duration of excursions was 4.0 km (range  =  1.7-8.0 km) and 22 h (range  =  12–40 h), respectively. Although the reason for spring excursions is obscure, hypotheses such as increased doe aggression before parturition, males returning to natal home ranges, or visitation to mineral sites do not appear tenable based on current observations.

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.

Color perception influences microhabitat selection of refugia and affects monitoring success for a cryptic anuran species.

Perceptual-biases are important for understanding an animals natural history, identifying potential ecological traps, and for developing effective means to monitor individuals and populations. Despite research demonstrating anurans having a positive phototactic response towards blue colors, we do not yet understand if color cues are used functionally beyond sexual selection. The aim of our study was to determine if color cues are used in selecting microhabitat, and if anurans blue-positive phototactic response could increase selection of artificial PVC refugia used to monitor cryptic camouflaging anuran species. We captured 32 Copes Gray Treefrogs and placed them in mesh enclosures with three PVC tubes painted blue, brown, and white. Concurrently, we placed blue, brown, or unpainted white PVC tubes in stratified arrays around a treefrog breeding pond, and counted the number of occasions treefrogs occupied different colored PVC tubes. In the confined choice experiment, treefrogs selected blue tubes (48.3%) significantly more often than brown (28.5%) or white (23.2%) tubes. Our field experiment mirrored these findings (52.0% of capture events in blue, 29.0% in brown, and 19.0% in unpainted white tubes). Our results suggest color influences Copes Gray Treefrog microhabitat selection, and they utilize color vision when choosing refugia. We demonstrate simple, small changes based on perceptual-biases can induce behaviors that may in turn have large impacts on sampling techniques used in monitoring and inventorying. Incorporating non-traditional physiological measures into animal inventorying and monitoring programs can be used in the future to improve conservation efforts.

Bacterial Fauna of the Forehead, Tongue, and Nasal Mucosa of Odocoileus virginianus (White-Tailed Deer) in Georgia

Abstract Identification of the bacterial fauna associated with the skin, nasal mucosa, and tongue of Odocoileus virginianus (White-tailed Deer) may provide some insight into deer health and potential risks for humans from contact with deer. Few bacterial surveys have investigated White-tailed Deer, despite the commonality of human—deer interactions. From October to December 2011, we collected swab samples from the forehead, nose, and tongue of 39 hunter-harvested White-tailed Deer in Georgia. We inoculated and incubated agar plates for 48 h at 35 °C and identified the isolated bacterial colonies to genus using the bioMerieux Vitek 2 system. We amplified and sequenced portions of the 16s ribosomal-RNA gene, and used the products to identify 60 species of bacteria, including 342 Gram-positive isolates and 93 Gram-negative isolates. Although most species isolated from White-tailed Deer were nonpathogenic environmental bacteria, good hygiene is recommended when handling these animals.