Jacob L. Berl

Raccoon (Procyon lotor) Diurnal Den Use within an Intensively Managed Forest in Central West Virginia

Abstract Intensive forest management may influence the availability of suitable den sites for large den-seeking species, such as Procyon lotor (Raccoon). As part of a Raccoon ecology study on an industrial forest in the Allegheny Mountains of central West Virginia, we radio-tracked 32 Raccoons to 175 diurnal den sites to determine relative use of dens that included cavity trees, rock dens, log piles, slash piles, and exposed limbs. Patterns of den use significantly differed between sexes and among seasons. Overall, we recorded 58 cavity dens in 12 tree species with 7 maternal dens found in 5 tree species. Raccoons selected larger-diameter den trees than available cavity trees and non-cavity trees. Because the abundance of suitable tree cavities is known to influence Raccoon densities and recruitment at fine spatial scales and female Raccoons in this study used tree cavities as maternal den sites, the continued harvest of large-diameter trees (i.e., those capable of developing den cavities) without replacement may impact Raccoon recruitment within intensively managed forests throughout the central Appalachians.

Winter Preference for Weed Seed and Waste Grain by Native Mice in Row-Crop Agriculture

Consumption of weed seeds and waste grains by seed predators is an important ecosystem service that helps to regulate weed and volunteer crop populations in many agricultural systems. The prairie deer mouse is found in a variety of sparsely vegetated habitats throughout the central United States and is the dominant vertebrate seed predator in row-crop fields (corn and soybean) in this region. Evaluating the preferences of prairie deer mice for common agricultural weed seeds and waste grain is important to understand the potential ability of native mice to regulate volunteer crops and weed populations. We evaluated winter seed preference of deer mice using cafeteria-style feeding trials presented within row-crop fields in central Indiana and used compositional analysis to compare proportional consumption of seeds from five common agricultural weeds (common ragweed, common cocklebur, common lambsquarters, velvetleaf, and giant foxtail) and two grains (corn and soybean) during overnight feeding trials. Prairie deer mice significantly preferred corn to all other available seed types. Ragweed and soybean were also readily consumed and were preferred over seeds other than corn. Giant foxtail was intermediately preferred. Our results show that prairie deer mice have clear preferences for certain seeds commonly available in row-crop fields; mice likely contribute to reduction of waste grain and some weed seed populations. Nomenclature: Common cocklebur, Xanthium strumarium L.; common ragweed, Ambrosia artemisiifolia L.; common lambsquarters, Chenopodium album L.; giant foxtail, Setaria faberi Herrm.; velvetleaf, Abutilon theophrasti Medik.; corn, Zea mays L.; soybean, Glycine max (L.) Merr.

Seasonal Foraging by Forest Mice Enhances Loss of Weed Seeds from Crop—Field Edges

Abstract Native seed predators, such as mice (Peromyscus spp.) and ground beetles (Carabidae), consume weed seeds and waste grain within agricultural fields and thus provide a potentially important service to farmers. Most previous investigations of agricultural seed predation services have focused on within-field factors that affect rates of seed removal and consumption by field-resident seed predators. However, seasonal migrants from adjacent non-crop habitats may also contribute to removal of weed seed, particularly along field edges. We investigated whether rates of weed seed removal within fields increased during summer crop growth when Peromyscus leucopus noveboracensis (White-Footed Mouse), a ubiquitous forest-dwelling rodent in the eastern US, seasonally migrates into crop fields from adjacent forested woodlots. We used exclosure experiments to quantify the relative number of Setaria faberi (Giant Foxtail) seeds removed from seed trays by vertebrate and invertebrate seed predators within 4 corn fields in central Indiana during 4 different stages of crop growth (emergence [May], vegetative [July], reproductive [August], post-harvest [November]). Seed-removal experiments were coupled with live trapping of rodents and pitfall sampling of invertebrates to identify seed predators. Vertebrates (mice) contributed nearly twice as much (∼50%) to seed removal compared to invertebrates (∼25%), irrespective of season. Rates of invertebrate consumption differed among seasons but were not affected by distance from forest—field edge. Rates of seed removal by mice significantly interacted with season and distance from field edge, with higher rates of seed loss near forest—field edges during July and August even though mouse abundance showed no strong association with distance. Increased seed loss near (within 90 m) forest—field edges was presumably due to consumption by seasonally field-resident White-footed Mice, which constituted the majority (>70%) of mouse captures near field edges. Peromyscus maniculatus bairdii (Prairie Deer Mouse) is a year-round resident in crop fields and most likely contributed to seed loss nearer field interiors, where they comprised >90% of the rodents caught. Although non-crop habitats are often overlooked as a source of seed predation services, our results indicate that forest-dwelling White-footed Mice likely supplement rates of in-field predation on weed seed. Future investigations of seed-predation services should consider the role of resident and seasonally opportunistic seed predators in regulation of weed populations in crop fields.

Predicting harvest vulnerability for a recovering population of American black bears in western Maryland

Abstract Recreational hunting is the tool most commonly used to manage American black bear (Ursus americanus) populations in North America. However, bear populations can be sensitive to overharvest, particularly of mature females that can directly affect population growth. Managers need a thorough understanding of the factors affecting harvest vulnerability when using hunting as a primary management strategy. Here, we coupled Global Positioning System spatial data from female black bears and human hunters in western Maryland, USA, from 2005 to 2007, in order to model bear harvest vulnerability. Specifically, we developed maximum entropy (Maxent) predictive occurrence models for bears and for bear hunters and evaluated the influence of 7 environmental variables on their distributions. We then assessed predicted distribution maps for probability of co-occurrence to identify areas of high and low harvest vulnerability. Slope and land ownership (i.e., private–public) were the 2 most important variables determining female bear distributions, whereas land ownership and cover type were the most important variables influencing hunter distributions. We classified roughly 12% and 16% of the study area as being of high relative use for bears and bear hunters, respectively. Only 5.4% of the study area was considered to have high harvest vulnerability (i.e., high probability of co-occurrence). Areas with high bear relative use but low hunter use (i.e., low harvest vulnerability) comprised 0.9% of the study area. We were most interested in areas of high and low harvest vulnerability to enable resource managers to adjust hunting regulations that meet harvest goals.

Raccoon Spatial Requirements and Multi-Scale Habitat Selection within an Intensively Managed Central Appalachian Forest

Abstract We studied a raccoon (Procyon lotor) population within a managed central Appalachian hardwood forest in West Virginia to investigate the effects of intensive forest management on raccoon spatial requirements and habitat selection. Raccoon home-range (95% utilization distribution) and core-area (50% utilization distribution) size differed between sexes with males maintaining larger (2×) home ranges and core areas than females. Home-range and core-area size did not differ between seasons for either sex. We used compositional analysis to quantify raccoon selection of six different habitat types at multiple spatial scales. Raccoons selected riparian corridors (riparian management zones [RMZ]) and intact forests (> 70 y old) at the core-area spatial scale. RMZs likely were used by raccoons because they provided abundant denning resources (i.e., large-diameter trees) as well as access to water. Habitat composition associated with raccoon foraging locations indicated selection for intact forests, riparian areas, and regenerating harvest (stands <10 y old). Although raccoons were able to utilize multiple habitat types for foraging resources, a selection of intact forest and RMZs at multiple spatial scales indicates the need of mature forest (with large-diameter trees) for this species in managed forests in the central Appalachians.

INTERSPECIFIC COMPARISON OF HANTAVIRUS PREVALENCE IN PEROMYSCUS POPULATIONS FROM A FRAGMENTED AGRO-ECOSYSTEM IN INDIANA, USA

abstract:  Comparatively little is known about hantavirus prevalence within rodent populations from the Midwestern US, where two species of native mice, the prairie deer mouse (Peromyscus maniculatus bairdii) and the white-footed mouse (Peromyscus leucopus noveboracensis), are dominant members of rodent communities. We sampled both species in central Indiana and tested individuals for presence of hantavirus antibodies to determine whether seroprevalence (percent of individuals with antibodies reactive to Sin Nombre virus antigen) differed between species, or among different habitat types within fragmented agro-ecosystems. Prevalence of hantavirus antibodies varied significantly between species, with seroprevalence in prairie deer mice (21.0%) being nearly four times higher than in white-footed mice (5.5%). Seroprevalence was almost eight times higher within the interior of row-crop fields (37.7%) occupied solely by prairie deer mouse populations, relative to field edges (5.2%) or adjacent forest habitat (6.1%). In the fragmented Midwestern agro-ecosystem of this study, prairie deer mice appear to be the dominant hantavirus reservoir, with particularly high seroprevalence in populations within the interior of row-crop fields.

Spatial Variation in Density of White-footed Mice Along Edges in Fragmented Habitat

Abstract The influence of forest fragmentation and associated habitat edges differentially affects forest-dependent organisms, particularly when certain species are able to use resources from surrounding matrix habitats. The white-footed mouse is a forest habitat generalist and is known to disperse among adjoining farmland habitats, including agricultural matrix, in fragmented agro-ecosystems. However, little is known about spatial variation in population density within adjoining farmland habitats or how this relationship varies seasonally. In addition quantifying the extent to which white-footed mice use agricultural matrix as habitat is important for inferring potential ecosystem services (predation of weed seed and waste grain) rendered within row-crop fields. We used spatially explicit capture-recapture models to estimate density of white-footed mice along a gradient of patch (forest fragment) interior to matrix (crop field) interior that spanned fragmented habitat edges. Spatial variation in population density within adjoining habitats was related to the distance from habitat edge, and the magnitude of this relationship (edge effect) varied among seasons and crop cycles within the agricultural matrix. Within-field densities were greater during periods of summer crop growth relative to spring crop emergence or following fall crop harvest. Populations of white-footed mice in forest fragments appear to seasonally spill over from patch habitat into surrounding agricultural matrix. Acquisition of resources from surrounding agricultural matrix may contribute to the inverse density-area relationship observed for white-footed mice within forested habitat in fragmented landscapes. Furthermore, seasonal foraging within matrix habitat likely provides weed seed predation ecosystem services in row-crop fields.

Fine-Scale Movements and Spatial Behaviors of Bear Hunters: Combining GPS With Survey Methods

ABSTRACT Traditionally, information on hunter behavior has been obtained from questionnaires, which are useful, but provide limited information on spatial movements and behaviors. We used a global positioning system (GPS) to track movements of black bear hunters and determine if harvest success was influenced by effort (e.g., time spent afield) and spatial behaviors (e.g., distance traveled from roads). Furthermore, we used mail questionnaires to determine whether hunter perceptions of space use and effort differed from reality (GPS data). Most spatial variables did not differ between hunters and study area averages, indicating that hunters did not select for landscape characteristics differently than expected based on availability. The questionnaires were generally unreliable in describing space use, as hunters overestimated distance traveled from roads and underestimated distances traveled while afield. Studies should consider GPS to obtain more accurate assessments of behaviors while afield. When combined with questionnaire information, GPS data can reveal correction factors to improve spatial behavior estimates.

Low Fecundity of Red-Headed Woodpeckers (Melanerpes erythrocephalus) at the Northern Edge of the Range

ABSTRACT The Red-headed Woodpecker (Melanerpes erythrocephalus) is a threatened bird species undergoing continued population declines across most of its range. Despite the conservation concern, there are few published studies on the species’ fecundity. We examined the nesting phenology, clutch size, and fledging success of Red-headed Woodpecker nests in southern Ontario and northern New York, where population declines are especially pronounced. We calculated the fecundity of the Red-headed Woodpecker populations from fledgling numbers and nest survival estimates. We found that nest phenology and clutch sizes were similar to those reported in other studies for the species. Red-headed Woodpecker nests monitored using video inspection had an unusually low fledging success (39%), and an average fecundity of 0.43 female fledglings per female per year. The fledgling success and fecundity for the monitored Red-headed Woodpecker population was lower than that reported by other published studies on Melanerpes spp., as well as for other genera of woodpeckers. The fecundity was also below the minimum threshold needed to offset mortality for the species, when compared to a majority of minimum fecundity values estimated from the literature. We suggest low fecundity for Red-headed Woodpeckers at the northern edge of their range may be the chronic condition of sink populations, or a more recent phenomenon for small populations approaching local extinction.