Abstract. The ability of an animal to acquire enough food to meet its caloric needs is key to its survival and fitness. Understanding the composition of that animal's diet is a crucial element to consider when assessing the species' health and overall role in its ecosystem. We conducted a dietary study of Northern River Otter (Lontra canadensis) at 18 sites across 12 different watersheds in Wisconsin, U.S.A., from summer 2017 through winter 2018. We report the frequency of prey remains found in river otter scats (n = 190) collected at these sites. Fish of any kind appeared in 86% (n = 163) of all scat samples, while crayfish (Cambaridae) were the most commonly occurring individual prey item, appearing in 62% (n = 117) of all scat samples. The second most common prey groups were the bottom feeder fish (Catostomidae and Cyprinidae) group and the panfish (Centrarchidae) group, which both occurred in 45% of all scats. While identifying prey species, we found small, spherical objects that did not appear to be of biological origin in 48% (n = 92) of all scats. After testing the objects using multiple approaches, we confirmed the objects as microbeads, defined as small beads of plastic composition no larger than 5mm in size. This is the first recorded observation of plastic microbeads associated with river otters in North America, and may indicate bioaccumulation of these objects in inland waterways.
Myotis bats have experienced significant population losses due to white-nose syndrome (WNS) throughout large portions of their distributions in eastern North America. As closed-space foragers, these species comprise an important feeding guild within eastern forests. An understanding of where summer populations remain and how their ecology has changed following impact from WNS is needed to assess fully the recovery potential of Myotis bats. We used acoustic sampling, capture surveys, radiotelemetry and roost surveys from 2015 to 2018 to evaluate the status of northern long-eared bat (Myotis septentrionalis) in an eastern Kentucky forest following region-wide impacts from WNS to this species. Acoustic activity of Myotis remained unchanged over the 4 y of sampling, with activity of these bats greatest in mid- to late July. Northern long-eared bats represented 97% of the Myotis captured, indicating activity levels likely reflected patterns for this species. We located 18 roost trees of northern long-eared bats in five tree species, including both live and dead trees. All roost trees were on upper slopes within 100 m of ridge top roads. Maximum exit counts, 24 and 21, at two roosts occurred in late May and early June, suggesting these dates represented the summer maternity period of northern long-eared bats in this forest. Our results demonstrated that post-WNS populations of northern long-eared bats on Robinson Forest formed small colonies, day-roosted in trees near roads on forested ridge tops, were reproductively active, and maintained steady levels of activity across the 4 y of sampling. These data suggest that local populations of northern long-eared bats are surviving WNS and continue to persist during summer months in forests of the Appalachian Mountain region. We hypothesize presence of ridge top roads, often associated with forest logging operations, may be important habitat elements for increasing availability of preferred roosting habitat for summer populations of northern long-eared bats in actively managed forests.
Bird-window collisions (BWCs) constitute a significant source of mortality for both resident and migratory birds. Because windows reflect surrounding landscape components, such as vegetation or sky, birds do not always perceive glass as a barrier. Here we demonstrate a novel technique to classify and quantify reflections in windows on the Radford University campus in southwest Virginia, U.S.A. We deployed a consumer-grade Unmanned Aerial Vehicle, i.e., drone, to photograph 14 contiguous or near-contiguous window columns across five campus buildings in August 2020. For each study aspect, the drone (equipped with an RGB camera) captured images at ca. 5 m altitudinal increments from the ground floor to the roof of each building (three to six images/vertical column). We then manually classified each image in ImageJ to calculate approximate proportions of reflected: (1) vegetation, (2) sky, (3) and artificial structures or impervious surfaces, plus (4) nonreflective glass. We used a generalized linear model to determine how proportional reflections of vegetation, sky, buildings, and nonreflective glass varied across vertical increments. We found the proportion of sky significantly decreased with increasing photo heights, whereas proportion of nonreflective glass significantly increased with increasing heights. This supports previous findings that because birds are drawn to sky reflections, they may collide at relatively lower positions on buildings. Inconsistency in landscape design and building positioning on the campus precluded trends in vegetative or building reflections by height. Our pilot study demonstrates the applicability of a consumer-grade drone for investigating visual characteristics of reflections that influence BWCs from variable observation angles. We suggest the expanded use of drone images as a straightforward technique to measure changes in reflection characteristics from varying degrees of observation. They are a novel method in developing a BWC risk assessment as well as potential mitigation strategies in a suburban or campus environment with buildings of intermediate heights.
Abstract. I describe the phenology of territorial Greater Sandhill Cranes (Grus canadensis tabida) from a long-term (20+ y) marked population near Briggsville, Wisconsin. Territorial adults typically arrived in mid-March (average = 27 Mar., median = 25 Mar.) and egg-laying commenced a median date of 2 wk post-arrival. Chicks typically hatched in mid-May (average and median = 12 May). Renesting occurred from 3-14 d after the first clutch failed and renests hatched from late May to early July (95% CI: 23 May–8 Jul.). Known territorial birds began congregating in mid-Sept, and fall migration typically occurred in late Nov. Territory use by adults occurred at all stages of the annual cycle and may be a way to ensure reclamation of the territory in subsequent years.
Abstract. Species richness and abundances of fluvial specialist fishes often decrease within waters impounded by dams, but mechanisms underlying these decreases are poorly understood. Purpose of this study was to assess the effects of impounded water on fluvial specialist Greenthroat Darter Etheostoma lepidum by quantifying differences in life history (i.e., age structure, life span), reproduction (i.e., gonadosomatic index [GSI], stages of ovarian development), and stomach contents (i.e., diet items and parasites) between a population taken from a lentic environment (Lake Site) and a lotic environment (River Site). Among fishes taken from both sites, Greenthroat Darters lived up to 1.5 y, spawned for 11 mo, and consumed primarily aquatic insects and crustaceans. Differences in reproduction were not detected between populations at the Lake Site and at the River Site. Greenthroat Darters taken from Lake Site consumed fewer diet items, fewer aquatic insects, and greater number of crustaceans than those taken from River Site; however, diet weight, percent stomach fullness, and percent empty stomachs were similar between sites. Greenthroat Darters taken from Lake Site exhibited lower condition factors than those taken from River Site, which corresponded with a greater number of parasites (i.e., Acanthocephala and Nematoda) in individuals taken from Lake Site. Differences quantified herein were not sufficient to cause extirpation of Greenthroat Darters in the impounded waters, given the species has persisted in the impounded water at least since the late 1800s; however, differences in diets and parasites might explain the lower abundance of Greenthroat Darters in Lake Site compared to River Site.
Descendants of introgressive hybridization between species may have evolutionary advantages over their parental species. Prior studies have documented evidence of introgressive hybridization between coyotes, dogs, grey wolves and eastern wolves. This study attempts to attribute morphology and pelage patterns of Pennsylvania coyotes to sex, ecoregion, and the degree of coyote-wolf introgressive hybridization. A total of 192 coyotes were genotyped at 63 ancestry informative SNPS to determine the percent of coyote genome attributable to wolf origin (percent wolf). Females had higher percent wolf than males, which could be the result of lower survivorship in hybrid males. Percent wolf, sex, and ecoregion each were found to independently influence size using general linear model analysis, and the effect of sex was most pronounced. Coyotes from Northeastern and northcentral ecoregions of Pennsylvania were larger in size and possessed a higher percent wolf. Moreover, coyotes with higher percent wolf were larger, less red in some parts of their pelage, and had a different pelage patchiness composition. This correlates with previous studies that showed ecoregions with increased deer density correlated to coyotes with higher percent wolf. Size and percent wolf may be adaptively advantageous in Northeastern Pennsylvania where there is a relatively high deer population abundance. Furthermore, the degree of redness within coyotes may be used as an indicator for introgression levels for population managers, aiding in understanding the shifting ecological role of coyotes.
The unintentional introduction and rapid spread of chestnut blight (caused by Cryphonectria parasitica (Murr.) Barr) in the early 20th century resulted in the demise of American chestnut (Castanea dentata (Marsh.) Borkh.; Fagaceae) as a major component of forest canopies resulting in negative impacts on eastern forest communities. Research efforts over the last century have documented the persistence of occasional trees and root crown/stump sprouts throughout much of the species' historic range, providing the basis for ongoing breeding of blight-resistant trees and restoration efforts. Here we use environmental niche modeling to investigate whether environmentally suitable habitat remains for remnant trees throughout the southwestern historical range, and to evaluate the reintroduction potential of this relatively understudied part of the historical distribution. We also use stage-structured matrix projection models to investigate the potential demographic future of C. dentata near the historical southwestern range limit based on observations of American chestnut in these areas over the last several decades. We found suitable upland habitat with areas of high forest canopy cover occurs throughout much of the southwestern portion of the historical range and that populations of American chestnut in these areas are predicted to drastically decline over the coming decades. These results highlight the continued presence of suitable C. dentata habitat throughout the southwestern extent of its historical distribution, which should be incorporated into evaluations for future reintroduction, and emphasize the need for efforts to locate, conserve, and introduce genetic material from individuals with locally adapted genotypes into active restoration programs.
Patterns of species' occurrences across space and time are fundamental components to understanding their ecology, as this variation often reflects responses to local environmental gradients. We built species-specific models to understand the spatial and temporal factors predicting captures and activity of five snake species in upland pine forests: copperhead (Agkistrodon contortrix), racer (Coluber constrictor), coachwhip (Masticophis flagellum), western ratsnake (Pantherophis obsoletus), and western ribbonsnake (Thamnophis proximus). From mid-May to mid-July across 3 y (2018, 2019, 2020), we monitored boxtraps in two upland pine forests experiencing different management regimes: (1) subjected to frequent thinning and prescribed burning, and (2) subjected to infrequent thinning and prescribed burning. Significantly more copperheads and western ribbonsnakes were captured at the infrequently thinned and burned forest, whereas significantly more racers were captured at forest subjected to frequent thinning and burning. As the summer progressed, captures decreased each subsequent month for both racers and western ratsnakes, with the fewest captures in July. Western ratsnakes were the only species to exhibit a response to the weather in that activity decreased with increasing rainfall. No variables were significant predictors of coachwhip captures. The variation in captures across space may be attributed to the physiological tolerances of each species based on their habitat preferences or differences in prey availability at each forest. Interactions between the physiological tolerances, foraging behaviors, or their reproductive phenology may be underlying the temporal variation in activity patterns.
Small, fragmented populations are at greater risk of extirpation due to reduced genetic diversity from inbreeding and genetic drift. These processes ultimately decrease individual fitness and reduce the ability of a population to adapt. Hill's thistle (Cirsium hillii) is classified as a threatened species throughout much of its range, primarily due to the destruction and fragmentation of its habitat. This study addresses the impact of population size and isolation on the genetic diversity of Hill's thistle. We used microsatellite markers to genotype plants collected from the Lower Peninsula of Michigan in 2001, and from the Lower Peninsula and Drummond Island in 2012, in order to assess genetic differentiation across time and space, as well as to investigate rates of inbreeding in isolated and nonisolated populations. Genetic differentiation between the sample sites in the mainland population of Hill's thistle increased significantly between 2001 and 2012, indicative of increased fragmentation and isolation of the sample sites. However, the 2012 population exhibited lower inbreeding and no difference in heterozygosity or allelic diversity compared to 2001, suggesting the population is stable, or growing, in spite of isolation. Conversely, the population on Drummond Island displayed higher levels of inbreeding and lower number of effective alleles and heterozygosity compared to the mainland, typical of a small, isolated population. Our results indicate that the mainland population of Hill's thistle is persisting but should continue to be monitored demographically due to ongoing habitat loss.
The visual capabilities of prey species such as white-tailed deer (Odocoileus virginianus) must be specialized to enhance predator detection and traverse a complex physical environment. Although aspects of the visual system of deer have been investigated, there has been no evaluation of the species' spatial resolution abilities. We used a behavioral assay to estimate visual acuity of three adult female deer using operant conditioning techniques. We estimated the spatial resolution is between four and six cycles/degree. Our results suggest the white-tailed deer eye allows relatively low spatial resolution, consistent with prior studies that reported high temporal resolution. The combination of low spatial resolution and high temporal resolution allows for efficient detection of movement and enhanced capability to transverse a complex environment.
We assessed a large-scale fish die off event resultant of prolonged anoxic conditions on Grand Lake St. Marys in west central Ohio, U.S., during the summer of 2020, and used this as the basis for comparing long-term species diversity in the lake over the past century. Fish collections were made along a series of shoreline and open water transects, totaling approximately 1.5% of the entire 5220 ha lake area (majority of surveys were shoreline), wherein we identified a total of 12,351 fish comprised of 25 taxa. We used this die off event, combined with recent near shore seine survey data, as an opportunity to assess the modern assemblage structure and to serve as a reference point to prior collected data over the past century. Combining these recent data with historical records, we found that although 57 species have been recorded from the lake dating back to the mid-1800s, only 30 taxa are known to inhabit the lake today. Some of the lost taxa predictably include more intolerant species from the Darter (Percidae), Minnow (Cyprinidae), and Sucker (Catostomidae) families; however, there were also instances of increases in taxa resulting from both state stocking efforts (e.g. Flathead Catfish, Pylodictis olivaris) and natural distribution expansions (e.g. Freshwater Drum, Aplodinotus grunniens). Overall, we attribute the changes to the fish assemblage as negative, given no intolerant taxa currently inhabit the lake. We attribute these long-term changes to watershed wide destruction of natural forest, wetland, and prairie habitats that once typified the region.
Wolf predation of beaver is common in boreal ecosystems, but predation events are thought to be rare in winter. We describe the encounter of a recent wolf predation event of a beaver during conditions of ice cover. The beaver had a broken upper incisor, which may have contributed to it foraging on land during the winter. While it is common for injured animals to have increased vulnerability to predation, injuries can also influence foraging decisions that may indirectly increase vulnerability to predation.
Recolonization by native species following removal of invasive plant species can often be uneven and lead to the rapid increase of one or a few native plant species. This can result in the formation of a significant resource pulse that may consequently affect populations of herbivorous species and their natural enemies. Here we present results from observations of parasitism rates during a localized outbreak of the Asimina webworm moth, Omphalocera munroei, a locally monophagous herbivore of the common paw-paw. Asimina triloba. This outbreak initiated from locations of increased understory growth of A. triloba, following the removal of Amur Honeysuckle (Lonicera maackii). Parasitism rates during the outbreak reached 50%, with higher parasitism rates observed in larvae collected at the end of the local outbreak relative to those the year following the peak of the outbreak. Parasitism rates remained high 3 y after the end of the local O. munroei outbreak, indicating >7 y of high parasitoid densities. O. munroei emerges late in the growing season, making it fairly inaccessible as a host or prey to many generalist predators/parasitoids, which emerge earlier the following year. This suggests the O. munroei outbreak potentially contributed to an increase in natural enemy pressure of other native species in the community.
Lakes and reservoirs are frequently monitored by researchers for elevated mercury concentrations in sportfish. Rivers and streams, especially those of smaller orders, are less frequently monitored for mercury contamination and nonsport fishes and invertebrates, although important components of the food web, are rarely examined. We addressed this gap by surveying mercury levels in a stream community in the Kiamichi River in southeastern Oklahoma, U.S., by sampling fish and macroinvertebrates at ten sites in the river. We found elevated levels of mercury across taxa within the river including individuals of smallmouth bass populations 10-25 cm in length having concentrations (2986 +/- 1053 ng/g dry weight) above the U.S. Environmental Protection Agency human limit. Furthermore, we observed high concentrations in darters and logperch (1133 +/- 464 ng/g dry weight), nonsport fishes found predominantly in rivers and streams. Our results indicate mercury contamination can reach elevated concentrations in rivers and stream food webs, posing risks to both humans and wildlife.
Amphibians are a highly vulnerable taxonomic group that have suffered population declines worldwide. As amphibians serve critical links between trophic levels and facilitate nutrient recycling, it is critical to understand how their species richness, abundance, and phenology shift over time. Because amphibian populations naturally fluctuate, short-term monitoring can provide insight into how amphibian communities respond to proximate changes in weather conditions, which is helpful for predicting long-term responses to climate change. We used pitfall traps to examine interannual variation of the amphibian community at Powdermill Nature Reserve (PNR) in Pennsylvania during 2020-2021 to provide critical details for future long-term monitoring. Mean monthly temperature and precipitation did not vary significantly between years, but monthly captures per sampling effort declined and monthly biomass per sampling effort increased from 2020 to 2021. Despite a lack of significant relationships between total amphibian captures and temperature and precipitation, peak abundance shifted earlier, and individuals were larger in 2021 compared to 2020. Interestingly, individual species biomass was predicted by an interaction between temperature and precipitation, suggesting individual species will vary in vulnerability to climate change, but the amphibian community as a whole at PNR is resilient to minor fluctuations in temperature and precipitation.
Based on daily collections of final instar exuviae, the widespread annual cicada adult emergence of Neotibicen canicularis (Harris) (Hemiptera: Cicadidae) was studied in southeastern Wisconsin in a combined plot containing 15 mature trees and suburban lawns for seven successive years and in a separate plot of two trees for four years. The daily numbers of males and females were recorded. Over the entire seven years of the 15-tree plot, total female and male exuviae were equal, a summative 50:50 ratio. However, there was considerable deviation from this ratio three of the seven years. More females than males eclosed in the first two years and more males eclosed in the final year, yet the overall trend was for females to eclose later than males for the entire seven-year study of the 15-tree plot, with many more females emerging in the last twenty plus days. Although ambient temperatures varied over the study (cooler in the first two years and warmer later), they did not have any discernible effect on the timing of female and male eclosions. The overall annual emergence period was 56.7 (SE 4.48) d for a seven-year total of 2967 exuviae, with the annual average emergence being 437.6 (SE 34.6) per year. The average density of exuviae, an estimate of the emerging adult population, was 1.3 +/- 0.09 (SE) per m(2). In the separate two-tree plot, a greater number of males emerged than females for all four years.
Although it is known that southern flying squirrels (Glaticomys volans) nest in larger groups to offset the energetic costs of low temper:mires. the influence of other variables on aggregation size remains relatively unknown. Therefore, the influence of environmental variables and individual characteristics of G. volans on nest box aggregation size was studied from 1992-1998 at the Savannah River Site in South Carolina. Over the study period, 5859 occupied boxes were observed, representing 11,238 captures and 2671 unique individuals. The majority of occupied boxes (60.3%) contained solitary individuals, while 26.1% contained aggregations (>= 2 individuals) of adult and/or subadult individuals and 13.6% contained litters. Although ambient temperature is widely believed to be the most important variable influencing aggregation size of G. volans, the final model explaining nest aggregation size for G. volans included not only minimum daily ambient temperature, but also Julian date and individual G. volans characteristics of sex, age, and reproductive status. Minimum ambient temperature was inversely related to aggregation size, with larger aggregation sizes associated with winter months, although aggregation size sharply increased between the months of Aug.- Sept. The retention of Julian date in the final model, in addition to minimum ambient temperature, indicates that behavioral shifts due to seasonal changes, independent of temperature, should be considered. Nestlings were associated with larger aggregation sizes, as were inactive and lactating females and inactive males. However, sex alone did not significantly contribute to the final model. This study demonstrates that in addition to temperature, there are a suite of predictors of nest aggregation size for G. volans that should be considered when evaluating nest box occupancy for this species.
Alpine ecosystems in the arid southwestern United States are vulnerable to climate change. Many of these ecosystems are experiencing increased recreational use and introductions of nonindigenous ungulates. In the La Sal Mountains of southeastern Utah, alpine plant communities support an endemic plant species, Erigeron mancus, 11 plant and two animal species of conservation concern, and a United States Department of Agriculture (USDA) Forest Service Research Natural Area. Nonindigenous mountain goats (Oreamnos americanus) were introduced by the Utah Division of Wildlife Resources (UDWR) in 2013 and 2014, and recreational use has increased in the intervening period. To evaluate potential effects of mountain goat and recreational use, vegetation monitoring was initiated by the USDA Forest Service in 2016. We used 5 y monitoring data (2016-2020) and generalized linear mixed models to analyze the separate and interacting effects of year, recreational use, and mountain goat use on: (1) populations of plant species of conservation concern; (2) vascular and nonvascular plant cover; and (3) ground cover. Our analyses revealed decreases in proportional frequency of E. mancus at the end of the monitoring. Proportional cover of dominant plant growth forms, especially forbs, declined, while proportional cover of litter and ineffective ground cover (bare soil and pavement) increased. Recreational or goat use were a factor in several of the observed changes, although weather and climate likely also influenced the results. Management complexity arises because of the different missions of USDA Forest Service and UDWR, but adjustments in mountain goat numbers and recreational use may be needed to maintain ecologically resilient ecosystems. Continued monitoring can provide the basis for adaptive management.
Despite their visibility, abundance, and widespread distribution, the movements of Isabella moth larvae (a.k.a "woolly worms:'' Pyrrharctia isabella (J.E. Smith); Lepidoptera: Erebidae: Arctiinae) have been poorly studied. We observed these larvae to assess the relationship between their movement and local environmental conditions. Twice each day for 83 d, nearly 52 km of highway were observed in northwest Missouri. A total of 264 larvae were encountered during 664 total visits to four road sections, peaking in the first week of October. Analyses revealed increased larva abundance (n >= 159 road-section visits) associated with temperature, wind speed, pale pavement tint, and afternoon time-of-day. The best overall model to explain larval movement patterns, based on 163 visits and all measured conditions, incorporated temperature, north wind speed, west wind speed, and humidity (P = 0.015), but no other factors. In addition, larvae showed a significant tendency to travel in the same direction as the wind, and to travel eastward in the afternoons. These observations provide insights into the fall movements of a common larva, and provide directions for future research.
Small mammals are ubiquitous members of vertebrate communities that are sensitive to habitat change. In the Great Lakes region of North America, small mammal communities have changed rapidly, but experimental tests of potential mechanisms are lacking. Using a before-alter, control-treatment design, we quantified the response of small mammals to single-tree selection harvest in Laurentian hardwood forests of Wisconsin, United States. We documented changes in forest structure and small mammal abundance, species diversity, and community similarity from silvicultural treatment. Treatment reduced tree density and canopy cover and increased mean tree diameter, woody stern density, variation in woody stem density, and volume of coarse woody debris. Peromyscus and northern short-tailed shrews (Blarina brevicauda) were dominant community members across treatments and years. White-footed mice (P. leucopus) outnumbered woodland deer mice (P. maniculatus gracilis) before treatment, but declined by almost fifty percent after treatment; deer mice and total rodent (i.e., Rodentia) abundances were unchanged. Small mammal species diversity increased twofold following treatment. Our experiment identified species-specific responses within Peromyscus to timber harvest: white-footed mice, the numerically dominant and generalist species, were most sensitive to habitat change, and their response produced cascading effects to small mammal community .structure. Future experiments should assess these small mammal responses in a multi-year framework and quantify their effects on the broader vertebrate community.
