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Population characteristics and life history aspects of healthy mussel populations are poorly understood. The reproductive cycle, age and growth, and population structure of Obovaria subrotunda were examined at four sites in the middle Duck River, Tennessee. Obovaria subrotunda was confirmed to be a bradytictic species, spawning in the late summer and holding glochidia in the gills for 11 mo until the following summer. Fecundity was positively related to mussel length (R2 = 0.75) and ranged from 7122 to 76,584 glochidia. Fourteen species of fish found in the Duck River, in the families Percidae, Cyprinidae, and Cottidae, were infested with glochidia in the laboratory to examine potential hosts. Juveniles transformed on Etheostoma blennioides (greenside darter), E. obama (spangled darter), E. flabellare (fantail darter), and Cottus carolinae (banded sculpin). Analyses of shell thin-sections indicated that males grew faster and obtained a larger size than females. Individuals live to at least 14 y old. Females became sexually mature at age one. Four sites were quantitatively sampled using a systematic design with three random starts. The observed ratio of adult males to females (0.9∶1) did not differ significantly from 1∶1. Results of the quantitative sampling showed an increase in density compared to earlier studies and a high proportion of 1 to 5 y old O. subrotunda.
Excavations at an archeological site adjacent to the Verdigris River in southeast Kansas unearthed a prehistoric mussel shell midden associated with a probable mussel cooking site. Multiple lines of evidence indicate that the midden was created by Native Americans during the Late Archaic Period and used into the Early Woodland Period (4000 – 1000 B.P.). Over 900 relic mussel valves were identified from the mussel midden. Mussel community characteristics from this archeological site were compared with a recent sampling effort of live mussels from a nearby reach of the Verdigris River. This comparative study demonstrates that the current community composition of mussels differs from that of the prehistoric mussel midden. Four species now considered to be extirpated were found in the mussel midden and several common species differed widely in relative abundance. Measurable midden valves were significantly smaller than recent samples. Seasonal growth-rest lines of well-preserved midden shells suggest that this prehistoric harvest of mussels probably occurred in late summer.
Historical change in fish assemblage structure was evaluated in the mainstems of the Des Moines, Iowa, Cedar, Wapsipinicon, and Maquoketa rivers, in Iowa. Fish occurrence data were compared in each river between historical and recent time periods to characterize temporal changes among 126 species distributions and assess spatiotemporal patterns in faunal similarity. A resampling procedure was used to estimate species occurrences in rivers during each assessment period and changes in species occurrence were summarized. Spatiotemporal shifts in species composition were analyzed at the river and river section scale using cluster analysis, pairwise Jaccard's dissimilarities, and analysis of multivariate beta dispersion. The majority of species exhibited either increases or declines in distribution in all rivers with the exception of several “unknown” or inconclusive trends exhibited by species in the Maquoketa River. Cluster analysis identified temporal patterns of similarity among fish assemblages in the Des Moines, Cedar, and Iowa rivers within the historical and recent assessment period indicating a significant change in species composition. Prominent declines of backwater species with phytophilic spawning strategies contributed to assemblage changes occurring across river systems.
The feeding habitats of young-of-year river sturgeon Scaphirhynchus spp. from the Lower Mississippi River were evaluated. Seventy specimens collected between 2001 and 2010 (99%: 2006–2010) were dissected and gut contents analyzed. The macrohabitats and habits associated with sturgeon prey items (primarily benthic macroinvertebrates) were used to make inferences about habitat use by young-of-year river sturgeon. These findings indicate that young river sturgeon inhabiting the Lower Mississippi River feed primarily over sandy benthos, most likely in channel habitats. The majority of prey items (64.0%) consumed by young-of-year river sturgeon belong to a single subgroup of Chironomidae (Diptera: Chironominae: Harnischia complex) of which several genera, including Chernovskiia, Cryptochironomus, Gillotia, Paracladopelma, Robackia, and Saetheria, are known to be primary inhabitants of this macrohabitat.
Telemetry is valuable for understanding animal ecology and assessing conservation priorities. Sturgeon species worldwide are imperiled and telemetric methods have been applied to adults, but the feasibility of using this methodology on age-0 sturgeon remains unclear. The pallid sturgeon (Scaphirhynchus albus) is a federally endangered species in the central United States and little is known about its early life ecology. The use of telemetry on age-0 pallid sturgeon would greatly increase understanding of their early life ecology. We assessed growth, survival, and swimming performance of age-0 pallid sturgeon tagged with 0.2 g, nonfunctioning radio telemetry tags to determine whether radio telemetry can be used on such small sturgeon. Tags were surgically implanted internally and attached externally, with a control group that only experienced handling. Age-0 sturgeon with internally implanted tags grew slowly and had low survival, while counterparts within the control group and those with external tags grew faster and had almost 100% survival. No differences in critical swimming speed occurred among the internally tagged, externally tagged, and control fish. We suggest externally tagging age-0 sturgeon may be possible. However, a small telemetry transmitter that uses technology (e.g., ultrasonic) which transmits well in deep rivers while maintaining a minimum tag weight and maximizing battery life is needed.
Researchers often employ radio telemetry to locate study animals efficiently, but the time required to locate individuals can make monitoring large populations difficult and costly. In 2010–2011 we located nesting ornate box turtles (Terrapene ornata) in a large group of radio-tagged animals. To minimize search efforts, we investigated whether automated radio telemetry and the signal change method could be used to identify nesting activity before locating animals. The signal change method relies on the principle that any movement of a radio transmitter, including minor changes in orientation, can strongly affect the intensity of the transmitter's signal at a stationary receiving station. Using video recordings of free-ranging radio-tagged turtles, we confirmed that transmitter signal strength values can be analyzed to identify periods of box turtle activity. Early in the 2010 nesting season, automated telemetry observations indicated that some females engaged in nocturnal activity. Previous reports indicate that ornate box turtles often nest at night but are otherwise inactive after dark. Based upon this information and relatively little indication of nocturnal activity by males, we hypothesized that nocturnal activity corresponded to nesting. We subsequently monitored female nighttime activity in near real time, hand-tracked four night-active individuals, and found three of these turtles nesting. In 2011 we again selectively hand-tracked night-active females and located nests for 12 of 18 study animals, which approximates the expected annual reproductive rate for our population. We demonstrate that the signal change method can be used to identify nesting activity in ornate box turtles and suggest this method may be of use in other species that nest outside of their normal activity periods.
We examined Cassin's sparrow (Aimophila cassinii) territory characteristics in shrub-grassland in northwestern Oklahoma during the 2008 breeding season. We estimated Cassin's sparrow territory area using territory mapping and song playback. Additionally, we determined vegetation cover, and aspect within territories and at nonterritorial sites, at both small scale (214 ha) and large scale (4856 ha). Mean territory size was 0.55 ha. Territories were 1.8 × more likely to be on north aspects than expected. Additionally, territories had greater shrub [sand sagebrush (Artemisia filifolia)] cover than the surrounding landscape.
In the Flint Hills of Kansas and Oklahoma, U.S.A., grazing land is managed predominantly to promote homogeneous grassland structure. This potentially limits the diversity of habitats for grassland obligate songbirds with narrow habitat preferences during the breeding season, prompting ecologists and conservationists to call for managing rangelands for increased heterogeneity. The Flint Hills also hosts multiple species of conservation concern during winter, but avian habitat requirements are less well known during this period and seldom considered in management recommendations. We investigated the influence of vegetation structure on occurrence of songbirds overwintering at The Nature Conservancy's Tallgrass Prairie Preserve in Osage County, Oklahoma, where fire and grazing are used to increase structural and compositional heterogeneity. During the winters of 2008–2009 and 2009–2010, we used an area-search method to survey 149, 1 ha plots distributed among patches that represented a wide gradient in vegetation structure and 1–3 growing seasons since fire. We modeled occurrence of Le Conte's Sparrow (Ammodramus leconteii), Sedge Wren (Cistothorus platensis), Savannah Sparrow (Passerculus sandwichensis), and Smith's Longspur (Calcarius pictus) with a combination of fine-scale vegetation (e.g., litter depth in sampling plots), landscape-scale factors (e.g., distance to utility poles), and time since fire. Vegetation height was the most consistent predictor for three species, with Le Conte's Sparrow and Sedge Wren associated with tall structure and Smith's Longspur associated with shorter structure. Occurrence of Smith's Longspur was too low to adequately model effects of burn age, but fine-scale vegetation structure used by Le Conte's Sparrow and Sedge Wren was available in plots irrespective of time since fire. A variety of management techniques for creating habitat heterogeneity have the potential to promote grassland songbird diversity during winter, but further study is needed.
American badgers (Taxidea taxus) are a prairie obligate species, but badger resource selection and space use is poorly understood, particularly east of the Mississippi River where anthropogenic land uses have replaced most native prairie. We assessed badger multi-scale resource selection and space use in intensive agricultural areas in Illinois and Ohio. We predicted that badgers would select for pasture and prairie, and higher elevations, and riparian areas because these habitats likely favor burrowing and foraging. Conversely, badgers should avoid cropland, roads, and forest at both spatial scales because these habitats may limit burrowing and foraging and potentially increase mortality risk. We also predicted annual male space use would increase with age and be greater than females because of age-related dominance and polygynous mating. We used radiolocations from 18 (11 females, seven males) and five (two females, three males) badgers in Illinois and Ohio, respectively, to estimate space use and multi-spatial scale resource selection. Within study areas, badgers strongly selected for cropland and higher elevations, and a lesser extent upland forest and pasture, but avoided roads and riparian areas. Landcover selection within home ranges varied by study area, but generally, badgers strongly selected for pasture, cropland, prairie, or higher elevation. Median annual 95% fixed kernel areas of Illinois badgers were greater (W8 = 16.00, P = 0.007) for males than females, and most males appeared to overlap two to three females during the breeding season. We suggest, although our study areas were highly fragmented agricultural landscapes, badgers appeared to select land cover types similar to native prairie, which provided burrowing and foraging opportunities. However, because prairie and pasture were relatively limited, badgers used expansive (x̄ = 20.0 ± 34.4 km2) home ranges to meet life requirements. Therefore, degradation and fragmentation of limiting resources may limit badger population growth in our study areas and should be considered for future management.
Habitat use was studied for 28 deer (Odocoileus virginianus) in a suburban area 20 km northeast of the city of Philadelphia. Deer were tracked at high frequency by the use of GPS collars (one GPS fix every 5 min for weeks to months) providing high resolution location data. Habitat disturbance was ranked using several approaches. One metric was based on a human activity index (scale 0–10, with zero corresponding to least impacted and ten to most impacted habitat). A second metric was based on vegetation succession depression [scale 0–5, with zero indicating areas undergoing natural succession and five for areas where succession is almost impossible (paved roads, buildings)]. In addition habitat was classified by the density of occupied buildings. The resulting GIS model depicting habitat disturbance (Disturbance Index, DI) was then plotted against GPS fixes generated by individual deer. Monitored animals selected wooded habitat with shrubby underbrush, neglected land parcels, and fields with annual and bi-annual mowing regimes. They avoided high-density residential areas and very low disturbance areas, but tolerated areas with low density of buildings (fewer than 400 buildings km−2). Deer preferences along the suburban disturbance gradient suggested that patches of moderate disturbance with ongoing succession in areas with low building density are most important for the deer. Managing these areas could be instrumental in controlling the deer herd.
In Wisconsin white-footed mice (Peromyscus leucopus noveboracensis) and woodland deer mice (P. maniculatus gracilis) are difficult to distinguish. Recent climatic trends have facilitated encroachment of P. leucopus north into the range of P. maniculatus, necessitating unambiguous species identification as researchers begin to untangle the ecological implications of such community changes. Cranial and external measurements have been used by previous investigators to differentiate these species in other regions. However, because large geographic morphological variation occurs and most previous studies used measurements from dead specimens, definitive morphological characteristics need to be identified that can quickly and effectively classify live Wisconsin Peromyscus in the field. During the summer of 2010, we collected tissue samples and measured ear length, tail length, hindfoot length, and body weight of 84 P. maniculatus and 293 P. leucopus live-trapped in six Wisconsin counties. We used mDNA analysis to identify species. We developed discriminate function analysis (DFA) equations to identify characteristics that best distinguished species. Ear length correctly classified 97.9% of the samples with all but one P. leucopus <17 mm and all but seven P. maniculatus ≥17 mm. By adding body weight to the function, we were able to achieve 99.2% classification accuracy and with the addition of tail length were able to achieve 99.5% accuracy.
Although prescribed fires are commonly used in management, little is known about how temperatures generated during fires affect the seed viability of species of conservation concern. We measured seed viability of six herbaceous forbs native to Ozark glade ecosystems and the glade-invading shrub Juniperus virginiana (eastern redcedar) after exposure to four temperature treatments for 15 min: 24 C, 50 C, 100 C and 150 C. Viability of Allium canadense and Ruellia humilis was reduced to near zero after exposure to temperatures of 100 or 150 C, whereas viability of Echinacea simulata and J. virginiana was only significantly reduced at 150 C. Lespedeza virginica, Oenothera macrocarpa, and Silphium terebinthinaceum maintained substantial viability after exposure to 150 C, with the proportion of viable seeds ranging from 0.3–0.5. Our results suggest that interspecific differences in tolerance to heat-related mortality of seeds may be an important factor mediating post fire patterns of plant regeneration.
Carnivorous plants inhabit nutrient-poor soils and capture insects to supplement the nutrients that can be acquired from the soil. However, most carnivorous plants also utilize insect pollinators, potentially leading to a “pollinator-prey conflict.” The phenology of pitcher and flower development in Sarracenia alata was examined in order to determine whether this species might avoid pollinator-prey conflict by phenological differences in the production and activity of flowers and traps. In two sites examined in different years, the phenological patterns of flower and pitcher development were significantly different. Less than 1% of plants had flowers and pitchers active at the same time. These phenological differences in activity patterns of flowers and pitchers result in little opportunity for pollinator-prey conflict in this species but may have evolved for other reasons.
The use and potential consequence of alien plant parts in the construction of open-cup leaf nests by Nearctic-breeding forest songbirds has not been investigated. We dissected 19 leaf nests constructed by Veeries (Catharus fuscescens) over two breeding seasons in a temperate broadleaf forest infested with alien plants. Our objectives were: (1) confirm the architectural approach used by Veeries to construct nests, (2) determine if Veeries used alien plant parts in nest construction, (3) determine if nest success was related to the use of alien material, (4) determine the use of alien plants relative to native plants, and (5) test for an association of alien plant mass with the progression of the nesting season. Our results showed that Veeries constructed three separate nest layers: (1) a platform for support, (2) an inner cup, and (3) nest lining. Veeries incorporated parts from six alien plant species in their nests representing 22% of the 27 species used. All nests contained alien plant parts but use differed among the three layers. In particular the use of stems of Alliaria petiolata and Rosa multiflora, two alien species, appeared to provide important structural support in the nest's outer layers. Although our sample size was small, we found no relationship between the use of alien plant parts and nest failure suggesting use of alien plant material does not have negative effects on productivity. We caution that sudden large-scale restoration efforts, which remove the alien forest plant species used in nest construction prior to the recovery of comparable native species, may result in the temporary reduction of materials available to birds for nest construction.
American eel populations are declining and have recently become a species of interest by the United States Fish and Wildlife Service to list as a threatened species. However, the American eel population in the largest inland lotic waterway in North America (Mississippi River) has received little attention despite the apparent relevance. Because of the lack of information on the Mississippi, we evaluated trends in relative abundance and habitats occupied by American eel using long-term data collected on the Mississippi River (i.e., Upper Mississippi River Restoration – Environmental Management Program). During the 18 y study, a total of 92 American eels were collected throughout the Upper Mississippi River (Lake City, Minnesota downstream to Cape Girardeau, Missouri) with a relatively fewer individuals captured as of recent. Across macrohabitats, unstructured and structured (i.e., diked) main channel borders had the greatest number of American eels captured; however, eels were infrequently captured in impounded habitats. In terms of mesohabitat use, most American eels were captured in areas characterized by the shallowest waters, rock substrates, and low velocities. We believe the information provided in this study will promote American eel conservation in the Mississippi River.
Atypical color morphs have been described in many species of salamander, but few descriptions are quantitative, and none address those found in the Southern Red-backed Salamander, Plethodon serratus. In 2010 and 2011, we conducted 5 weekly rounds of diurnal leaf litter and natural cover object searches per season (Spring and Fall) in the Ozark Mountains of South central Missouri, U.S.A., with a total of 800 individual 3 × 3 m plots searched. We found 1876 Plethodon serratus (Southern Red-backed Salamander), 20 P. albagula (Western Slimy Salamander), and four Eurycea longicauda melanopleura (Dark-sided Salamander). Of the 1876 P. serratus encountered, all but six exhibited the red-backed phase. Atypical color morphs included the lead-backed phase (n = 2, including a gravid female), the silver-backed (grey stripe) phase (n = 1), a ghost-backed (white stripe) phase (n = 1) and the hypomelanistic phase (n = 2). The majority of salamanders were found in leaf litter, followed by woody cover and rocks. Two adults of P. serratus were encountered in burrows of cicada nymphs. We encountered only 3 of the 4 color morphs described for P. cinereus, the sister species of P. serratus, but added two color morphs to the list known for P. serratus. We expect that additional surveys for P. serratus in other parts of their range will help determine whether color morph frequency varies between populations and habitat as it does for P. cinereus.
Social organization influences carnivore demography, space use, density, and abundance. In bobcats (Lynx rufus) social organization is thought to be affected by multiple interacting factors including relatedness, sex, and prey and conspecific density. To provide baseline data on the effect of relatedness on bobcat social organization, I examined space use and overlap among two sibling, adult female bobcats in east-central Minnesota, and compared these results to previously published research. Estimated bobcat home range size was similar to that of previous studies, suggesting stability in home range size across several decades and reliability in our estimates. Home range and core area overlap was within the range of previous studies. However, the use of two different methods for estimating core area suggested that the subjective use of the 50% utilization distribution would have underestimated core area size and overlap. Although limited, these data provide the first estimates of home range and core area overlap among adult sibling bobcats.