Showing papers in "American Midland Naturalist in 2005"
TL;DR: Results indicate that C. drummondii exerts strong control over the structure and function of unburned mesic grassland ecosystems and that this shrub may be key in the conversion of grasslands to woodlands.
Abstract: The clonal shrub Cornus drummondii is rapidly displacing mesic grassland in the central U.S. due to fire suppression and changes in land use. Once established, this shrub is not readily eliminated by the return of frequent fire, leading to significant and perhaps irreversible shifts in tallgrass prairie structure and function. We assessed the impacts of C. drummondii encroachment on herbaceous aboveground net primary production (ANPP) and plant community structure in tallgrass prairie and the role this species plays in the conversion of grassland ecosystems to shrub/woodlands. We also removed established C. drummondii clones to assess the potential of the grassland ecosystem to recover after shrub dominance. Aboveground net primary production, vegetative cover and species richness and diversity (exclusive of C. drummondii) were significantly reduced beneath shrub islands relative to open grassland, with reductions in ANPP and richness of up to 94 and 45%, respectively. Forbs were the dominant growth form in the C. drummondii understory, and 10 species primarily associated with woodland habitats occurred only within shrub islands. Upon removal of C. drummondii, ANPP, richness and diversity recovered to grassland values within 2 y; however, forbs remained the dominant growth form, comprising 73% of total cover. These results indicate that C. drummondii exerts strong control over the structure and function of unburned mesic grassland ecosystems and that this shrub may be key in the conversion of grasslands to woodlands. Removal of C. drummondii resulted in some aspects of recovery, but the return of graminoid dominance was not attained after 2 y. This represents a legacy effect of C. drummondii of unknown duration. Prevention of woody species encroachment through frequent burning is a preferred management option for this ecosystem.
103 citations
72 citations
TL;DR: In this paper, the authors investigated the size of foraging areas and habitat use by red bats during summer 2000 and 2001 in an intensively managed pine landscape in east-central Mississippi, USA.
Abstract: Forest managers are increasingly expected to incorporate biodiversity objectives within forest landscapes devoted to timber production. However, reliable data on which to base management recommendations for bats within these systems are extremely limited. Although the red bat (Lasiurus borealis) is a widespread common species in temperate forests of North America, little is known of its ecology within intensively managed pine (Pinus spp.) forests of the southeastern United States. Therefore, we investigated size of foraging areas and habitat use by red bats during summer 2000 and 2001 in an intensively managed pine landscape in east-central Mississippi, USA. We captured bats using four-tier mist nets placed over water and attached radiotransmitters to red bats. Radiotagged red bats (n = 16) used habitat types randomly at the study area and foraging area scale. Mean size of foraging areas and mean maximum distance traveled between diurnal roosts and foraging locations were not different (P < 0.05) among adult male, adult female, juvenile male or juvenile females (n = 18). Most foraging areas contained a reliable source of water and all but one diurnal roost was located within foraging areas. Location of diurnal roosts may dictate location of foraging areas. Open canopy conditions in intensively managed pine stands (young, open canopy stands, thinned stands and riparian hardwood stands) likely provide appropriate foraging habitat for red bats. Landscape context may influence size of foraging areas and commuting distances of red bats. Provision of appropriate aged forest stands for diurnal roosts may be the best management action for red bats within intensively managed pine landscapes.
69 citations
TL;DR: The Mammoth Spring crayfish (Orconectes marchandi) is listed as endangered by the American Fisheries Society's Endangered Species Committee and globally impaired by the Missouri Natural Heritage Database as mentioned in this paper.
Abstract: The Mammoth Spring crayfish (Orconectes marchandi) is listed as endangered by the American Fisheries Society's Endangered Species Committee and globally impaired by the Missouri Natural Heritage Database. Recorded at only three locations in the Spring River watershed (southern Missouri and northern Arkansas), little information exists on its range, associations with other crayfish and habitat selection. We sampled stream-dwelling crayfish with kicknets and quadrat samplers during spring-summer over 2 y in the Spring River drainage to determine distribution, relative density, habitat use, species associations, and life history characteristics of O. marchandi and other associated crayfish species. Nine crayfish species were collected in the Spring River watershed including a previously unrecorded invasive species, O. neglectus chaenodactylus, that appears to have replaced the native O. eupunctus from a portion of the watershed where it was previously abundant. The known distribution of O. marchandi...
57 citations
TL;DR: The authors examined overlap in space use of sympatric Bobcats, coyotes and gray foxes in central Mississippi during 1993-1997 and found that the home ranges of all three species overlapped extensively.
Abstract: Sympatry among bobcats (Lynx rufus), coyotes (Canis latrans) and gray foxes (Urocyon cinereoargenteus) is relatively recent in the southeastern United States given recent expansion of coyote range. Interspecific relationships among canids and felids have been documented in northern latitudes. However, interactions among these three species at southern latitudes are poorly understood. We examined overlap in space use of sympatric bobcats (n = 47), coyotes (n = 37) and gray foxes (n = 27) in central Mississippi during 1993–1997. Home ranges of all three species overlapped extensively. However, gray foxes maintained core use areas that did not overlap substantially with those of bobcats and coyotes. Home range and core area overlap were similar across seasons among all species. Our findings indicate that these three species readily share space, but gray foxes apparently maintain core areas in areas void of concentrated bobcat and coyote use.
57 citations
TL;DR: In this paper, the authors evaluated seed production and carrying capacity of a 931ha wetland at Chautauqua National Wildlife Refuge in central Illinois during falls 1999-2001, and estimated carrying capacity across years was 6.760 ± 411 (se) duck use-days/ha.
Abstract: The Illinois River Valley (IRV) is a critical ecoregion for migratory waterfowl. Significant wetland loss occurred in this region in the early 20th Century, and remaining wetlands are subject to additional degradation via sedimentation, summer flooding from the Illinois River and invasive species. Managed moist-soil wetlands may provide quality foraging habitat for migrating waterfowl, but contemporary estimates of seed production and carrying capacity do not exist for the IRV. We evaluated seed production and carrying capacity of a 931-ha moist-soil wetland at Chautauqua National Wildlife Refuge in central Illinois during falls 1999–2001. Seed production varied annually (329–1231 kg/ha), but overall was greater than previously published estimates for other areas of North America. Estimated carrying capacity across years was 6.760 ± 411 (se) duck use-days/ha; this value was 1.5–15.4 times greater than other published carrying capacity estimates for harvested corn, rice and soybeans. We recommend ...
55 citations
TL;DR: It is hypothesized that interspecific amplexus with introduced R. catesbeiana could result in reproductive interference with negative demographic consequences in native ranid populations that have been reduced or altered by other stressors in western North America.
Abstract: Introduced American bullfrogs (Rana catesbeiana) come in contact with native amphibians on four continents and are well established in lowlands of western North America. To date, research on the effects of introduced bullfrogs on native frogs has focused on competition and predation, and is based largely on larval interactions. We present observations of interspecific amplexus between bullfrogs and two native ranid frogs (R. aurora and R. pretiosa) from six sites across the Pacific Northwest that imply that this interaction is more widespread than currently recognized. Our observations indicate that R. catesbeiana juveniles and subadults in this region are of appropriate size to elicit marked amplectic responses from males of both native species. Our literature review suggests that greater opportunity may exist for pairings between R. catesbeiana and native R. aurora or R. pretiosa than among syntopic native ranids in western North America. We hypothesize that interspecific amplexus with introduc...
54 citations
TL;DR: Fly maggots, numbering up to 50,000 per carcass, can consume virtually an entire salmon within 5 d, so bears as consumers and transporters of carcasses facilitate the scavenging of carcass by maggot, increasing the transfer marine-derived nutrients from aquatic to riparian habitats.
Abstract: The carcasses of Pacific salmon can be an important food resource for aquatic and terrestrial organisms, depending on where the carcasses are located. We hypothesized that the availability of sockeye salmon (Oncorhynchus nerka) carcasses to ovipositing flies (Family: Calliphoridae) would be facilitated by brown bears (Ursus arctos) moving salmon from the water to terrestrial environments. We further hypothesized that the proportion of carcasses in terrestrial environments (hence accessible to flies) would vary among streams as a function of stream size. In three small southwestern Alaska streams during 2 y, flies oviposited on about half of the carcasses in terrestrial habitats (44% of those on gravel, 54% in grass and 57% in the forest). Only 28% of the partially submerged carcasses and 0.5% of the fully submerged carcasses were colonized. The proportion of carcasses deposited outside the stream was strongly and positively influenced by the level of bear predation and negatively affected by stre...
54 citations
TL;DR: In this paper, the effects of tillage agriculture on soil quality related parameters of former tallgrass prairie were assessed to identify soil properties most impacted by cultivated agriculture and those that may be desirable to restore and providing potential restoration targets based on native soil properties.
Abstract: Soil properties were assessed to determine the effects of tillage agriculture on soil-quality-related parameters of former tallgrass prairie. Soil physical, chemical and biological properties were evaluated in the top 10 cm at six native grassland sites within the Grand Prairie region of east-central Arkansas and compared with adjacent tilled agricultural land in a total of 11 prairie-agriculture land-use combinations. Soil organic matter and total C and N concentrations were significantly lower and soil pH, electrical conductivity and extractable soil P, K, Ca, Mg, Fe were significantly higher under tilled agriculture than under native prairie land use. The introduction and continuance of intense mechanized agriculture and its associated practices have significantly, and for the most part negatively, impacted native soil quality in this region. These results will aid prairie restoration efforts by identifying soil properties most impacted by cultivated agriculture and those that may be desirable to restore and providing potential restoration targets based on native soil properties.
53 citations
TL;DR: In this paper, the authors studied turtle populations inhabiting a canal and a lake (both man-made) within a heavily disturbed, urban setting and found that G. geographica was the most common species in the canal habitat, T. scripta was most common in the lake habitat.
Abstract: We studied turtle populations inhabiting a canal and a lake (both man-made) within a heavily disturbed, urban setting. Six aquatic and semi-aquatic turtle species were collected in both habitats: spiny softshell turtle (Apolone spinifera), painted turtle (Chrysemys picta), common snapping turtle (Chelydra serpentina), common map turtle (Graptemys geographica), common musk turtle (Sternotherus odoratus) and red-eared slider (Trachemys scripta). While G. geographica was the most common species in the canal habitat, T. scripta was most common in the lake habitat. We describe patterns of sexual size dimorphism and sex ratios for the three most abundant species (G. geographica, T. scripta and S. odoratus). We discuss our data in light of problems facing turtle assemblages in urban settings.
51 citations
TL;DR: In this article, the authors consider how invasive dreissenid mussels affect ecosystem stability processes in Lake Erie through both consumptive and excretory processes using the stability landscape heuristic.
Abstract: Ecosystem stability processes such as constancy, resilience and persistence are important, but often neglected, topics of invasive species research. Here we consider how invasive dreissenid mussels affect ecosystem stability processes in Lake Erie through both consumptive and excretory processes using the stability landscape heuristic (Gunderson, 2000). Consumption of phytoplankton by dreissenid mussels adds complexity to the system and potentially slows energy transfer from lower to higher trophic levels decreasing system constancy and lowering system resiliency. Excreting soluble waste products at low nitrogen to phosphorus ratios exacerbates these impacts on stability processes because low nutrient ratios favor growth of cyanobacterial blooms, less preferred food of zooplankton, further decreasing the transfer of energy from lower to higher trophic levels. We also provide evidence for recent changes in Lake Erie's stability landscape including a return towards eutrophy.
TL;DR: In this article, the authors conducted a mark-recapture study within a 216 × 18 m stream section in east-central West Virginia using diurnal and nocturnal survey methods.
Abstract: Though locally abundant throughout the high mountains of West Virginia, intensive studies on the natural history and population structure of the hellbender, Cryptobranchus alleganiensis, have not been conducted in the state. From 1998–2000 we conducted a mark-recapture study within a 216 × 18 m stream section in east-central West Virginia using diurnal and nocturnal survey methods. Ninety-nine captures of 44 individuals were recorded. Density estimates ranged from 0.8–1.2 individuals/100 m2. The sex ratio was 1.2:1. Sexual dimorphism was apparent, as females were longer and heavier than males. However, the longest males were underweight compared to their predicted mass. This population was highly skewed toward large adults, and larvae and juveniles were not encountered. The mean inter-capture distance was 35.8 m and 95% MCP home range estimates averaged 198 m2. Water depth where hellbenders were captured ranged from 16–56 cm and individuals were never captured in heavily silted areas. Hellbender ...
TL;DR: A 3-y study examining the food habits of wolves in an agricultural area of northwestern Minnesota and their relation to depredation records of livestock losses in the same area found that wolves in the area preyed mostly on native prey species.
Abstract: Wolves (Canis lupus) have recolonized many areas of the Midwestern United States, prompting concern over the possible risk wolves may pose to livestock producers. To better understand the risks wolves may pose to livestock, we initiated a 3-y study examining the food habits of wolves in an agricultural area of northwestern Minnesota and their relation to depredation records of livestock losses in the same area. We collected 533 wolf feces during the non-winter seasons from 1997–1999. White-tailed deer (Odocoileus virginianus) was the most abundant food item (39.2%) of all prey items for all 3 y combined. The deer component comprised both adult deer (26.9%) and fawns (12.3%). Muskrats (Ondatra zibethicus) were the second highest food item at 16.6%. Moose (Alces alces), both adults (13.0%) and calves (0.6%), comprised 13.6% of the diet of wolves, followed by cattle (10.3%), domestic pig (4.4%), lagomorphs (3.6%) and beaver (Castor canadensis; 2.1%). During our 3-y study, eight head of livestock wer...
TL;DR: The results show that C. secretus can forage at much greater distances than previously reported, and should assist in the development of effective preserve design and management strategies for caves with endangered species in central Texas.
Abstract: Cave invertebrate communities are dependent upon exogenous energy sources because their environment generally lacks primary producers. In small caves of central Texas, endemic terrestrial cave invertebrates often rely in part on the energy brought into caves by cave crickets (Ceuthophilus spp.), which forage above ground at night and roost in caves during the daytime. Knowledge of cave cricket foraging range is needed to effectively protect invertebrate communities that include federally endangered species. We marked approximately 2000 C. secretus emerging from Big Red Cave (Coryell County, Texas) with UV bright paint and located 291 previously marked crickets over 17 nights. Crickets foraged up to 105 m from the cave entrance and were present in relatively uniform densities out to 80 m. While 51.1% of the crickets were found within 40 m, 8.1% were found at 80 m or beyond. Relocated crickets were predominantly found in grasses (30.7%), leaf litter (22.4%) and herbaceous vegetation (20.4%) and were found close to ground level (mean = 0.49 cm). Our results show that C. secretus can forage at much greater distances than previously reported. The new data from our study should assist in the development of effective preserve design and management strategies for caves with endangered species in central Texas.
TL;DR: The authors of as discussed by the authors studied nest-site fidelity and nest predation in a population of Chrysemys picta marginata at Miller's Marsh on Beaver Island, Michigan, and found that most turtles emerged during the mid-afternoon and nested during the evening hours.
Abstract: We studied nest-site fidelity (1995–2000) and nest predation (1997–2000), and nesting movements (1999–2000) in a population of Chrysemys picta marginata at Miller's Marsh on Beaver Island, Michigan. On average, turtles nested farther (mean = 122.3 m) from the marsh than turtles in previously studied populations, possibly because of the relatively large nesting areas (n = 5) of our study. Nest predation was 17.4% over all years and was independent of nest location (distance from water, road vs. field nests, nesting field). Many turtles showed nest-site fidelity between years in that they favored one or two nesting areas and had annual inter-nest distances (ID) that were positively skewed and significantly less (mean = 88.7 m) than IDs of randomly paired nests of different individuals. Radiotelemetry indicated that most turtles emerged during the mid-afternoon and nested during the evening hours. Nesting excursion duration averaged 11.6 h and 75% remained on land overnight after nesting. The use of...
TL;DR: Survival during dispersal was greater for beavers emigrating from lodges on the land-locked, less densely populated site than for those dispersing in an area of higher population densities, but did not differ between dispersers and non-dispersers at either site.
Abstract: We used radiotelemetry to estimate natal dispersal patterns and survival rates of 13 yearling and 19 subadult beavers (Castor canadensis) at two geomorphologically different sites in southern Illinois. Overall, we observed a 55% dispersal rate for yearlings and a 73% dispersal rate for subadults. Normally, juveniles (yearlings + subadults) initiated dispersal around 16 February (range = 28 Jan.–20 Mar.) and settled around 18 April, with juveniles remaining transient from late January through late June. Nine subadult beavers dispersed significantly earlier at one site (x = 25 Nov., range = 31 Oct.–16 Dec.), presumably due to intra-colony strife brought on by management-induced autumn flooding of wetlands for waterfowl. Dispersal occurred earlier than documented in northern regions. Beavers dispersed farther from natal colonies with free-flowing water access (x = 5.9 km) than those landlocked (x = 1.7 km). Males moved more frequently and traveled greater distances per individual move than did fe...
TL;DR: A novel quantitative approach to estimating the risk of species establishment by combining a model for population spread with known allometric correlations between body size and population growth rate for broad taxonomic categories is presented.
Abstract: Introductions of non-indigenous species in ballast water are one of the greatest threats to freshwater and marine ecosystems worldwide. New approaches to reducing the release of organisms from ballast water are under consideration nationally and internationally. Unfortunately, the development of scientifically defensible policy for controlling introductions from ballast water has been retarded by the lack of relevant ecological theory and a shortage of information about the identity and numbers of organisms in ballast. Here, we present a novel quantitative approach to estimating the risk of species establishment by combining a model for population spread with known allometric correlations between body size and population growth rate for broad taxonomic categories. Our approach is applicable to sexually reproducing, planktonic taxonomic groups including ctenophores, cnidaria, arthropods, annelids, mollusks and (as an approximation) echinoderms and fishes. As expected, the allowable volume of balla...
TL;DR: In this article, the authors monitored 12 coyotes (Canis latrans) in northwestern Texas to determine their home ranges and habitat use in a landscape interspersed with native prairie, farmland and Conservation Reserve Program (CRP) fields.
Abstract: From 1999 to 2001 we monitored 12 coyotes (Canis latrans) in northwestern Texas to determine their home ranges and habitat use in a landscape interspersed with native prairie, farmland and Conservation Reserve Program (CRP) fields. Annual home range size was 10.1 km2 for residents and 84.5 km2 for transients. We determined habitat use at two spatial scales: within home ranges and within study area. Habitat use patterns were similar at both scales, as residents selected for native prairie and transients selected for CRP fields. Habitat use between residents and transients differed in both seasons, with residents selecting more native prairie, less farmland and less CRP (summer only) than transients. Habitat at natal den sites also differed from expected for residents, as most dens (8 of 10) were located in CRP fields. The CRP fields contained the only tall permanent vegetation on our study sites and appeared to provide important foraging habitat for transient coyotes, and denning habitat for resid...
TL;DR: It is suggested that toad tadpoles have not evolved active cannibalism because of energetic and other costs and because mortality rates of tadpole are naturally high in shallow ephemeral breeding ponds, which means living tadPoles thus have access to dead tadpols as a food source in such circumstances without incurring some costs of cannibalism.
Abstract: We performed two experiments to address the questions of whether toad tadpoles (Bufo a. americanus): (1) gain an advantage from consuming conspecifics and (2) engage in active cannibalism as opposed to scavenging. Our results show that tadpoles fed algal mats (and associated debris found within them) from their natal pond and supplemented on the bodies of dead tadpoles for 28 d attained an average of 5 more stages of development than tadpoles fed only on algal mats, which suggests a strong advantage to eating conspecifics. No tadpoles fed algal mats died, which suggests that this is an adequate food source. In a series of trials used to address the second question, we found no indication that tadpoles engage in active cannibalism. We tested this under conditions of hunger and using injured tadpoles as potential prey and progressively older tadpoles as potential cannibals. In no cases did we observe any tadpole attacking living tadpoles (even if injured) within 1-h after being placed in experimental tanks. Although some tadpoles were missing from tanks after 3-d periods, our results suggest that some (e.g., injured) tadpoles may succumb and are eaten thereafter. Test tadpoles began consuming dead crushed tadpoles significantly more quickly than dead intact tadpoles, suggesting that cues used to induce feeding are chemical and perhaps a result of some bacterial decomposition. We suggest that toad tadpoles have not evolved active cannibalism because of energetic and other costs and because mortality rates of tadpoles are naturally high in shallow ephemeral breeding ponds. Living tadpoles thus have access to dead tadpoles as a food source in such circumstances without incurring some costs of cannibalism.
TL;DR: It is found that juveniles from juvenile patches have a higher probability of survival than juveniles from mixed patches and adult removal improved juvenile survival in mixed patches, and the spatial and temporal segregation of juvenile and adult age classes is maintained by intraspecific competition.
Abstract: Garlic mustard (Alliaria petiolata) is an invasive, spring-germinating, obligately biennial plant. In a central Pennsylvania forest, two distinctive plant patch types exist simultaneously: patches with mixed juveniles and adults and patches that are exclusively juvenile. We experimentally tested two hypotheses to explain this peculiar distribution. The habitat limitation hypothesis proposes that garlic mustard, like other biennials, is limited to rarely available habitats and can only reach maturity in a subset of the patches where its seeds germinate. The intraspecific competition hypothesis proposes that juveniles only survive to maturity in patches lacking adults. We mapped the natural distribution of ten juvenile and ten mature patches and used transects to assess juvenile and adult density in 2 y. We found that patches cycled annually from juvenile to mixed, supporting the intraspecific competition hypothesis. We looked for biotic (interspecific competition) and abiotic (shading) factors tha...
TL;DR: C Cavity-roosting species of bats generally require patches of forest containing older timber, but such habitats have been reduced in the southeastern United States, and C. rafinesquii showed roost fidelity to particular areas of forest.
Abstract: Cavity-roosting species of bats generally require patches of forest containing older timber, but such habitats have been reduced in the southeastern United States. Rafinesque's big-eared bat, Corynorhinus rafinesquii, is a rare species for which data on natural roosts in the Gulf Coastal Plain (where caves are largely absent) are scant. We used radiotelemetry to locate tree roosts of C. rafinesquii in southeastern Mississippi from August 2001 until August 2004. We captured and radiotagged 25 bats that led us to 14 trees. Corynorhinus rafinesquii used hollow Nyssa spp. and Magnolia grandiflora. Most of these trees were still alive, relatively large (mean DBH = 79.4 cm, mean height = 18.5 m), possessed cavities with openings not located at their bases and were located adjacent to streams or other bodies of water. When bats shifted roosts among different trees, these sites were usually located nearby (mean distance ≅ 360 m). Tree roosts were apparently rare within the study area, and C. rafinesquii showed roost fidelity to particular areas of forest. Six tree roosts were used by multiple individuals and several trees were reused within tracking sessions and among years.
TL;DR: Overall, results for P. sedentarius indicate that females are faster than males, autotomy significantly reduces sprint speed in the lab for both sexes and reductions in male sprint speedIn the lab may result from a combination of autotomy and aging effects, while decreases in female speed are likely due primarily to autotomy.
Abstract: Leg autotomy in spiders is a relatively common occurrence, usually resulting from agonistic interactions with predators or conspecifics. While autotomy has immediate benefits, due to enhanced survival probability, it also potentially decreases future fitness. One possible cost of losing a leg is a reduction in burst running speed, which may affect prey capture and predator avoidance behaviors in wandering spiders. We examined sprint speed in intact and autotomized males and females of the wolf spider Pirata sedentarius from two stream banks in New York in an effort to determine if the sexes differed in either sprint speed or the potential cost of leg loss. Autotomy was fairly common in the field, with 18–22% of spiders missing at least one leg at our two sites. Males and females did not differ in frequency of leg loss. Females were larger than males (both in terms of mass and structural size) and ran significantly faster both before and after autotomy. Sprint speed was uncorrelated with body size...
TL;DR: A significant increase in length of time at sea was observed during the first 4 mo of lactation and milk ingestion and field metabolic rates established a baseline for the energetics of 1 mo old pups.
Abstract: The Cape fur seal (Arctocephalus pusillus pusillus) is a common pinniped species along the southern African coastline. While much information is available about this species, little is known concerning its reproductive energetics. With radio telemetry, we monitored attendance patterns for 1 to 4 mo from 1996–1999. Attendance of 29 nursing females averaged 1.86 ± 0.77 d on shore and 5.23 ± 2.87 d at sea. Mean cycle time was 7.09 ± 4.33 d, of which 29.6% was spent on shore and 70.4% at sea. A significant increase in length of time at sea was observed during the first 4 mo of lactation. Reproductive condition was quantified using measures of body condition and milk composition. Milk ingestion and field metabolic rates established a baseline for the energetics of 1 mo old pups. Body composition averaged 11.05 ± 2.31% lipid and 19.15 ± 2.60% protein. Milk from 17 individuals was composed of 58.07 ± 6.79% water, 2.02 ± 0.58% ash, 10.76 ± 1.23% protein and 23.16 ± 8.24% lipid. Milk energy content averag...
TL;DR: The importance of salt marsh insects as a food source to fish and birds, particularly during breeding and nesting seasons in the spring (June) or migratory season in the fall (September), is suggested.
Abstract: Adult insects were collected using emergence traps from salt water pools, brackish water pools and vegetated marsh in the Little River Estuary, Wells, Maine, USA. Samples were continuously taken once every week from June through October of 2001 to examine the community composition, as well as the spatial and temporal patterns of insect emergence from a salt marsh system. Chironomus sp. and Tanytarsus spp. (Diptera: Chironomidae) chironomids were the most abundant insects emerging, the former representing 87% of all insects collected from brackish pools and the latter 55–80% of all insects collected from salt water pools and the vegetated marsh, respectively. Insect emergence was higher from brackish pools (1450 ± 172 individuals·m−2·y−1) and vegetated marsh sites (1350 ± 851 individuals·m−2·y−1), but not significantly different from salt water pools (289 ± 126 individuals·m−2·y−1). Emergence of some species was restricted to certain marsh areas resulting in non-significant trends in patterns of c...
TL;DR: It is suggested that spring emergence may be correlated with a more complex set of factors and that Terrapene ornata ornata can withstand prolonged freezing temperatures.
Abstract: The carapace temperatures of ornate box turtles (Terrapene ornata ornata) were monitored by affixing temperature dataloggers during two winters, 2001–2002 and 2003–2004. The dataloggers recorded temperature every 3 h to the nearest 0.5 C. Date of burrowing in the fall, emergence time in the spring and temperatures 48 h prior to emergence were analyzed along with the entire temperature profile of the turtles during the winter. In 2003–2004 soil temperatures from the surface to 0.75 m depth were also monitored. Most turtles did not experience freezing temperatures during either winter, but two turtles were below freezing for up to 54 consecutive days during winter 2001–2002. During 2001–2002, eight of nine turtles began burrowing within 7 d of each other in the fall, and all nine emerged within 7 d of each other in the spring. During 2003–2004, fall burrowing for 16 turtles occurred within 14–21 d, and emergence happened within 15 d. Overwintering periods varied between 172–201 d, which was interme...
TL;DR: Winter weather reduces the availability of certain prey items in this region and may decrease the bobcat's ability to travel and hunt effectively, and sexual differences in diet may be related to sexual dimorphism in this species.
Abstract: Diet of the bobcat (Lynx rufus) in the mid-Atlantic region of the United States is poorly known. Age, sex and time of year are thought to influence bobcat prey selection, but accounts vary. We examined the contents of 85 bobcat stomachs taken from Pennsylvania during autumn and winter 2000–2002. White-tailed deer (Odocoileus virginianus) and rabbits (Sylvilagus sp.) occurred most frequently as prey. A larger percentage of female bobcats consumed lagomorphs (28%) than did males (12%; P = 0.04). More male bobcats consumed meso-mammals (14%), including raccoons and porcupines, than did females (2%; P = 0.04). Diet did not differ between bobcats <2 y and bobcats ≥2 y. Variety of prey eaten was larger in autumn than in winter. Sexual differences in diet may be related to sexual dimorphism in this species and may help to effect interspecific niche partitioning. Winter weather reduces the availability of certain prey items in this region and may decrease the bobcat's ability to travel and hunt effectively.
TL;DR: In this article, the edaphic factors affecting the distribution and potential for establishment of new populations of Platanthera leucophaea were analyzed across the range of habitats occupied by this species.
Abstract: The Federal threatened eastern prairie fringed orchid (Platanthera leucophaea) occupies prairies, sedge meadows, bogs and fens, primarily north of the Wisconsinan glacial boundary. In the Midwest, where restoration is a recovery objective, its southern distribution is thought to be limited by the transition from nutrient-rich Wisconsinan-aged soils to more acidic nutrient poor soils of Illinoian-aged glacial drift. To better understand edaphic factors affecting its distribution and potential for establishment of new populations, we analyzed soil characteristics across the range of habitats occupied by this species, as well as from unoccupied habitats on the Illinoian Till Plain. We found that P. leucophaea occupies a complex edaphic gradient in variation of % organic matter, base content and soil texture. On Wisconsinan-aged substrates, it occurs in circum-neutral base-rich organic prairie soils in Illinois and Wisconsin and in less calcareous soils with slightly higher pH and lower organic matter content in Michigan lake plain prairies. Eastern sand prairie and sedge meadow habitats on Wisconsinan-aged drift and on unglaciated soils are moderately acid and nutrient poor, while bog and fen habitats are more strongly acidic and highly organic, with no evidence for an underlying calcareous substrate. In comparison, unoccupied prairie soils on the Illinoian till plain have lower pH, % organic matter and base concentrations. These soils also have relatively high % silt content which results in comparatively low available soil moisture holding capacity. This combination of soil conditions may exceed the tolerance limits of P. leucophaea and prevent this species from occurring south of the Wisconsin glacial boundary in the Midwest. On the other extreme, calcareous fens have high pH levels as well as extremely high calcium concentrations, which may exceed the tolerance limits of this species. These findings have implications for guiding efforts to establish P. leucophaea into habitats that should be suitable for this species.
TL;DR: The role of the gopher tortoise as a generalist herbivore and an opportunistic frugivore was confirmed and some kinds of leaves were less prevalent in scats than predicted by their availability near active tortoise burrows.
Abstract: This study documents the ingestion of leaves and seeds by gopher tortoises (Gopherus polyphemus) in a relatively intact pine savanna habitat. Fifty-three species of seeds were identified. Species richness of seeds ingested was highest during spring and fall and was lowest during summer. Grass seed and foliage were consumed consistently by tortoises throughout the year. Despite being found in only 12% of all scats, Rubus seed comprised half of all seeds recovered. Based on seeds in scats, tortoises ingested the fruits of plants in the same proportions in which the plants occurred immediately around active burrows. Although some kinds of leaves were less prevalent in scats than predicted by their availability near active tortoise burrows, this may have occurred because these leaves were digested and, therefore unrecognizable in scats. The role of the gopher tortoise as a generalist herbivore and an opportunistic frugivore was confirmed.
TL;DR: These Rock Refugia Gardens demonstrate the pervasive and deleterious impact that deer are having on plant species diversity and forest regeneration in the Allegheny National Forest and likely elsewhere in the eastern US where these vertebrates are abundant.
Abstract: We surveyed the vegetation growing on the surface of tall boulders (>1.5 m), on the surface of short boulders (<0.5 m) and in areas adjacent to these boulders on the soil surface in the Allegheny National Forest, Pennsylvania. Our purpose was to test the hypothesis that tall boulders serve as refugia from deer browsing for both woody plant species as well as understory herbs. We conducted our surveys during spring when many of these herbs reproduce sexually and their inflorescences are vulnerable to browsing. Deer cannot gain access and browse on these tall boulders, whereas they can easily browse plant species on shorter boulders and on the forest floor. We predicted that the tall boulders would have the highest plant diversity, woody species density and the density of reproductive individuals of understory herbs. We found a total of more than 1300 reproductive individuals of flowering herbs of more than 10 species growing on tall boulders and only 6 reproductive individuals of only a few species growing on the soil surface. Overall, there was a much greater density and diversity of woody species and sexually reproducing herbs on tall boulders or Rock Refugia Gardens than either on short boulders or the soil surface. Because the diversity and abundance of vegetation on the short boulders was nearly identical to that on the forest floor, our findings are unlikely to be explained by tall boulders providing a superior edaphic or abiotic habitat relative to habitats on the forest floor. Species accumulation curves showed that plant species continued to accrue with area on tall boulders, but did not increase with area on the forest floor or on the short boulders. These Rock Refugia Gardens demonstrate the pervasive and deleterious impact that deer are having on plant species diversity and forest regeneration in the Allegheny National Forest and likely elsewhere in the eastern US where these vertebrates are abundant.
TL;DR: In seeds subjected to a winter → spring → summer → autumn temperature regime in controlled environments, radicles emerged in autumn in the 20/10 → 15/6 C portions of the sequence, thus, in nature, the cold winter season has no effect on dormancy-break.
Abstract: Seeds (true seed plus endocarp) of Viburnum acerifolium have underdeveloped linear embryos and deep simple epicotyl morphophysiological dormancy. Seeds mature and are dispersed in autumn, and radicles and epicotyls emerge the following autumn and late autumn-winter, respectively. Embryos in seeds incubated at 25/15 C became fully elongated in 16 wk, whereas those incubated at 5 C hardly grew at all. The optimum continuous temperature regime for both rate and percentage of radicle emergence was 25/15 C. At this regime, however, ≥20 wk were required for radicles to emerge in a high percentage of the seeds. GA3 had little or no effect on radicle emergence. In seeds subjected to a winter → spring → summer → autumn temperature regime in controlled environments, radicles emerged in autumn in the 20/10 → 15/6 C portions of the sequence. In those subjected only to the summer → autumn portions of the sequence, radicles also emerged in autumn at 20/10 → 15/6 C. Thus, in nature, the cold winter season has n...