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Residential development has been associated with habitat fragmentation and loss and declining diversity of indigenous species, especially when development occurs in ecologically sensitive environments such as wetlands and/or riparian zones. In recent decades, the upper mid-west region of the United States has experienced a dramatic increase in residential development along lakeshores. In northern Wisconsin, recent studies have documented negative effects of such development on local flora and certain fauna (avian and amphibian communities) but less is known about how mammal communities, especially carnivores, respond to housing development. To quantify the influence of lakeshore development on these taxa, we conducted snow track surveys on 10 pairs of low- and high-development lakes and deployed remote cameras at four lakes in Vilas County, Wisconsin, in 2008. Our results suggest that a higher diversity of carnivores (P = 0.006) were present on low-development lakes. Coyotes (Canis latrans) were detected most frequently (n = 34) especially on low-development lakes. Fishers (Martes pennanti), wolves (Canis lupus), bobcats (Lynx rufus), and northern river otters (Lontra canadensis) were exclusively detected on low-development lakes by snow track surveys. Raccoon (Procyon lotor) and red fox (Vulpus vulpus) detection was greater on higher-development lakes than low-development lakes. These results also were supported by 12 remote cameras on a subset of four lakes. We also investigated the influence of housing and road density in the surrounding landscape (500 m buffer) on carnivore community composition by means of a non-metric multidimensional scaling ordination. Significant associations were observed between community composition and landscape attributes associated with development. Our results suggest that residential development along lakeshores is having a negative impact on carnivore diversity in this region.
We estimated survival, examined habitat factors that affect home range size, and estimated colony reproduction for beavers (Castor canadensis) radio-tagged in east-central Illinois, an intensively farmed region. We monitored 42 radio-tagged beavers occupying the Embarras River and its tributaries from Sept. 2004 through Aug. 2006. Trapper harvest and disease contributed equally to low survival in 2004–2005 (0.29 ± 0.08), but had a lower impact in 2005–2006, resulting in higher survival (0.59 ± 0.13). Linear home ranges were longer for beavers in the river (50% = 1.2 km; 95% = 3.6 km) than for those in streams (50% = 0.7 km; 95% = 1.8 km). Distance of the den to crop fields, stem density of least preferred woody species, and water fluctuations around dens were positively correlated with home range size. Two colonies on the main river produced 59% of the kits observed from 13 colonies. Food does not appear limited in the region; however, the distribution of food resources and extreme fluctuations in stream flow likely influence beaver movements and colony dynamics.
American beavers (Castor canadensis) forage on various aquatic and terrestrial plant species. We used stable isotope analysis of carbon (C) and nitrogen (N) to estimate source contributions of seasonal assimilated beaver diets in Voyageurs National Park, Minnesota, from Apr. 2007 to Nov. 2008. Mean (±95% confidence interval) annual beaver diets were estimated as 45.5 ± 11.4% terrestrial and 55.5% aquatic vegetation (22.0 ± 14.5 emergent and 33.5 ± 7.9 floating leaf). Percentages of floating leaf and terrestrial vegetation were similar between winter and summer assimilated diets, but emergent vegetation increased 45% in summer. Although δ15N was 7% greater in summer, δ15N and δ13C were similar by age class and sex, as were assimilated percentages of emergent, floating leaf or terrestrial vegetation. Variation in total assimilated aquatic vegetation did not affect subadult and adult seasonal changes in body mass, tail thickness or tail area, but kit body condition was negatively related to total assimilated aquatic vegetation. Aquatic vegetation accounted for more assimilated diet during winter than previously reported.
Rafinesque's big-eared bats (Corynorhinus rafinesquii; RBEB) and southeastern myotis (Myotis austroriparius; SEM) are species of concern whose current population statuses are unknown. Bottomland hardwood forests are important roosting habitat for RBEB and SEM; however, ≥80% of these forests have been cleared or degraded in Mississippi. Limited information on roost site requirements exists across either species ranges; therefore, we conducted roost surveys for RBEB and SEM in bottomland and riparian hardwood forests on Noxubee National Wildlife Refuge, Legion State Park, and Tombigbee National Forest, Mississippi, during winter 2009–2010 and spring 2010. To compare seasonal roost selection for each species we compared tree species, used 95% confidence intervals (CIs) for three tree variables [diameter at breast height (DBH), cavity volume, and opening area] and logistic regression for four landscape variables (elevation, slope, distance to nearest stream, and distance to nearest road). We used Akaike's Information Criteria corrected for small sample size and model averaging to incorporate model selection uncertainty into parameter estimates of landscape models. Based on 95% CIs, RBEB and SEM in winter used trees with greater DBH and SEM used trees with larger cavities. However, during spring, RBEB and SEM occupied trees with comparable DBH and cavity size to unoccupied trees. At the landscape scale, RBEB used roost trees at lower elevations during winter and spring. During spring, SEM used trees further from roads (Importance weight = 0.76) at lower elevations (Importance weight = 0.29) and with less slope (Importance weight = 0.25). Understanding seasonal roost site selection will improve our ability to protect habitat to ensure viable populations of these bat species.
A common error in many studies is that a species may go undetected when they are actually present, thus leading to underestimates of the true population. Because imperfect detection can affect population estimates, we calculated detection probabilities of two rare bat species, Rafinesque's big-eared bats (Corynorhinus rafinesquii; RBEB) and southeastern myotis (Myotis austroriparius; SEM), when roosting in tree cavities. We used two methods: repeated surveys of the same tree cavity and a removal method where a tree cavity was eliminated from future surveys after a bat was detected. When repeated surveys were conducted, detection probabilities were 95% for each observer and 100% for two observers combined (n = 43). Using the removal method, each observer independently detected bats in tree cavities in 92% of inspections; whereas, combined observations of two surveyors improved detection probability to 99% (n = 27). We also evaluated count error for species identification and abundance using a two-observer method and compared it to digital infra-red imagery. Count errors were typically <4% and 38% when ≤20 bats and >20 bats were present, respectively, compared to digital images. When count errors occurred, most (64–73%) underestimated the number of bats present. Observers correctly identified species on 91% of occasions. Video recording tree cavities improved estimates of bat abundance and verified species composition. Repeated surveys and the removal method were similarly effective and suitable techniques for monitoring bat species occurrence; however, visual surveys were accurate for estimating abundance when number of bats was ≤20.
The manner in which animals balance their foraging needs with predation risk can inform effective management and conservation possibilities by illuminating the species' natural history. The purpose of this study was to determine whether porcupines (Erethizon dorsatum) and snowshoe hares (Lepus americanus) demonstrated a stronger response to perceived danger posed by a specialist predator (fisher, Martes pennanti) compared to a generalist predator (coyote, Canis latrans). Pairs of wooden stakes soaked in brine were placed in the wooded habitats at the University of Notre Dame Environmental Research Center, located on the border between Wisconsin and Michigan. Each pair consisted of a stake treated with scent (fisher scent or coyote urine) and a control stake that was untreated. Both prey species combined showed a preference for stakes without scent, with porcupines consuming more than hares. In addition, there was a significant interaction between scent and prey species. Porcupines showed a stronger response to fishers than coyotes, whereas hares did not show a differential response to either scent. This is consistent with the fisher's efficient method of killing and consuming porcupines, and the inclusion of hares in the diets of many predator species. Differences between porcupine and hare consumption of stakes is consistent with the foraging and defense styles of both animals.
The nine-banded armadillo (Dasypus novemcinctus), invasive to Florida and Georgia, is thought to be an important predator of nesting vertebrate species in some areas; yet little is known about how armadillos find these nests and how often depredations occur in areas with low nest densities. To quantify the armadillo's attraction to nests of two species of conservation concern, northern bobwhite quail (Colinus virginianus) and gopher tortoise (Gopherus polyphemus), and to evaluate if armadillos are more attracted to cues from prior depredation than to cues from intact nests, we conducted experiments with both captive and wild armadillos. Our results indicate that armadillos did not use cues from prior depredations to find nests; nor did they exhibit a strong attraction to eggs overall. Our results suggest that armadillos are unlikely to alter the demographics of gopher tortoises or bobwhite quail within habitats of low nest density.
This study addresses habitat differences of two sympatric turtle species, alligator snapping turtles (Macrochelys temminckii) and eastern snapping turtles (Chelydra serpentina) in six watersheds in southeastern Missouri. We found that alligator snapping turtle presence corresponded with higher abundance of submerged physical structures in the stream, deeper water, relatively higher levels of detritus, and warmer water temperatures. Greater amount of aquatic vegetation was important in characterizing eastern snapping turtle presence in traps. Eastern snapping turtles and alligator snapping turtles did not use the same areas spatially at either a microhabitat or macrohabitat scale, and were only trapped at the same location once in 282 trap locations. Future conservation plans for the alligator snapping turtle and eastern snapping turtle should consider the microhabitat characteristics of sites used by these turtles.
The persistence of a population of ectothermic vertebrates can be closely tied to variations in weather patterns that influence diel or seasonal cycling of temperature and moisture levels. We studied the effects of drought and weather patterns on the summer activity and movements of Spotted Turtles (Clemmys guttata) in a small wetland in southwestern Michigan over 2 y. During the periods of time with standing water, turtles aquatically active in depressions or terrestrial in grass-sedge-rush and Sphagnum hummocks but their movements were unaffected by daily weather patterns. Turtles tended to occupy multiple core areas within a relatively contiguous home range. When the wetland dried, turtles estivated beneath vegetation, or estivated or maintained limited activity in small forest ponds immediately adjacent to the wetland. In 2006, turtles resumed activity following heavy rains during late Jul. and early Aug. In 2007, however, late summer rains were not sufficient to restore substantial standing water in the wetland and so turtle movements were relatively low. Home range and core area size were significantly smaller in 2007 than in 2006, apparently because of the relatively short summer hydroperiod that occurred during 2007. Unlike previously studied C. guttata populations, the turtles of our population did not travel among multiple upland and lowland habitats, perhaps because such environments were not of higher quality than our wetland, or because the risks of traveling to them were too great.
Understanding space-use patterns of freshwater turtle hatchlings is critical to guide conservation efforts, yet little is known because of the difficulties in studying this early life-history stage. We investigated post-emergence movements and habitat associations of western pond turtles (Actinemys marmorata) at two study sites in western Oregon using micro-transmitters and harmonic radar methods. Hatchlings delayed emergence until spring, with few exceptions. Hatchlings typically remained within 2 m of nests for as long as 59 d after initial emergence. During migration from their nests to aquatic habitat, hatchlings embedded themselves in soil for up to 22 d at stop-over sites. Movements between successive stop-over sites averaged 27 m. Although the number of days turtles remained within 2 m of their nest following emergence varied widely among and within nests, hatchlings entered aquatic habitat relatively synchronously. Hatchlings entered aquatic habitat on average 49 d after initial emergence, and traveled an average of 89 m from their nest site. Hatchlings detected in water were always within 1 m of shore and in areas with dense submerged vegetation and woody debris. Because of delayed emergence and extended post-emergent use of the area adjacent to nests, managers must consider the trade-offs of managing vegetation for nest habitat and the potential harm to hatchlings by vegetation management near nests.
Freshwater mussels are a highly imperiled group of organisms. Understanding their demography and population dynamics is central to their conservation. We used mark-recapture techniques over a 5-year period to estimate the survival and population growth of two populations of Lampsilis radiata luteola in Ohio Brush Creek, Ohio, USA. Of particular interest was determining temporal variability in survivorship and if there were intermittent pulses in recruitment that could be capable of sustaining populations over the long term. We made 540 captures of 171 individuals at an upstream site and 104 captures of 55 individuals at a second, downstream site. Fitting mark recapture data to survival models indicated that the apparent survival rates of adults was best fit by a temporally constant parameter at both sites. At both sites apparent survival was low in comparison to published values for other freshwater mussels and estimates of survival for L. r. luteola. The yearly survival rate was higher for males (0.576; 95% C.I. 0.483–0.660) than for females (0.4851; 0.391–0.572) at the upstream site, but not at the downstream site (0.570; 0.415–0.699, estimate for sexes combined). Incorporating survival estimates into population growth models indicated that recruitment was low and relatively constant over the 5 y (2005–2009) for both populations. Size distribution data show similar, low recruitment. During this study both populations have been slowly declining in abundance due to high mortality and low recruitment.
Morphological variation of taxa frequently is correlated with local environmental variation. We tested for covariation in morphology and environmental variables in bluntnose minnow Pimephales notatus from 10 sites in central Indiana. We used principal components analysis (PCA) to summarize local environmental variation and geomorphic morphometrics (procrustes method and relative warp analysis) to summarize morphological variation among individuals. We used MANCOVA to test for variation in morphology attributable to environmental variation, body size, and sexual dimorphism. Additionally, we used linear discriminant analysis (LDA) to identify if morphology varies with sexual dimorphism. Individual relative warp scores were separated by sex and tested for covariation with habitat PC axes using Pearson's correlations. We identified shape variation that was correlated with environment irrespective of body size or sex. Individuals with deeper-bodies tended to occur in deeper and wider streams with increased discharge. Individuals with fusiform body shape (e.g., slender elongated snouts) tended to occur at sites with increased current velocity. Although the morphology of male and female individuals covaried similarly with environmental variation, LDA significantly distinguished females, which had distended abdomens, narrower caudal peduncle and dorsal fin bases, and slightly upturned head shapes compared to males. We suggest that shape variation may be a product of phenotypic plasticity and may contribute toward the success of species with broad physicochemical tolerances by enhancing their ability to occupy a wide range of hydrological conditions.
Developing a conservation plan for threatened plant species requires a solid understanding of seed germination ecology. The aims of this study were: (1) to discover the requirements for embryo growth, dormancy breaking, and germination; and (2) to determine the effect of seed age on embryo growth and germination of Narcissus alcaracensis (Amaryllidaceae), an endangered Mediterranean daffodil endemic to southern Iberian Peninsula. The phenologies of germination and embryo growth were studied in natural conditions. Temperature requirements for embryo growth and germination, and the effect of gibberellic acid (GA3) on germination were determined by incubating seeds under controlled laboratory conditions. In natural conditions, embryo growth starts in late autumn. Seedlings emerge in late winter shortly after the embryos reach a critical length of 3.3 mm, quite longer than the initial embryo length at dispersal (1.42 mm). In the laboratory, embryo growth occurs during a prolonged incubation period at 5 C. Stratification at 5 C breaks the physiological and morphological dormancy, enabling seeds to germinate at a wide range of temperatures. Cold stratification at alternating day/night temperatures of 9/5 C or constant day/night temperatures of 10 C also promoted germination. The velocity of embryo growth and germination percentages increased with seed age. Seeds of N. alcaracensis show intermediate complex morphophysiological dormancy (MPD). This is the first time that this level of MPD was detected in Narcissus, and the second one reporting an increase of embryo-growth velocity with seed age in morphophysiologically dormant seeds.
Invasive plants threaten biodiversity and impact natural ecosystems through both well-studied direct effects and lesser known indirect effects. We examined one indirect effect: whether the presence of an invasive exotic shrub, Lonicera maackii, changes seed predation of native shrub species by providing dense cover that might harbor shared seed predators (i.e., apparent competition). Our study quantified removal of seeds of exotic L. maackii and native plant species by granivores in invaded and uninvaded plots during winter and spring trials. We found that the presence of L. maackii did not change removal of native seeds in either season and that rodent granivores contributed significantly to seed removal compared to arthropods. Removal of L. maackii seeds by rodent seed predators was significantly greater than the native species studied in the spring (Cornus drummondii), suggesting that rodents may have negative effects on L. maackii in some ecological contexts by consuming seeds. Our findings highlight the need for future research to understand the context-specific mechanisms that determine the nature and strength of indirect effects in biological invasions.
The invasive forest pest, Agrilus planipennis (emerald ash borer, Coleoptera: Buprestidae), has caused significant mortality of ash (Fraxinus spp.) in southeastern Michigan, USA, where this pest is thought to have been originally introduced into North America. Phloem feeding by A. planipennis larvae leads to girdling of the host tree, which has resulted in the death of millions of ash trees in invaded landscapes. A survey of ash over a large geographic area was used to estimate numbers of dead and infested ash at a landscape scale within Indiana, Michigan and Ohio. Over 50 million ash trees infested with A. planipennis were estimated in the study area. This represented less than 20% of the ash trees at this broad landscape scale. We used an aerial survey with digital sketchmapping to identify individual and clusters of ash trees that were potentially alive in Oakland and Wayne Counties, Michigan, where A. planipennis is believed to have been active the longest. Diameters at breast height (DBH) and bark roughness were compared between live trees and the closest dead tree. Over 200 live trees were identified within five Huron-Clinton Metroparks, with 65% of these expressing signs and symptoms of A. planipennis attack. Trees that had succumbed to A. planipennis attack had significantly rougher bark than those trees that had survived, while DBH did not differ between the two groups. The probability of ash mortality increased with increasing bark roughness. Bark roughness provides insight into the potential survival of ash within forests. This case-control study, in addition to the estimates of infestation, establishes a baseline and the need to identify further individual and environmental characteristics that facilitate ash survival in the presence of A. planipennis.
Oak (Quercus spp.) savannas are among the most imperiled ecosystems in the United States. Consequently, associated vegetation and avian communities are also in decline. Furthermore, restoration of savanna communities may be an important strategy for conserving avian species that require early successional habitat, a type underrepresented on regional landscapes. Therefore, we evaluated savanna restoration on twelve sites in the Mid-South USA. Specifically, we examined grass, forb, legume, and woody understory cover, regeneration and sapling density, and breeding bird use of the sites following mechanical overstory thinning and dormant-season fire using a hierarchical linear model. Total grass cover was negatively related to canopy cover (P < 0.01) and total forb cover was negatively related to total basal area (P = 0.04). Oak regeneration density was positively related to canopy cover (P < 0.01), while oak competitor regeneration density was positively related to percent slope (P = 0.01) and sapling density (P = 0.01). Shrub/scrub birds were common within sites undergoing restoration. Only three obligate grassland bird species, eastern kingbird (Tyrannus tyrannus), Bachman's sparrow (Aimophila aestivalis) and dickcissel (Spiza americana), were detected on one site. Presence of indigo buntings (Passerina cyanea) was positively related to groundlayer development. Canopy reduction and burns outside the dormant season may both be critical to restoration of savannas and associated avifauna in the region.
Food-value theory states that territorial animals space themselves such that each territory contains adequate food for rearing young. The ovenbird (Seiurus aurocapilla) is often cited as a species for which this hypothesis is supported because ovenbird territory size is inversely related to ground-invertebrate abundance within territories. However, little is known about juvenile ovenbird diet and whether food availability is accurately assessed using ground-sampling methods. We examined the relationship between ground-litter food availability and juvenile ovenbird diet in mixed northern hardwood-coniferous forests of north-central Minnesota. We sampled food availability with pitfall traps and litter samples, and concurrently sampled diet of juvenile ovenbirds from stomach samples. We found that juvenile ovenbirds were fed selectively from available food resources. In addition, we found that both ground-sampling methods greatly under-sampled forest caterpillars and snails, which together comprised 63% of juvenile ovenbird diet by mass. Combined with recent radio-telemetry findings that spot-mapping methods can poorly estimate territory size for forest songbirds, our results suggest that comparisons of spot-mapped ovenbird territories with ground-sampled invertebrate availability may not be reliable tests of food-value theory.
Because of the importance of wetlands and because birds in urban and suburban wetlands are not well studied in relation to adjacent land cover, we estimated bird metrics within six suburban Minneapolis and St. Paul, Minnesota (USA) marshes in late summer 2007, and we quantified land cover attributes within 500 m of the wetlands. Our surveys detected 24 species in the wetlands, including some not typically associated with wetlands. Bird species richness and diversity within wetlands were positively correlated with percent cover of trees and with cover of trees plus nontree vegetation near the wetlands, and they were negatively correlated with the cover of building footprints. Total bird detections during point counts were not correlated with vegetative aspects of land cover around the wetlands but were negatively correlated with cover of building footprints plus pavement within 150 m of the wetlands. Bird-land cover relationships were strongest when land cover within 200–500 m of the wetlands was considered and weaker when we considered only land cover within 25–50 m. Land use planning that both protects wetlands and emphasizes bird-friendly landscape design around wetlands may enhance avian diversity and abundance within the wetlands.
The only previous reported record of eastern small-footed bats (Myotis leibii) in Illinois was from a 2005 discovery of two individuals under a rock at the Fink Sandstone barrens of Shawnee National Forest (SNF). In Jun. 2011, the U.S. Fish and Wildlife Service requested information on the species to review potential listing under the Endangered Species Act. In response, managers at the SNF initiated a survey to determine if a resident population of eastern small-footed bats exists on the forest. We surveyed the SNF within Pope and Johnson Counties from 25 Jul.–16 Aug. 2011 by searching for day roosts under loose rocks on exposed rock outcrops. We discovered 29 individuals, including post lactating females and juveniles, along rock outcrops surrounding the 2005 site. While, the extent of M. leibii occurrence in Illinois is still poorly understood, our survey suggests that a resident breeding population occurs within the southern tip of the state.