439 research outputs found

    A meta-BACI approach forevaluating management intervention on chronic wasting disease in mule deer

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    Advances in acquiring and analyzing the spatial attributes of data have greatlyenhanced the potential utility of wildlife disease surveillance data for addressing problems ofecological or economic importance. We present an approach for using wildlife diseasesurveillance data to identify areas for (or of ) intervention, to spatially delineate pairedtreatment and control areas, and then to analyze these nonrandomly selected sites in a meta-analysis framework via beforeā€“afterā€“controlā€“impact (BACI) estimates of effect size. We applythese methods to evaluate the effectiveness of attempts to reduce chronic wasting disease(CWD) prevalence through intensive localized culling of mule deer (Odocoileus hemionus)innorth-central Colorado, USA. Areas where surveillance data revealed high prevalence or caseclusters were targeted by state wildlife management agency personnel for focal scale (onaverage ,17 km2) culling, primarily via agency sharpshooters. Each area of sustained cullingthat we could also identify as unique by cluster analysis was considered a potential treatmentarea. Treatment areas, along with spatially paired control areas that we constructed post hocin a case-control design (collectively called ā€˜ā€˜management evaluation sitesā€™ā€™), were thendelineated using home range estimators. Using meta-BACI analysis of CWD prevalence datafor all management evaluation sites, the mean effect size (change of prevalence on treatmentareas minus change in prevalence on their paired control areas) was 0.03 (SE Ā¼ 0.03); meaneffect size on treatment areas was not greater than on paired control areas. Excluding cullsamples from prevalence estimates or allowing for an equal or greater two-year lag in systemresponses to management did not change this outcome. We concluded that managementbeneļ¬ts were not evident, although whether this represented true ineffectiveness or was a resultof lack of data or insufļ¬cient duration of treatment could not be discerned. Based on ourobservations, we offer recommendations for designing a management experiment with 80%power to detect a 0.10 drop in prevalence over a 6ā€“12-year period

    Influence of Reproductive and Environmental Factors on Population Size .. of Wild Hyacinth [Camassia angusta (Engelm.Ā· and A. Gray) Blank. (Liliaceae)], an Illinois Endangered Species

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    Wild hyacinth (Camassia angusta) is a perennial species native to mesic prairies of the midwestern and south-central United States. In Illinois, the only extant population of this state-endangered species is in a small section of degraded black-soil prairie along a railroad track right-of-way south of Elwin, Macon County. The objectives of this study were to determine the population status, seed production, and effects of scarification and stratification on germination of C. angusta. The population was surveyed from 1990 to 2007. A survey of other plant species present was conducted in 1999. The site consisted of approximately 75% native and 25% exotic species. The number of flowering stems of Camassia angusta fluctuated significantly (28 to 169 plants) during the course of this study. Prescribed spring burns and a construction equipment disturbance may be partially responsible for these fluctuations. A large percentage of undeveloped fruit, resulting in low seed production ( \u3c3,000), as well as low seed germination (8%), may be responsible for this population\u27s inability to increase consistently in number of individuals

    Body-wave tomographic imaging of the Turkana Depression: Implications for rift development and plume-lithosphere interactions

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    The Turkana Depression, a topographically-subdued, broadly-rifted zone between the elevated East African and Ethiopian plateaus, disrupts the Nā€“S, fault-bounded rift basin morphology that characterizes most of the East African Rift. The unusual breadth of the Turkana Depression leaves unanswered questions about the initiation and evolution of rifting between the Main Ethiopian and Eastern rifts. Hypotheses explaining the unusually broad, low-lying area include superposed Mesozoic and Cenozoic rifting and a lack of mantle lithospheric thinning and dynamic support. To address these issues, we have carried out the first body-wave tomographic study of the Depressionā€™s upper mantle. Seismically-derived temperatures at 100ā€‰km depth exceed petrological estimates, suggesting the presence of mantle melt, although not as voluminous as the Main Ethiopian Rift, contributes to velocity anomalies. A NWā€“SE-trending high wavespeed band in southern Ethiopia at urn:x-wiley:15252027:media:ggge22580:ggge22580-math-0001200ā€‰km depth is interpreted as refractory Proterozoic lithosphere which has likely influenced the localization of both Mesozoic and Cenozoic rifting. At urn:x-wiley:15252027:media:ggge22580:ggge22580-math-0002100ā€‰km depth below the central Depression, a single localized low wavespeed zone is lacking. Only in the northernmost Eastern Rift and southern Lake Turkana is there evidence for focused low wavespeeds resembling the Main Ethiopian Rift, that bifurcate below the Depression and broaden approaching southern Ethiopia further north. These low wavespeeds may be attributed to melt-intruded mantle lithosphere or ponded asthenospheric material below lithospheric thin-spots induced by the region's multiple rifting phases. Low wavespeeds persist to the mantle transition zone suggesting the Depression may not lack mantle dynamic support in comparison to the two plateaus

    Spatio-temporal trends in normal-fault segmentation recorded by low-temperature thermochronology: Livingstone fault scarp, Malawi Rift, East African Rift System

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    The evolution of through-going normal-fault arrays from initial nucleation to growth and subsequent interaction and mechanical linkage is well documented in many extensional provinces. Over time, these processes lead to predictable spatial and temporal variations in the amount and rate of displacement accumulated along strike of individual fault segments, which should be manifested in the patterns of footwall exhumation. Here, we investigate the along-strike and vertical distribution of low-temperature apatite (Uā€“Th)/He (AHe) cooling ages along the bounding fault system, the Livingstone fault, of the Karonga Basin of the northern Malawi Rift. The fault evolution and linkage from rift initiation to the present day has been previously constrained through investigations of the hanging wall basin fill. The new cooling ages from the footwall of the Livingstone fault can be related to the adjacent depocentre evolution and across a relay zone between two palaeo-fault segments. Our data are complimented by published apatite fission-track (AFT) data and reveal significant variation in rock cooling history along-strike: the centre of the footwall yields younger cooling ages than the former tips of earlier fault segments that are now linked. This suggests that low-temperature thermochronology can detect fault interactions along strike. That these former segment boundaries are preserved within exhumed footwall rocks is a function of the relatively recent linkage of the system. Our study highlights that changes in AHe (and potentially AFT) ages associated with the along-strike displacement profile can occur over relatively short horizontal distances (of a few kilometres). This is fundamentally important in the assessment of the vertical cooling history of footwalls in extensional systems: temporal differences in the rate of tectonically driven exhumation at a given location along fault strike may be of greater importance in controlling changes in rates of vertical exhumation than commonly invoked climatic fluctuations

    The development of multiple phases of superposed rifting in the Turkana Depression, East Africa: evidence from receiver functions

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    The Turkana Depression in Eastern Africa separates the elevated plateaus of East Africa to the south and Ethiopia-Yemen to the north. It remains unclear whether the Depression lacks dynamic mantle support, or if the entire East Africa region is dynamically supported and the Depression compensated isostatically by thinned crust. Also poorly understood is how Miocene-Recent extension has developed across the Depression, connecting spatially separated magmatic rift zones in Ethiopia and Kenya. Receiver function analysis is used to constrain Moho depth and bulk-crustal V P /V S ratio below new seismograph networks in the Depression, and on the northern Tanzania craton. Crustal thickness is āˆ¼40 km below northern Uganda and 30ā€“35 km below southern Ethiopia, but 20ā€“30 km below most of the Depression, where mass-balance calculations reveal low elevations can be explained adequately by crustal thinning alone. Despite the fact that magmatism has occurred for 45 Ma across the Depression, more than 15 Ma before East African Rift (EAR) extension initiated, bulk crustal V P /V S across southern Ethiopia and the Turkana Depression (āˆ¼1.74) is similar to that observed in areas unaffected by Cenozoic rifting and magmatism. Evidence for voluminous lower crustal intrusions and/or melt, widespread below the Ethiopian rift and Ethiopian plateau to the north, is therefore lacking. These observations, when reviewed in light of high stretching factors (Ī² ā‰¤ 2.11), suggest Cenozoic extension has been dominated until recently by faulting and plate stretching, rather than magma intrusion, which is likely an incipient process, operating directly below seismically-active Lake Turkana. Early-stage EAR basins to the west of Lake Turkana, with associated stretching factors of Ī² ā‰ˆ 2, formed in crust only moderately thinned during earlier rifting episodes. Conversely, āˆ¼23 km-thick crust beneath the Kino Sogo Fault Belt (KSFB) has small offset faults and thin sedimentary strata, suggesting almost all of the observed stretching occurred in Mesozoic times. Despite the KSFB marking the shortest path between focused extensional zones to the north and south, seismicity and GPS data show that modern extension is localized below Lake Turkana to the west. Failed Mesozoic rift zones, now characterized by thinned crust and relatively refractory mantle lithosphere, are being circumnavigated, not exploited by EAR rifting

    Surveys of Stylisma Pickeringii var. Pattersonii (Convolvulaceae), its Associated Plant Species, and its Insect Visitors

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    Stylisma pickeringii var. pattersonii (Convolvulaceae) is endangered in Illinois and Iowa, and occurs in scattered populations in other states. During 1999 and 2000, two insect species previously unreported from Illinois were observed visiting its flowers. This study was undertaken to survey additional insect visitors, as well as to characterize the plant community where S. pickeringii occurs. The objectives were to survey: 1) floral traits (anthesis and flower density) of S. pickeringii, 2) associated plant species, and 3) insect visitor characteristics. Floral traits were determined and associated plant species surveyed in Mason County (degraded hay field on private property) and Henderson County (dry sand prairie at the Big River State Forest), Illinois. Insects visiting flowers were collected at 10:00 a.m., 12:30 p.m., and 3:00 p.m. during June, July, and August in 2001 and 2002. Individual flowers lasted one day and remained open for 6ā€“8 hours. Peak flowering occurred from early to the middle of July when S. pickeringii was the dominant species in flower. Henderson County contained a greater diversity of native plant species with less bare ground and fewer non-native species than the Mason County site. Fortyseven insect species were observed visiting S. pickeringii flowers. Most frequent visitors were Apis mellifera (Hymenoptera: Apidae), Bombylius fraudulentus (Diptera: Bombyliidae), and Heterostylum croceum (Diptera: Bombliidae). The diversity of visiting insects was higher earlier than later in the day, in July and August than June, and in Henderson than Mason County

    Density Dependence, Whitebark Pine Decline and Vital Rates of Grizzly Bears in The Greater Yellowstone Ecosystem

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    Recent evidence suggests annual population growth of the grizzly bear (Ursus arctos) population in the Greater Yellowstone Ecosystem has slowed from 4.1ā€“7.6 percent during 1983ā€“2001 to 0.3ā€“2.2 percent during 2002ā€“2011. Substantial changes in availability of an important fall food has occurred over the past decade. Whitebark pine (Pinus albicaulis), a highly variable but important fall food source for grizzly bears, has experienced substantial mortality due to a mountain pine beetle (Dendroctonus ponderosae) outbreak that started in the early 2000s. Concurrent with changes in food resources, the grizzly bear population has reached high densities in some areas and has continued to expand, now occupying >50,000 km2. We tested research hypotheses to examine if changes in vital rates detected during the past decade were more associated with grizzly bear density versus a whitebark pine decline. We focused our assessment on known-fate data to estimate survival of cubs-of-the-year, yearlings, and independent bears (? 2 yrs) and reproductive transition of females from having no offspring to having cubs.Ā  We observed a change in survival of independent bears between the periods of 1983ā€“2001 and 2002ā€“2012, which was mostly a function of increased male survival; female survival did not change. Cub survival and reproductive transition declined during the last decade and were associated with an index of grizzly bear density, which indicated increasing density over time. We found no support that the decline in these vital rates was associated with the index of whitebark decline

    Elk Contact Patterns and Potential Disease Transmission

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    Understanding the drivers of contact rates among individuals is critical to understanding disease dynamics and implementing targeted control measures. We studied the interaction patterns of 149 female elk (Cervus elaphus) distributed across five different regions of western Wyoming over three years, defining a contact as an approach within one body length (~2m). Using hierarchical models that account for correlations within individuals, pairs and groups, we found that pairwise contact rates within a group declined by a factor of three as group sizes increased 30-fold. Meanwhile, per capita contact rates increased with group size due to the increasing number of potential pairs. We found similar patterns for the duration of contacts. Supplemental feeding of elk had a limited impact on pairwise interaction rates and durations, but increased per capita rates more than two times higher. Variation in contact patterns were driven more by environmental factors such as group size than either individual or pairwise differences. Female elk in this region fall between the expectation of contact rates that linearly increase with group size (as assumed by pseudo-mass action models of disease transmission) or are constant with changes in group size (as assumed by frequency dependent transmission models). Our statistical approach decomposes the variation in contact rate into individual, dyadic, and environmental effects, which provides insight into those factors that are important for effective disease control programs

    Influence of Whitebark Pine Decline on Fall Habitat Use and Movements of Grizzly Bears in the Greater Yellowstone Ecosystem

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    Seeds of whitebark pine (WBP; Pinus albicaulis) are a major food item for grizzly bears (Ursus arctos) in the greater Yellowstone ecosystem. Higher rates of bear mortality and bear-human conflicts are linked with low WBP productivity. Recently, infestations of mountain pine beetle (Dendroctonus ponderosae) have killed many mature, cone-bearing WBP trees. We investigated whether this decline caused bears to reduce their use of WBP and increase use of areas near humans. We used 52,332 GPS locations of 72 individuals (89 bear-years) monitored during fall (15 Augā€“30 Sep) to examine temporal changes in habitat use and movements during 2000ā€“2011. We calculated a Manley-Chesson (MC) index for selectivity of mapped WBP habitats for each individual within its 100% local convex hull home range, and determined dates of WBP use. One third of sampled grizzly bears had fall ranges with little or no mapped WBP habitat. Most other bears (72%) had a MC index > 0.5, indicating selection for WBP habitats. Over the study period, mean MC index decreased and median date of WBP use shifted about 1 week later. We detected no trends in movement indices over time. Outside of national parks, 78 percent of bears selected for secure habitat (areas ? 500 m from roads), but mean MC index decreased over the study period during years of good WBP productivity. The foraging plasticity of grizzly bears likely allowed them to adjust to declining WBP. However, the reduction in mortality risk associated with use of WBP habitat may be diminishing for bears in multiple-use areas
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