2,838 research outputs found

    Short and long distance translocations: Movement and survival in eastern box turtles (_Terrapene carolina carolina_)

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    *Background/Question/Methods*

Human development represents a serious threat to wildlife populations through continued habitat loss and incidental mortality from construction activities. Resource managers responsible for protecting species with legal status or high public profile are faced with difficult decisions on how to best manage populations located in construction zones. One approach to mitigate mortalities is to relocate individuals. The effectiveness of translocation for reptiles and amphibians has been questioned, with studies often reporting higher mortality and increased movements of translocated individuals. Translocations of reptiles and amphibians have primarily involved moving animals long distances, well beyond an individual’s home range. For reptiles this means finding new nesting, foraging, and overwintering sites, which may be problematic. Moving individuals only short distances, within their home range, may reduce those problems. As part of the mitigation plan for a highway construction project in central Maryland, groups of eastern box turtles (Terrapene carolina carolina) were translocated both short distances (<0.5km), and long distances (~5km). To investigate differences in survival and movement patterns among long distance translocation, short distance translocation, and non-translocation groups, I tracked 94 turtles (31 long distance translocation, 29 short distance translocation, and 34 non-translocation) using radio telemetry. 

*Results/Conclusions*

Eleven animals died during the first activity season after translocation (April through November 2008). The mortalities included two long distance translocation, six short distance translocation, and three non-translocation animals. The causes of mortality included road kill, construction activity, and unknown (1, 4, and 6 mortalities respectively). All construction related mortalities were a result inadequate exclusion fencing to keep turtles from trespassing back onto the construction site. All mortalities due to construction were either non-translocation or short distance translocation animals. Eleven other individuals were located at least once within the construction zone, suggesting that without our intervention mortality rates would have been much higher. Preliminary results for movement show that turtles in the non-translocation group had the lowest average movements while long distance translocation animals had the greatest average movements. Long distance translocation turtles also chose overwintering sites farther away from their initial overwintering sites than either short distance translocation or non-translocation turtles (average distance from original site of 261.8m, 155.6m, and 124.3m respectively). This suggests that movement patterns of short distance translocation turtles are more like native turtles.
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    Hydrous Manganese Oxide Doped Gel Probe Sampler for Measuring In Situ Reductive Dissolution Rates. 2. Field Deployment

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    In situ rates of reductive dissolution in submerged shoreline sediments at Lake Tegel (Berlin, Germany) were measured with a novel hydrous manganese (Mn) oxide-doped gel probe sampler in concert with equilibrium gel probe and sequential extraction measurements. Rates were low in the top 8 cm, then showed a peak from 8 to 14 cm, with a maximum at 12 cm depth. This rate corresponded with a peak in dissolved porewater iron (Fe) at 11 cm depth. Below 14 cm, the reductive dissolution rate reached an intermediate steady value. Lower rates at depth corresponded with increases in operationally defined fractions of carbonate-bound and organic- and sulfide-bound Mn and Fe as detected by sequential extraction. Observed rates of reductive dissolution, which reflect a capacity for Mn reduction rather than actual rates under ambient conditions, appear to correlate with porewater chemistry and sequential extraction fractions as expected in early sediment diagenesis, and are consistent with previous measurements of in situ reductive dissolution rates. Significant downward advection in this bank filtration setting depletes the Mn and Fe oxides in the sediments and enhances the transport of dissolved Fe and Mn into the infiltrating water

    COMMUNITY SUPPORTED AGRICULTURE: FILLING A NICHE MARKET

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    In less than a decade, the number of Community Supported Agriculture (CSA) projects has grown to more than 400. Our research suggests that CSA shareholders' social objectives dominate their decision to join. Standard economic objectives and "club-related" objectives contribute to the decision, but are clearly secondary. Our research also suggests the CSA movement will continue to grow. Its emphasis on social objectives, its inability to supply food year around, and the ongoing development of size-neutral organic technologies, however, will probably keep it from becoming a major market channel in the next century.Agribusiness,

    The Final SDSS High-Redshift Quasar Sample of 52 Quasars at z>5.7

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    We present the discovery of nine quasars at z6z\sim6 identified in the Sloan Digital Sky Survey (SDSS) imaging data. This completes our survey of z6z\sim6 quasars in the SDSS footprint. Our final sample consists of 52 quasars at 5.7<z6.45.7<z\le6.4, including 29 quasars with zAB20z_{\rm AB}\le20 mag selected from 11,240 deg2^2 of the SDSS single-epoch imaging survey (the main survey), 10 quasars with 20zAB20.520\le z_{\rm AB}\le20.5 selected from 4223 deg2^2 of the SDSS overlap regions (regions with two or more imaging scans), and 13 quasars down to zAB22z_{\rm AB}\approx22 mag from the 277 deg2^2 in Stripe 82. They span a wide luminosity range of 29.0M145024.5-29.0\le M_{1450}\le-24.5. This well-defined sample is used to derive the quasar luminosity function (QLF) at z6z\sim6. After combining our SDSS sample with two faint (M145023M_{1450}\ge-23 mag) quasars from the literature, we obtain the parameters for a double power-law fit to the QLF. The bright-end slope β\beta of the QLF is well constrained to be β=2.8±0.2\beta=-2.8\pm0.2. Due to the small number of low-luminosity quasars, the faint-end slope α\alpha and the characteristic magnitude M1450M_{1450}^{\ast} are less well constrained, with α=1.900.44+0.58\alpha=-1.90_{-0.44}^{+0.58} and M=25.23.8+1.2M^{\ast}=-25.2_{-3.8}^{+1.2} mag. The spatial density of luminous quasars, parametrized as ρ(M1450<26,z)=ρ(z=6)10k(z6)\rho(M_{1450}<-26,z)=\rho(z=6)\,10^{k(z-6)}, drops rapidly from z5z\sim5 to 6, with k=0.72±0.11k=-0.72\pm0.11. Based on our fitted QLF and assuming an IGM clumping factor of C=3C=3, we find that the observed quasar population cannot provide enough photons to ionize the z6z\sim6 IGM at 90\sim90\% confidence. Quasars may still provide a significant fraction of the required photons, although much larger samples of faint quasars are needed for more stringent constraints on the quasar contribution to reionization.Comment: 20 pages, 12 figures, Accepted for publication in The Astrophysical Journa
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