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Most surveys for bats are conducted using mist nets in riparian areas along stream corridors. Various methods exist for deploying mist nets, but success of using different configurations has not been assessed. We tested efficiency of three configurations of mist nets during summers of 2000 and 2001 at the Milan Army Ammunition Plant (Carroll and Gibson counties) in western Tennessee. Configurations of mist nets included: I (one net placed transverse to stream), T (one net placed transverse to stream, and one net positioned perpendicular to first net in midstream), and Z (two nets positioned parallel to stream, and a center net positioned diagonally between the two nets). The study consisted of 347 net nights and 220 captures of bats (85 I, 62 T, 73 Z). Four species were captured including: 133 Lasiurus borealis, 63 Perimyotis subflavus, 15 Nycticeius humeralis, and nine Myotis austroriparius. Sex-ratios for adults were female biased, while juvenile sex-ratios were near equal. Netting results suggest that traditional I-configurations were statistically equal to T- and Z-configurations for all analyses of total captures and for the two dominant species captured: L. borealis and P. subflavus. Because the I-configuration requires less equipment and time for set-up, capturing bats in linear corridors could be optimized by using more I-nets rather than multiple net configurations.
In western Mexico, gray mouse opossums Tlacuatzin canescens typically are not only in tropical deciduous and semideciduous woodlands but also in croplands and orchards. We conducted mark-recapture studies in January 2003–2007 and 2010 in coastal, northern, and central Colima, Mexico. Each year, five grids, established in areas of thick vegetation within a mosaic of habitats, had 100 stations (10 × 10), each with two Sherman traps, one on the ground and another elevated 1–2 m. On 24 of 30 grids, 82 individuals were captured 126 times (85.7 % in elevated traps). Sex ratio did not deviate from 1:1; there was no sexual dimorphism in mass (average for males, 28.21 g; average for females, 25.64 g); 46.3 % of animals were adults, 27.3 % of adult females were reproductively active, and 77.5 % of males had scrotal testes. Distance from centroid of trap locations averaged 15.24 m, with mean minimum distance moved between captures being 33.19 m. Densities usually were low (0.67–8.03/ha), with the species widespread in habitats studied. We assessed 14 environmental characteristics for each station using ANOVA, logistic regression, and nonparametric multiplicative regression (NPMR) to characterize habitat selection. T. canescens was more likely found where percent grass was about 30 % and litter over 50 %, with height of canopy less than 10 m and about 40 % closed. NPMR, being able to recognize hump-shaped response curves where intermediate variable values are preferred, identified two variables (percent grass and percent canopy closed) not detected by other techniques as important in characterizing habitat selection of T. canescens.
Flight speeds of Pallas's long-tongued bat (Glossophaga soricina), the Mexican funnel-eared bat (Natalus stramineus), and the gray short-tailed bat (Carollia subrufa) were measured in Colima, Mexico, during January 2006. Bats from an abandoned mine tunnel were transported to a nearby simulated flyway, where speeds were determined over a known distance. For G. soricina, average speeds for 26 males and 14 females were 4.85 and 4.80 m/s, respectively (P > 0.05), which are similar to those reported by other investigators. Averages for N. stramineus were 2.84 m/s for 40 males and 2.39 m/s for 23 females, values that were statistically different (P < 0.05) despite the fact that body masses for the sexes were similar. For C. subrufa, three males and three females averaged 3.67 and 3.52 m/s, respectively. Speeds were unrelated to body mass for any of the species. Speeds for N. stramineus and C. subrufa are the first reported, whereas those for G. soricina are the first recorded under near-field conditions.
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