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Experimental Field Study (experimental + field_study)
Selected AbstractsExperimental field study of the relative costs and benefits to wild tamarins (saguinus imperator and S. fuscicollis) of exploiting contestable food patches as single- and mixed-species troopsAMERICAN JOURNAL OF PRIMATOLOGY, Issue 4 2003Júlio César Bicca-Marques Abstract Several species of tamarins form stable mixed-species troops in which groups of each species feed, forage, rest, and travel together during much of the year. Although the precise set of factors that facilitate this ecological relationship remains unclear, predator detection and foraging benefits are presumed to play a critical role in maintaining troop stability. In this work we present data from an experimental field study designed to examine how factors such as social dominance and within-patch foraging decisions affect the costs and benefits to tamarins of visiting feeding sites as single- and mixed-species troops. Our data indicate that when they exploited contestable food patches (sets of eight feeding platforms, two of which contained a 100-g banana), each tamarin species experienced foraging costs when they arrived as part of a mixed-species troop. These costs were found to be less severe for emperor tamarins because they were socially dominant to saddle-back tamarins and could displace them at feeding sites. We conclude that the foraging benefits to tamarins residing in mixed-species troops are asymmetrical, and that at feeding sites in which the amount of food in a patch is insufficient to satiate all troop members, even minor differences in the timing of return to food patches and changes in troop cohesion have a measurable effect on the costs and benefits to participating tamarin species. Am. J. Primatol. 60:139,153, 2003. © 2003 Wiley-Liss, Inc. [source] Is the Political Skill Inventory Fit for Personnel Selection?INTERNATIONAL JOURNAL OF SELECTION AND ASSESSMENT, Issue 2 2010An Experimental Field Study The political skill inventory (PSI) assesses social effectiveness in organizations by self-reports and has demonstrated strong evidence of validity. It was the purpose of this experimental field study to investigate construct and criterion-related validity of the PSI when used under conditions of personnel selection. In the experimental group (n=102), the instructions asked job incumbents to work on the PSI, a social desirability scale, and a Big-Five personality inventory as if they took part in a personnel selection procedure for a personally very attractive position. Additionally, they were asked to report yearly income. In the control group (n=110), job incumbents were asked to answer the items honestly. As expected, in both conditions, the PSI did not correlate with social desirability, but it correlated positively with extraversion, conscientiousness, and income, and negatively with neuroticism, thus demonstrating construct and incremental criterion-related validity under both conditions. Implications and limitations are discussed. [source] Proximate mechanisms of variation in the carotenoid-based plumage coloration of nestling great tits (Parus major L.)JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2003B. Tschirren Abstract Many vertebrates use carotenoid-based signals in social or sexual interactions. Honest signalling via carotenoids implies some limitation of carotenoid-based colour expression among phenotypes in the wild, and at least five limiting proximate mechanisms have been hypothesized. Limitation may arise by carotenoid-availability, genetic constraints, body condition, parasites, or detrimental effects of carotenoids. An understanding of the relative importance of the five mechanisms is relevant in the context of natural and sexual selection acting on signal evolution. In an experimental field study with carotenoid supplementation, simultaneous cross-fostering, manipulation of brood size and ectoparasite load, we investigated the relative importance of these mechanisms for the variation in carotenoid-based coloration of nestling great tits (Parus major). Carotenoid-based plumage coloration was significantly related to genetic origin of nestlings, and was enhanced both in carotenoid-supplemented nestlings, and nestlings raised in reduced broods. We found a tendency for ectoparasite-induced limitation of colour expression and no evidence for detrimental effects of carotenoids on growth pattern, mortality and recruitment of nestlings to the local breeding population. Thus, three of the five proposed mechanisms can generate individual variation in the expression of carotenoid-based plumage coloration in the wild and thus could maintain honesty in a trait potentially used for signalling of individual quality. [source] Experimental field study of the relative costs and benefits to wild tamarins (saguinus imperator and S. fuscicollis) of exploiting contestable food patches as single- and mixed-species troopsAMERICAN JOURNAL OF PRIMATOLOGY, Issue 4 2003Júlio César Bicca-Marques Abstract Several species of tamarins form stable mixed-species troops in which groups of each species feed, forage, rest, and travel together during much of the year. Although the precise set of factors that facilitate this ecological relationship remains unclear, predator detection and foraging benefits are presumed to play a critical role in maintaining troop stability. In this work we present data from an experimental field study designed to examine how factors such as social dominance and within-patch foraging decisions affect the costs and benefits to tamarins of visiting feeding sites as single- and mixed-species troops. Our data indicate that when they exploited contestable food patches (sets of eight feeding platforms, two of which contained a 100-g banana), each tamarin species experienced foraging costs when they arrived as part of a mixed-species troop. These costs were found to be less severe for emperor tamarins because they were socially dominant to saddle-back tamarins and could displace them at feeding sites. We conclude that the foraging benefits to tamarins residing in mixed-species troops are asymmetrical, and that at feeding sites in which the amount of food in a patch is insufficient to satiate all troop members, even minor differences in the timing of return to food patches and changes in troop cohesion have a measurable effect on the costs and benefits to participating tamarin species. Am. J. Primatol. 60:139,153, 2003. © 2003 Wiley-Liss, Inc. [source] Impact of feral water buffalo and fire on growth and survival of mature savanna trees: An experimental field study in Kakadu National Park, northern AustraliaAUSTRAL ECOLOGY, Issue 6 2005PATRICIA A. WERNER Abstract The impact of feral Asian water buffalo (Bubalus bubalis) and season of fire on growth and survival of mature trees was monitored over 8 years in the eucalypt savannas of Kakadu National Park. Permanently marked plots were paired on either side of a 25-km-long buffalo-proof fence at three locations on an elevational gradient, from ridge-top to the edge of a floodplain; buffalo were removed from one side of the fence. All 750 trees ,,1.4 m height were permanently marked; survival and diameter of each tree was measured annually; 26 species were grouped into four eco-taxonomic groups. The buffalo experiment was maintained for 7 years; trees were monitored an additional year. Fires were excluded from all sites the first 3 years, allowed to occur opportunistically for 4 years and excluded for the final year. Fires were of two main types: low-intensity early dry season and high-intensity late dry season. Growth rates of trees were size-specific and positively related to diameters as exponential functions; trees grew slowest on the two ends of the gradient. Eucalypt mortality rates were 1.5 and 3 times lower than those of pantropics and of arborescent monocots, respectively, but the relative advantage was lost with fires or buffalo grazing. Without buffalo grazing, ground level biomass was 5,8 t ha,1 compared with 2,3 t ha,1, within 3 years. In buffalo-absent plots, trees grew significantly slower on the dry ridge and slope, and had higher mortality across the entire gradient, compared with trees in buffalo-present plots. At the floodplain margin, mortality of small palms was higher in buffalo-present sites, most likely due to associated heavy infestations of weeds. Low-intensity fires produced tree growth and mortality values similar to no-fire, in general, but, like buffalo, provided a ,fertilization' effect for Eucalyptus miniata and Eucalyptus tetrodonta, increasing growth in all size classes. High-intensity fires reduced growth and increased mortality of all functional groups, especially the smallest and largest (>35 cm d.b.h.) trees. When buffalo and fires were excluded in the final year, there were no differences in growth or mortality between paired sites across the environmental gradient. After 8 years, the total numbers of trees in buffalo-absent plots were only 80% of the number in buffalo-present plots, due to relatively greater recruitment of new trees in buffalo-present plots; fire-sensitive pantropics were particularly disadvantaged. Since the removal of buffalo is disadvantageous, at least over the first years, to savanna tree growth and survival due to a rebound effect of the ground-level vegetation and subsequent changes in fire-vegetation interactions, process-orientated management aimed at reducing fuel loads and competitive pressure may be required in order to return the system to a previous state. The ,footprint' of 30 years of heavy grazing by buffalo has implications for the interpretation of previous studies on fire-vegetation dynamics and for current research on vegetation change in these savannas. [source] | ||||||||||