How energy costs affect foraging decisions is poorly understood for marine animals. To provide data relevant to this topic,
we examined the relationship between activity levels and foraging behavior by attaching activity recorders to 29 chick-rearing
wing-propelled diving birds (thick-billed murres, Uria lomvia) in 1999–2000. We connected the activity during the final dive bout with the prey item we observed being fed to the chicks.
After accounting for changes in activity level with depth, activity was highest during the final dive of a dive bout, reflecting
maneuvring during prey capture. Pelagic prey items, especially invertebrates (amphipods), were associated with higher depth-corrected
activity, leading to shorter dives for a given depth (presumably due to higher oxygen consumption rates) and, thus, shorter
search times (lower bottom time for a given depth). Pelagic prey items were likely captured during active pursuit, with the
birds actively seeking and pursuing schooling mid-water prey. In contrast, benthic prey involved low activity and extended
search times, suggesting that the birds slowly glided along the bottom in search for prey hidden in the sediments or rocks.
We concluded that activity levels are important in determining the foraging tactics of marine predators.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
This paper argues that the delay required for resolution of uncertainty in the technical information for policy making depends on how the relevant policy issues are posed. The relationship between CO2 and global mean temperature is used to illustrate the argument in terms of the testing of specific hypotheses. 相似文献
Objective: Driver sleepiness contributes substantially to road crash incidents. Simulator and on-road studies clearly reveal an impairing effect from sleepiness on driving ability. However, the degree to which drivers appreciate the dangerousness of driving while sleepy is somewhat unclear. This study sought to determine drivers' on-road experiences of sleepiness, their prior sleep habits, and personal awareness of the signs of sleepiness.
Methods: Participants were a random selection of 92 drivers traveling on a major highway in the state of Queensland, Australia, who were stopped by police as part of routine drink driving operations. Participants completed a brief questionnaire that included demographic information, sleepy driving experiences (signs of sleepiness and on-road experiences of sleepiness), and prior sleep habits. A modified version of the Karolinska Sleepiness Scale (KSS) was used to assess subjective sleepiness in the 15 min prior to being stopped by police.
Results: Participants' ratings of subjective sleepiness were quite low, with 90% reporting being alert to extremely alert on the KSS. Participants were reasonably aware of the signs of sleepiness, with many signs of sleepiness associated with on-road experiences of sleepiness. Additionally, the number of hours spent driving was positively correlated with the drivers' level of sleep debt.
Conclusions: The results suggest that participants had moderate experiences of driving while sleepy and many were aware of the signs of sleepiness. The relationship between driving long distances and increased sleep debt is a concern for road safety. Increased education regarding the dangers of sleepy driving seems warranted. 相似文献
Capillary electrophoresis coupled to mass spectrometry(CE–MS) was used for the analysis of naphthenic acid fraction compounds(NAFCs) of oil sands process-affected water(OSPW). A standard mixture of amine-derivatized naphthenic acids is injected directly onto the CE column and analyzed by CE–MS in less than 15 min. Time of flight MS analysis(TOFMS), optimized for high molecular weight ions, showed NAFCs between 250 and 800 m/z. With a quadrupole mass analyzer, only low-molecular weight NAFCs(between 100 and 450 m/z) are visible under our experimental conditions. Derivatization of NAFCs consisted of two-step amidation reactions mediated by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide(EDC), or mediated by a mixture of EDC and N-hydroxysuccinimide, in dimethyl sulfoxide, dichloromethane or ethyl acetate. The optimum background electrolyte composition was determined to be 30%(V/V) methanol in water and 2%(V/V) formic acid. NAFCs extracted from OSPW in the Athabasca oil sands region were used to demonstrate the feasibility of CE–MS for the analysis of NAFCs in environmental samples, showing that the labeled naphthenic acids are in the mass range of 350 to 1500 m/z. 相似文献