Learning of foraging skills by fish

This chapter outlines the relationships between a number of key factors that influence learning and memory, and illustrates them by reference to studies on the foraging behaviour of fish. Learning can lead to significant improvements in foraging performance in only a few exposures, and at least some fish species are capable of adjusting their foraging strategy as patterns of patch profitability change. There is also evidence that the memory window for prey varies between fish species, and that this may be a function of environmental predictability. Convergence between behavioural ecology and comparative psychology offers promise in terms of developing more mechanistically realistic foraging models and explaining apparently 'suboptimal' patterns of behaviour. Foraging decisions involve the interplay between several distinct systems of learning and memory, including those that relate to habitat, food patches, prey types, conspecifics and predators. Fish biologists, therefore, face an interesting challenge in developing integrated accounts of fish foraging that explain how cognitive sophistication can help individual animals to deal with the complexity of the ecological context.

Predator-specific changes in the morphology and swimming performance of larval Rana lessonae

1. We investigated the morphological responses of larval Rana lessonae to the presence of two predators with substantially different prey-detection and capture techniques; larval dragonflies (Aeshna cyanea) and the Pumpkinseed Sunfish (Lepomis gibossus). 2. We also examined the functional implications of any predator-induced morphological variation on their swimming ability by assessing performance during the initial stages of a startle response. 3. We found the morphological responses of larval R. lessonae were dependent on the specific predator present. Tadpoles raised in the presence of dragonfly larvae preying upon conspecific tadpoles developed total tail heights 5.4% deeper and tail muscles 4.7% shallower than tadpoles raised in a non-predator environment, while tadpoles raised with sunfish possessed tails 2% shallower and tail muscles 2.5% higher than non-predator-exposed tadpoles. 4. Predator-induced morphological variation also significantly influenced swimming performance. Tadpoles raised with sunfish possessed swimming speeds 9.5 and 14.6% higher than non- and dragonfly predator groups, respectively. 5. Thus, the expression of these alternative predator-morphs leads to a functional trade-off in performance between the different environments.

The oil shock of 2005

During the course of 2005, the price of crude oil reached unprecedented high levels, at least in nominal terms. Australian motorists have become used to paying more than a dollar a litre for petrol. Given the past volatility in oil prices, often described in terms of a series of oil ‘shocks’ (the large price increases in 1973, 1979 and 1999), several questions arise. First, will current high prices persist, or will prices decline substantially as occurred after previous oil shocks? Second, is the current shortage of oil a temporary phenomenon, caused by inadequate investment in oil exploration, drilling and refining capacity, or is it a signal that the supply of oil available to the world has peaked? Third, will high oil prices lead to broader economic disruption, as is commonly supposed to have happened after previous shocks? Fourth, how painful will an adjustment to lower use of oil be? Finally, how does all this relate to our efforts to deal with the problem of climate change? This article is an effort to answer some of these questions in the light of the knowledge available to us.

Evidence-based medicine is affordable: The cost-effectiveness of current compared with optimal treatment in rheumatoid and osteoarthritis

Objective. To determine the cost-effectiveness of averting the burden of disease. We used secondary population data and metaanalyses of various government-funded services and interventions to investigate the costs and benefits of various levels of treatment for rheumatoid arthritis (RA) and osteoarthritis (OA) in adults using a burden of disease framework. Method. Population burden was calculated for both diseases in the absence of any treatment as years lived with disability (YLD), ignoring the years of life lost. We then estimated the proportion of burden averted with current interventions, the proportion that could be averted with optimally implemented cut-rent evidence-based guidelines, and the direct treatment cost-effectiveness ratio in dollars per YLD averted for both treatment levels. Results. The majority of people with arthritis sought medical treatment. Current treatment for RA averted 26% of the burden, with a cost-effectiveness ratio of $19,000 per YLD averted. Optimal, evidence-based treatment would avert 48% of the burden. with a cost-effectiveness ratio of $12,000 per YLD averted. Current treatment of OA in Australia averted 27% of the burden, with a cost-effectiveness ratio of $25,000 per YLD averted. Optimal, evidence-based treatment would avert 39% of the burden, with an unchanged cost-effectiveness ratio of $25,000 per YLD averted. Conclusion. While the precise dollar costs in each country will differ, the relativities at this level of coverage should remain the same. There is no evidence that closing the gap between evidence and practice would result in a drop in efficiency.

The consumption of alcohol by Australian adolescents: A comparison of revenue and expenditure

Aims: To estimate (i) Australian government taxation revenue collected from the consumption of alcohol by adolescents and (ii) the amount spent by the government on interventions aimed at educating adolescents about the potential dangers of alcohol use. Design: Secondary data analysis. Setting: Australia. Findings: Australian adolescents (aged between 12 and 17 years, inclusive) spent approximately $217 million on alcoholic beverages in 2002, netting the Australian government approximately $112 million in tax revenue. This resulted in an average of $195 earned in tax per adolescent drinker. It is estimated that the Government spent approximately $17 million on adolescent drinking interventions in 2002, equating to an expenditure of about $10.51 per adolescent on the delivery of alcohol interventions. For every dollar spent on alcohol interventions aimed at adolescents, it is estimated that the government receives around $7 in alcohol tax revenue. Conclusions: A substantial disparity exists between the amount of tax revenue received by the Australian Government from adolescent drinkers and the overall amount spent in attempting to prevent and relieve some of the problems associated with adolescent problem drinking. (c) 2006 Elsevier Ltd. All rights reserved.

The wealth effect of housing on aggregate consumption

This study Measures the effect of changes in net housing and financial wealth oil household consumption using Australian data over the period Q2:1988-Q1:2003. It is found a permanent one dollar rise in housing wealth leads to a six cent increase in consumption, three times the effect of financial wealth. The result speaks strongly against the notion of assets fungibility.. and Suggests that a sharp movement in house prices is potentially more disruptive than a corresponding movement ill financial asset prices.