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Effects of Endogenous Risks in Contract Design : A Theoretical and Empirical Analysis of the Optimal Contract Design in the Swedish Construction Industry / Effekter av endogena risker i kontraktsdesign : En teoretisk och empirisk analys av den optimala kontraktsdesignen inom den svenska byggindustrinDe Barros Cruz, Julio Cesar January 2021 (has links)
The architecture, engineering and construction industry faces challenges when dealing withprocurement contract design and risk-handling. The optimal contracting practices have beenworldwide studied in areas of contract theory which studies how the optimal incentivemechanism (“contracts”) can be designed to encourage the parties to behave more efficiently.The parties usually consist of a principal and an agent, where the principal hires an agent todeliver goods or services. However, the complexity of contract theory calls for a morepracticable approach in an attempt to understand the procurement problem in the industry andincrease knowledge-sharing between projects. The purpose of this study is to propose a model based on contract theory that can be used inpractice to investigate the effects of project endogenous risks in three different types ofprocurement contracts: fixed-price, time and material, and incentive. Thus, this study usesquantitative methods with the aim to explain the current procurement problem in the Swedisharchitecture, engineering, and construction industry, compare theory and practice, andcontribute to knowledge about the linkage between endogenous risks, optimal risk sharing andcontract design. The conclusions from this study are that the current contracting practices in the industry arenot aligned with the optimal contract design described by the theory. The theory in this researchshowed that, given endogenous project risks, the optimal incentives vary in the agent’saversion to risk resulting in a non-monotone relationship between optimal contract power andproject risk. Further, a contract becomes optimal and efficient when cost savings and qualityincentives are aligned. However, the analysis of real-world projects presented no clearrelationship between contract power and project risk, i.e. some projects with fixed-pricecontracts or time and material contracts presented the same risk level. Hence, this researchproposes a method for computing the optimal incentive contract which can be used in manycases where the other two types of contract are currently being used. Based on the theory, theoptimal incentive contract may add valuable benefits for both parties involved since it aims toefficiently share the project risk between them while providing the agent the right incentivesto work more efficiently to reduce costs and deliver high-quality services or goods. / Byggbranschen står inför utmaningar när det gäller kontraktsdesign och riskhantering. Deoptimala upphandlingsmetoderna har studerats över hela världen inom områden avkontraktsteori som i sin tur studerar hur den optimala incitamentsmekanismen ("kontrakt") kanutformas för att uppmuntra parterna att agera mer effektivt. Parterna består vanligtvis av enprincipal och en agent, där principalen anställer en agent för att leverera varor eller tjänster.Men komplexiteten i kontraktsteori kräver ett mer praktiskt tillvägagångssätt i ett försök attbättre förstå upphandlingsproblemet i byggbranschen samt att öka kunskapsutbytet mellanprojekt. Syftet med denna studie är att föreslå en modell baserad på kontraktsteori som kan användas ipraktiken för att undersöka effekter av endogena risker i tre olika typer avupphandlingskontrakt: fastpris, rörligt pris (time and material) och incitament. Denna studieanvänder därmed kvantitativa metoder i syfte att förklara det aktuella upphandlingsproblemeti den svenska byggbranschen, jämföra teori och praktik, och bidra till utökad kunskap omsambandet mellan endogena risker, optimal riskdelning och kontraktsdesign. Slutsatsen från denna studie är att den nuvarande upphandlingspraxisen i branschen inte är ilinje med den optimala kontraktsdesignen som beskrivs av teorin. Teorin i denna studie visaratt, förutsatt endogena projektrisker, så varierar de optimala incitamenten med agentensriskaversion vilket resulterar i ett icke-monoton förhållande mellan optimal kontraktsdesignoch projektrisk. Dessutom blir ett kontrakt optimalt och effektivt när kostnadsbesparingar ochkvalitetsincitament är i linje med varandra. Men analysen av verkliga projekt visar inget tydligtsamband mellan kontraktsdesign och projektrisk, det vill säga en del projekt med fastpris ellerrörligt pris visade sig ha samma risknivå. Därför föreslår denna studie en metod för beräkningav det optimala incitamentet som kan användas i många fall där de andra två typerna avkontrakt för närvarande används. Teorin säger att det optimala incitamentet kan ge värdefullafördelar för de inblandade parterna eftersom det syftar till att på ett effektivt sätt fördelaprojektrisken mellan dem samtidigt som agenten får rätt incitament att arbeta mer effektivt föratt sänka kostnaderna och leverera högkvalitativa tjänster eller varor.
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Women´s Investment Behaviour A Study of Female Investment Behaviour Across DemographicsWongla, Intira, Hamrin, Agnes January 2024 (has links)
The purpose of this study is to examine the investment behaviour of women during the current recession and how demographic factors impact psychological biases related to investment behaviour. This research aims to examine the impact of age, marital status, education, income, cultural background and financial literacy on various biases such as overconfidence, confirmation bias, herding behaviour, representativeness bias, anchoring bias, risk- and loss aversion. A questionnaire was conducted to collect data, resulting in a dataset of 558 observations. Using a deductive approach, based on theories of thirty-six hypotheses was tested using ordered logistic regression analysis. The primary findings revealed multiple connections between the demographic profiles of female investors and their investment behaviours, concerning psychological biases. Furthermore, this paper contributes to the ongoing debate about the relationship between investment behaviour and economic recession and provides stakeholders with valuable insights to tailor their communications and strategies to engage female investors. By analysing existing behavioural finance theories and empirical data, the study aims to improve understanding of women's investment preferences and attitudes across different demographic groups. Finally, the study aims to increase women's interest in managing their wealth and improving their financial decisions.
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Fonctions d’utilité dépendantes des états de la nature, choix en incertitude et perception des risquesIngabire, Marie-Gloriose 04 1900 (has links)
Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.
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Six essays on stochastic and deterministic dynamic pricing and advertising modelsSchlosser, Rainer 03 June 2014 (has links)
Die kumulative Dissertation beschäftigt sich mit stochastischen und deterministischen dynamischen Verkaufsmodellen für langlebige sowie verderbliche Güter. Die analysierten dynamischen Modelle sind durch die Möglichkeit der simultanen Variation von Preis und Werbung in stetiger Zeit charakterisiert und folgen den aktuellen Entwicklungen der Dynamischen Preissetzung. Dabei steht die Berücksichtigung und Analyse von (i) Zeitinhomogenitäten, (ii) Adoptionseffekten, (iii) Oligopolwettbewerb und (iv) der Risikoaversion des Entscheiders im Zentrum der Arbeit. Für die Spezialfälle isoelastischer und exponentieller Nachfrage in Verbindung mit isoelastischer Werbewirkung gelingt es explizite Lösungen der optimalen Preis- und Werbekontrollen herzuleiten. Die optimal gesteuerten Verkaufsprozesse können analytisch beschrieben und ausgewertet werden. Insbesondere werden neben erwarteten Preis- und Restbestandsentwicklungen auch assoziierte Gewinnverteilungen untersucht und Sensitivitätsresultate hergeleitet. Darüber hinaus wird analysiert unter welchen Bedingungen monopolistische Strategien sozial effizient sind und welche Besteuerungs- und Subventionsmechanismen geeignet sind um Effizienz herzustellen. Die Ergebnisse sind in sechs Artikel gefasst und bieten ökonomische Einsichten in verschiedene praktische Verkaufsanwendungen, speziell im Bereich des elektronischen Handels. / The cumulative dissertation deals with stochastic and deterministic dynamic sales models for durable as well as perishable products. The models analyzed are characterized by simultaneous dynamic pricing and advertising controls in continuous time and are in line with recent developments in dynamic pricing. They include the modeling of multi-dimensional decisions and take (i) time dependencies, (ii) adoption effects (iii), competitive settings and (iv) risk aversion, explicitly into account. For special cases with isoelastic demand functions as well as with exponential ones explicit solution formulas of the optimal pricing and advertising feedback controls are derived. Moreover, optimally controlled sales processes are analytically described. In particular, the distribution of profits, the expected evolution of prices as well as inventory levels are analyzed in detail and sensitivity results are obtained. Furthermore, we consider the question whether or not monopolistic policies are socially efficient; in special cases, we propose taxation/subsidy mechanisms to establish efficiency. The results are presented in six articles and provide economic insights into a variety of dynamic sales applications of the business world, especially in the area of e-commerce.
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The impact of inequity aversion on relational incentive contractsKragl, Jenny 18 June 2009 (has links)
Diese Dissertation enthält drei Aufsätze zur Theorie der Anreizsetzung bei nicht-verifizierbaren Leistungsmaßen. Untersuchungsgegenstand sind die Auswirkungen individueller Fairnesspräferenzen auf die Ausgestaltung und Eignung verschiedener Anreizmechanismen, welche in realen wirtschaftlichen Situationen Anwendung finden. Alle Arbeiten analysieren Umgebungen moralischen Risikos, in denen eine Firma zwei ungerechtigkeitsaverse Mitarbeiter beschäftigt, deren individuelle Arbeitsleistung zwar beobachtbar, jedoch nicht kontrahierbar ist. Der erste Aufsatz untersucht die Effekte von Ungerechtigkeitsaversion auf relationale Anreizverträge. Als Leistungsmaß eines Agenten dient sein individueller Beitrag zum Firmenwert. Abweichend von der Literatur zeigt sich, dass Ungerechtigkeitsaversion vorteilhaft sein kann: Für bestimmte Zinssätze können relationale Verträge mit neidischen Agenten profitabler sein, wenn sie nicht sogar nur mit solchen implementierbar sind. Der zweite Aufsatz vergleicht relationale Individual- und Gruppenbonusverträge. Durch das Vermeiden ungleicher Löhne sind letztere profitabler, solange sich die Firma keinem Glaubwürdigkeitsproblem gegenübersieht. Dies kann sich jedoch umkehren, da Individualboni vergleichsweise kleiner sind und somit die Selbstdurchsetzung des Vertrags fördern. Ursachen dafür sind das Vermeiden des Trittbrettfahrerproblems und die Anreizwirkung von Neid. Im dritten Aufsatz wird relationalen Individualbonusverträgen ein relatives Leistungsturnier gegenübergestellt. Im Gegensatz zum Bonusvertrag unterliegt das Turnier keiner Glaubwürdigkeitsbeschränkung. Dennoch ist ersteres Anreizschema profitabler, solange das Glaubwürdigkeitsproblem der Firma nicht zu groß ist. Dies liegt an der zwingenden Auszahlung ungleicher Löhne im Turnier und den daraus resultierenden hohen Kosten für Ungleichheitsprämien. Weiter wird für ein Beispiel gezeigt, dass die Zinsspanne, für die der Bonusvertrag das Turnier dominiert, im Neid der Agenten steigt. / This thesis consists of three self-contained essays that investigate the impact of fairness concerns among agents on the design of real-world incentive contracts used to mitigate moral-hazard problems under non-verifiable performance. All papers consider situations in which a firm employs two inequity averse workers whose individual performances are, albeit observable by the contracting parties, not contractible. The first paper studies the effects of inequity aversion on relational employment contracts. Performance is evaluated via an agent’s individual non-verifiable contribution to firm value. In contrast to the literature, we find that inequity aversion may be beneficial: In the presence of envy, for a certain range of interest rates relational contracts may be more profitable. For some interest rates reputational equilibria exist only with envious agents. In the second paper, I compare group to individual performance pay. Avoiding payoff inequity, the group bonus contract is superior as long as the firm faces no credibility problem. The individual bonus contract may, however, become superior due to two reasons: The group bonus scheme is subject to a free-rider problem requiring a higher incentive pay and impeding credibility of the firm. Moreover, with individual bonuses the firm benefits from the incentive-strengthening effect of envy, further softening the credibility constraint. The third paper contrasts a rank-order tournament with independent bonus contracts. Whereas the bonus scheme must be self-enforcing, the tournament is contractible. Yet the former incentive regime outperforms the latter as long as credibility problems are not too severe. This is due the fact that the tournament requires unequal pay across peers with certainty and thus imposes large inequity premium costs on the firm. For a simple example, I show that the more envious the agents are the larger is the range of interest rates for which the bonus scheme dominates the tournament.
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Essays in Information EconomicsWangenheim, Jonas von 23 August 2018 (has links)
Diese Dissertation besteht aus drei unabhängigen Artikeln in dem Forschungsfeld der Informationsökonomik. Ein wiederkehrendes Motiv in allen drei Artikeln ist die ambivalente Rolle von privater Information. In Kontrast zur klassischen Entscheidungstheorie, in der mehr Informationen Individuen niemals schlechter stellt, analysiere ich drei verschiedene Umgebungen, in denen mehr Konsumenteninformation die Konsumentenrente verringern kann. / This dissertation comprises three independent chapters in the field of information
economics. The recurrent theme of all three chapters is the ambiguous role of
information: While in standard decision theory additional information enables individuals
to weakly increase utility through making better choices, I analyze three
di erent environments in which more information to consumers may actually be
detrimental to consumer utility.
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Droits de propriété foncière, aversion au risque et performance des petits producteurs agricolesLawin, Kotchikpa Gabriel 08 August 2024 (has links)
Cette thèse examine d’une part, l’impact des droits de propriété foncière sur la performance des petits producteurs agricoles et d’autre part, le rôle de l’aversion au risque dans la diversification des cultures au niveau des exploitations agricoles. Elle est subdivisée en quatre chapitres. Le premier chapitre fait la revue critique des méthodes et résultats des études empiriques qui analysent l’impact des droits de propriété foncière sur la performance des petits producteurs agricoles des pays en développement. Il montre que les résultats des études empiriques antérieures sont contrastés quant aux effets réels du droit de propriété. L’hétérogénéité des résultats est liée à la fois aux techniques d’évaluation utilisées et au contexte local de gestion du système foncier. Toutefois, les résultats convergent vers une endogénéité entre le droit de propriété et la performance des producteurs dans les contextes où la gestion coutumière du foncier est prédominante. Le deuxième chapitre analyse l’impact des droits de propriété foncière sur l’adoption des innovations agro-environnementales. Il utilise la méthode d’appariement par score de propension pour sélectionner les observations ayant les mêmes caractéristiques observables pour tenir compte du biais de sélection sur les variables observables. Il se base ensuite sur le modèle d’effet de traitement endogène multinomial développé par Deb et Trivedi (2006) pour tenir compte de l’endogénéité entre le droit de propriété et l’adoption d’innovation agro-environnementale. Le chapitre utilise des données détaillées au niveau des parcelles collectées au Bénin sur un échantillon de 2 800 petits producteurs et 4 233 parcelles. Il montre que les petits producteurs adoptent plus intensément les innovations agro-environnementales sur les parcelles dont ils sont propriétaires en comparaison aux parcelles prêtées, louées ou en métayage. Le troisième chapitre utilise le modèle de sélection de Greene (2010) pour les fonctions stochastiques de frontière appliquée à une fonction de distance en output et en combinaison avec la méthode d’appariement pour analyser l’impact de la sécurité foncière sur l’efficacité technique des petits producteurs agricoles. Il utilise également la méthode non paramétrique DEA (méthode d’enveloppement des données) pour analyser l’effet de la sécurité foncière sur la productivité agricole et décomposer cet effet en écart d’efficacité technique et en écart technologique entre les propriétaires terriens et les non-propriétaires. En se basant sur les données d’enquête au Bénin, il montre que les non-propriétaires ont en moyenne un niveau d’efficacité technique plus élevé et sont plus productifs que les propriétaires terriens. Par contre, les propriétaires affichent un net avantage technologique. Le quatrième chapitre porte sur l’effet de l’aversion au risque sur la diversification des cultures chez les petits producteurs agricoles au Burkina Faso. Une expérience terrain sous forme de loterie a été conduite pour mesurer l’aversion au risque des producteurs. Trois indices de diversité spatiale adaptés de la littérature en économie de l’environnement ont été utilisés pour mesurer la diversification des cultures au niveau des exploitations agricoles. Les résultats montrent que l’aversion au risque a un effet négatif et significatif sur la diversification des cultures. Les producteurs averses au risque se concentrent plus sur la production des cultures traditionnelles moins risquées et à faible valeur marchande. / This thesis examines the impact of land property rights on the performance of smallholder farmers and the role of risk aversion in crop diversification at the farm level. The dissertation is structured in four chapters. The first chapter provides a literature review of the methods and results of empirical studies that analyze the impact of land property rights on the performance of smallholder farmers in developing countries. It shows that the results of previous empirical studies are mixed about the real effects of property rights. The heterogeneity of the results is related both to the evaluation techniques used and to the local context of the tenure system’s management. However, the results converge towards an endogeneity between the property rights and the performance of smallholder farmers in contexts where customary land management is predominant. The second chapter analyzes the impact of land tenure differences on the adoption of agri-environmental innovations. It uses the propensity score matching method to select observations with the same observable characteristics to account for selection bias stemming from observed variables. In addition, possible self-selection arising from unobserved variables is addressed using a multinomial endogenous treatment effect model developed by Deb and Trivedi (2006). The chapter uses detailed cross-sectional plot-level dataset collected in Benin and covering a sample of 2,800 smallholder farmers and 4,233 plots. The results indicate that the intensity of the adoption of agri-environmental practices is consistently higher on owned plots than borrowed, rented or sharecropped plots. The third chapter uses the sample selection model introduced by Greene (2010) in stochastic frontier functions applied to a distance function in output and in combination with the matching method to analyze the impact of land security on technical efficiency of smallholder farmers in Benin. It also uses the non-parametric DEA (Data Envelopment Analysis) to analyze the effect of land tenure on agricultural productivity and to decompose this effect into a technical efficiency gap and technological differential between landowners and non-owners. The results show that non-owners are on average more productive than landowners because of their greater technical efficiency, while landowners have a technological advantage. The fourth chapter examines the effect of risk aversion on crop diversification among smallholder farmers in Burkina Faso. A field experiment in a form of lottery was conducted to measure producers' risk aversion. To measure crop diversification, we use three indices of spatial diversity in crop species adapted from the ecological economics literature. The results show that risk aversion has a negative and significant effect on crop diversification. Risk-averse producers focus more on the production of traditional, less risky and low market value crops.
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Théorie des options et fonctions d'utilité : stratégies de couverture en présence des fluctuations non gaussiennes / Options theory and utility functions : hedging strategies in the presence of non-gaussian fluctuationsHamdi, Haykel 04 March 2011 (has links)
L'approche traditionnelle des produits dérivés consiste, sous certaines hypothèses bien définies, à construire des stratégies de couverture à risque strictement nul. Cependant,dans le cas général ces stratégies de couverture "parfaites" n'existent pas,et la théorie doit plutôt s'appuyer sur une idée de minimisation du risque. Dans ce cas, la couverture optimale dépend de la quantité du risque à minimiser. Dans lecadre des options, on considère dans ce travail une nouvelle mesure du risque vial'approche de l'utilité espérée qui tient compte, à la fois, du moment d'ordre quatre,qui est plus sensible aux grandes fluctuations que la variance, et de l'aversion aurisque de l'émetteur d'une option vis-à-vis au risque. Comparée à la couverture endelta, à l'optimisation de la variance et l'optimisation du moment d'ordre quatre,la stratégie de couverture, via l'approche de l'utilité espérée, permet de diminuer lasensibilité de la couverture par rapport au cours du sous-jacent. Ceci est de natureà réduire les coûts des transactions associées / The traditional approach of derivatives involves, under certain clearly defined hypothesis, to construct hedging strategies for strictly zero risk. However, in the general case these perfect hedging strategies do not exist, and the theory must be rather based on the idea of risk minimization. In this case, the optimal hedging strategy depends on the amount of risk to be minimized. Under the options approach, we consider here a new measure of risk via the expected utility approach that takes into account both, the moment of order four, which is more sensitive to fluctuations than large variance, and risk aversion of the investor of an option towards risk. Compared to delta hedging, optimization of the variance and maximizing the moment of order four, the hedging strategy, via the expected utilitiy approach, reduces the sensitivy of the hedging approach reported in the underlying asset price. This is likely to reduce the associated transaction costs.
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期貨最適避險策略之研究--國際金融性期貨商品實證分析鄭適薰, ZHENG,SHI-XUN Unknown Date (has links)
一、研究動機與目的
由於國際經濟體系日趨複雜,持有資產的不確定性因而增加,投資者為了避免因為資
產報酬過大的波動而造成損失,紛紛尋求迴避風險的工具。而期貨由於具備了高度流
動性,融通功能的保證金制度及公正的中介機構等優點,使其產品種類及交易量日益
擴大,提供了金融資產持有者良好的避險管道。
本研究探討金融性期貨商品在各種避險期間長度及不同到期日的期貨契約,降低風險
的程度是否有差異,並就各避險策略理論,比較其績效。
二、研究期間與樣本。
本研究由華爾街日報及偷敦金融時報抄錄由1988年 1月到1990年1 月共108 週,每週
三金融性商品現貨及期貨收盤價格。包括黃金、英鎊、日圓、西德馬克、瑞士法郎及
S & P 500 NYSE股價指數和T-Bill Euro Dollar利率等九種。
三、研究方法。
主要比較以下三種避險策略降低風險的程度,並研究以期貨避險時,是否愈早簽訂契
約或選擇到期日距今較遠的契約愈能降低風險。
1.天真法則 (Naive Approch)
該策略假設任何資產的現貨與期貨價格變動方向一致且幅度相同。於是為了避免資產
因為價格波動造成損失,投資者的避險策略應該是分別持有數量相同但方向相反的現
貨與期貨部位(position)。如此現貨資產與期貨資產的損益可完全抵消,若不計交易
成本,則造成損失的可能性為零。
2.最小變異數法則 (Minimum Variance Approach)
該法則認為,現貨與期貨價格同方向且等幅度變動的假設並不合理,而將現貨與期貨
所持有的部位視為資產組合 (portfolio),此資產組合價格的變異數視為風險;求出
使該資產組合風險最小的期貨部位。期貨相對現貨的持有比值就是最適避險比率,以
此比率構成資產組合風險最小。
3.風險迴避法則(Risk Aversion Approach)
該法則引用普雷特-亞羅(Pratt-Arrow) 絕對風險迴避的觀念,尋求報酬和風險間的
替代關係,在報酬不為負的要求下,求出使資產組合風險最小的避險比率。此法則由
於衡量的標準更為嚴格,故計算亦較繁複。
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Maximising the effectiveness of aerial 1080 control of possums (Trichosurus vulpecula)Morgan, David R. January 2004 (has links)
Aerial control using 1080 (sodium monofluoroacetate) baits is widely used in New Zealand for the control of introduced brushtail possums (Trichosurus vulpecula), with the aim of protecting national conservation and agricultural values from these damaging pests. This thesis integrates research, completed over 25 years, that was motivated by growing recognition in the 1970s of the extent of possum impacts and the need to improve the effectiveness and efficiency of the control operation. Field research assessed the palatability of three types of cereal-based pellet baits and carrot baits in different regions, habitat types and seasons. Palatability was assessed by the consumption of the different bait types presented independently of each other on 15-30 plots, with rotation of bait types at plots on successive nights to provide equal exposure to each bait type. There was regional variation in possums' bait preferences, possibly reflecting genotypic differences, whereas seasonal variation was less evident. Carrot bait was preferred or equally preferred to cereal bait in 14 out of 20 field trials. The proportion of possums eating baits was then investigated by, firstly, developing a technique for tracing bait acceptance using rhodamine B, a UV-fluorescent dye. In four field trials, more than 95% of possums accepted three types of dye-marked bait, eliminating bait refusal as a major reason for low kills in winter control operations. In a fifth trial, conducted in summer, only 68% of possums accepted bait suggesting that seasonal availability of favoured foods may influence bait acceptance. Since possums must encounter baits before deciding whether to eat them, field studies were undertaken to assess the coverage achieved in normal aerial baiting operations. Large gaps, up to 400 m in width, were often found between baiting swaths; these could allow some possums to survive. A controlled field experiment, using acceptance of rhodamine-dyed bait as a measure of effectiveness, showed that bait distribution was least accurate where flight paths were not marked. Where gaps of 100 m between flight paths were deliberately created, bait acceptance was slower and less than where coverage was complete. Sowing baits at 3 kg/ha was as effective as at 10 kg/ha, indicating the potential for substantially reducing operational costs by using machinery capable of faultlessly distributing baits at low rates. Navigational guidance systems were evaluated and found to improve the accuracy of bait distribution. During 1993-1997, when a lower sowing rate of 5 kg/ha was adopted operationally by regional managers, control effectiveness was unchanged but annual savings of around $9 million accrued. Because of the lack of suitable sowing machinery, a bucket was developed to permit faultless distribution of baits at lower rates, demonstrating the possibility of yet further cost-savings. The possibility of seasonal food availability affecting bait acceptance was investigated in three different forest habitats. Dyed baits were aerially distributed on 100 ha at each site in each season over two years. In each trial, fat-based condition indices of possums were calculated and the abundance of possum-preferred plant foods described. Bait acceptance was consistently high (85-100%) in the 24 trials, and was not influenced by either condition or availability of preferred foods. It seems likely that seasonal variation in operational effectiveness is caused by either the availability of sharply seasonal, scarce foods that possums may feed on intensively for brief periods, or by warmer temperatures that render 1080 less effective. The influence of 1080 on acceptance of (rhodamine-dyed) baits was investigated in a field trial. Examination of possums for dye-marking showed that 25% of possums refused to eat either a lethal quantity of bait or any bait at all, compared with 98% of possums eating non-toxic bait. This indicated that 1080 is aversive to possums, which is a potential major reason for their surviving control operations. Pen trials were therefore conducted to further examine the problem and to seek solutions. Toxic carrot baits were rejected by 27.5% of possums, equally by smell and taste aversion, whereas toxic cereal pellets were rejected by 34%, mainly by taste aversion. Orange and cinnamon were shown to be among the most preferred of 42 flavours tested and, when applied to toxic baits, 1080 was effectively masked. Bait refusal was reduced to ≤7%, the same as that recorded for possums presented with flavoured non-toxic baits. For long-term control of possum populations, aerial 1080 baiting can be used sequentially with other poisoning methods. However, the compatibility of these methods is dependent on the likelihood of possums developing bait shyness if sublethally dosed. Studies were therefore conducted to characterise and compare the four main toxicants used (1080, cyanide, cholecalciferol and brodifacoum) for induction and mitigation of bait shyness. Shyness was induced in approximately 80% of possums sublethally dosed with cyanide, 60% with 1080, 20% with cholecalciferol, and 0% with brodifacoum. Cyanide and 1080 shyness were found to persist in many possums for at least 12 and 24 months, respectively. Use of alternative bait types, and of baits containing an alternative slow-acting toxin (brodifacoum) were shown to be effective ways of overcoming shyness. This, and other related research, is reviewed to provide operational specifications that maximise the likelihood that all targeted possums will (i) encounter bait, (ii) eat it, and (iii) die. The likely future use of aerial 1080 baiting is described and the technological, economic, environmental and social constraints on its sustainability are discussed. Finally, the uptake of the research by possum managers is considered, and areas identified in the thesis where information is incomplete are summarised as prioritised topics for further research.
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