Less is more: rarity trumps quality in luxury markets

The international market for luxury goods has almost doubled since 1990, with a worldwide increase of 10% annually. This trade is fuelled by a great deal of legally and illegally exploited wildlife species, putting enormous pressure on many of them, with potentially irreversible consequences. The dramatic decline of sturgeon populations exploited for their caviar, is a good example: all 27 species are threatened and the most coveted are on the verge of extinction. We aim to identify the mechanism responsible for the continued overexploitation of sturgeon species, despite caviar's ever-increasing price and the imminent loss of these species. Here, we demonstrate consumer preference for rarity over intrinsic quality: customers tasting two caviar samples more often chose the one they thought was rare, although both were identical. In a game theory model, we demonstrate that the most rational behaviour is to rush to consume rare species, even though this precipitates their extinction. We conclude that the human predisposition to place exaggerated value on rarity probably drives the entire market for luxury goods from reptile skins to exotic woods. Our findings suggest that allowing low levels of legal trade will exacerbate the arbitrary value of rare species and thereby stimulate demand. Only a total ban on trade from the wild (with very strict controls) combined with strong support for farmed equivalents will protect rare species

Pigeons home faster through polluted air.

Air pollution, especially haze pollution, is creating health issues for both humans and other animals. However, remarkably little is known about how animals behaviourally respond to air pollution. We used multiple linear regression to analyse 415 pigeon races in the North China Plain, an area with considerable air pollution, and found that while the proportion of pigeons successfully homed was not influenced by air pollution, pigeons homed faster when the air was especially polluted. Our results may be explained by an enhanced homing motivation and possibly an enriched olfactory environment that facilitates homing. Our study provides a unique example of animals' response to haze pollution; future studies are needed to identify proposed mechanisms underlying this effect

Comparison of colony dynamics in native and invasive ant species

Trabalho de mestrado integrado em Medicina (Geriatria/Otorrinolaringologia), apresentado á Faculdade de Medicina da Universidade de CoimbraA presbiacusia, ou perda auditiva relacionada com a idade, trata-se, portanto, de uma doença degenerativa auditiva neurossensorial com a presença de alterações tanto no ouvido e sistema vestíbulo-coclear como no sistema nervoso central. A etiologia é ainda pouco compreendida, havendo associações a hereditariedade, fatores ambientais, patologias prévias, radicais livres e dano ao ADN mitocondrial, e que se apresenta com potenciais implicações na qualidade de vida dos doentes, com o aumento da dificuldade de comunicação com o meio social, levando a distúrbios como depressão, isolamento social, dependência e frustração e que apresenta adicionalmente consequências na sua saúde, uma vez que impede o diálogo entre o doente e o seu meio envolvente, quer este seja o seu meio social imediato, com o maior isolamento social que daí advém, o seu ambiente laboral, com a diminuição da sua prestação e rendimento, ou em ambiente de cuidados de saúde, impedindo o fornecimento de cuidados necessários ao doente, não levando à melhoria da sua condição física, antes pelo contrário. Esta patologia tem implicações não só para o doente, mas também para as pessoas com quem ele tem convivência direta. Apesar de haver alguma melhoria com a utilização de aparelhos auditivos, esta não passa de uma solução provisória e, portanto, têm de existir outras estratégias a ser usadas. Este é um problema crescente e cada vez mais importante, uma vez que observamos um envelhecimento da população com o aumento associado de doenças degenerativas, tendo isto implicação com aumento de encargos com a saúde e diminuição da qualidade de vida da população. Com o objetivo de minorar o impacte desta patologia na sociedade, este artigo visa a revisão da literatura com a ênfase e proposta de estratégias já existentes ou congruentes com o atual conhecimento acerca desta patologia, respetivamente, passíveis de João Filipe Martins Março, 2015 Presbiacusia: Dificuldades na Comunicação e Estratégias a Aplicar 3 ser implementadas nos diferentes meios frequentados pelos doentes e que permitam que a comunicação entre o doente e as pessoas com quem ele contacta seja facilitadaPresbycusis or age related hearing loss is an auditory neurosensory degenerative condition linked to changes in both the inner ear, namely the cochlea, and the central nervous system. Although its causes are as of yet not fully known, some associations have been made with genetic factors, environmental and pathologic aggressions, oxidizing radicals and damage to mitochondrial DNA. This condition is aligned with a serious impact in the patient’s quality of life, due to the communication barrier that it poses, leading to such disorders as depression, social isolation, dependency and frustration and can, furthermore, impact his health even deeper, because it hinders speech and it hinders the dialog within his household, his workplace and with healthcare providers, thus lowering the patient’s productivity and overall health status, with both the direct and indirect costs that ensues. This condition affects not only the patient, but also those with whom he most closely relates. In that manner, rehabilitation using hearing aids seams promising, but, as of now, it exists as just a temporary solution and therefore other strategies are to be implemented. This creates a growing issue, as seen by the increased aging of the population and the increase of degenerative diseases that goes hand in hand with it, namely age related hearing loss, with the associated healthcare costs and quality life years lost. With the goal to reduce the impact this condition has and will have in modern day society, this paper aims to review the current literature, focusing mainly on already existing rehabilitation protocols and, through its study, the proposal of possible new ones, which can later be thoroughly tested, that will enable patients with this condition to live a longer, fuller lif

A dynamical trichotomy for structured populations experiencing positive density-dependence in stochastic environments

Positive density-dependence occurs when individuals experience increased survivorship, growth, or reproduction with increased population densities. Mechanisms leading to these positive relationships include mate limitation, saturating predation risk, and cooperative breeding and foraging. Individuals within these populations may differ in age, size, or geographic location and thereby structure these populations. Here, I study structured population models accounting for positive density-dependence and environmental stochasticity i.e. random fluctuations in the demographic rates of the population. Under an accessibility assumption (roughly, stochastic fluctuations can lead to populations getting small and large), these models are shown to exhibit a dynamical trichotomy: (i) for all initial conditions, the population goes asymptotically extinct with probability one, (ii) for all positive initial conditions, the population persists and asymptotically exhibits unbounded growth, and (iii) for all positive initial conditions, there is a positive probability of asymptotic extinction and a complementary positive probability of unbounded growth. The main results are illustrated with applications to spatially structured populations with an Allee effect and age-structured populations experiencing mate limitation

Climate Change May Boost the Invasion of the Asian Needle Ant

Following its introduction from Asia to the USA, the Asian needle ant (Pachycondyla chinensis) is rapidly spreading into a wide range of habitats with great negative ecological affects. In addition, the species is a concern for human health because of its powerful, sometimes deadly, sting. Here, we assessed the potential of P. chinensis to spread further and to invade entirely new regions. We used species distribution models to assess suitable areas under current climatic conditions and in 2020, 2050 and 2080. With a consensus model, combining five different modelling techniques, three Global Circulation (climatic) Models and two CO2 emission scenarios, we generated world maps with suitable climatic conditions. Our models suggest that the species currently has a far greater potential distribution than its current exotic range, including large parts of the world landmass, including Northeast America, Southeast Asia and Southeast America. Climate change is predicted to greatly exacerbate the risk of P. chinensis invasion by increasing the suitable landmass by 64.9% worldwide, with large increases in Europe (+210.1%), Oceania (+75.1%), North America (+74.9%) and Asia (+62.7%). The results of our study suggest P. chinensis deserves increased attention, especially in the light of on-going climate change. © 2013 Bertelsmeier et al.published_or_final_versio

Fatal attraction: rare species in the spotlight

The exploitation of rare and endangered species can end in the species's extinction because the increased value people associate with rarity increases the economic incentive to exploit the last individuals, creating a positive feedback loop. This recently proposed concept, called the anthropogenic Allee effect (AAE), relies on the assumption that people do value rarity, but this remains to be established. Moreover, it also remains to be determined whether attraction to rarity is a trait confined to a minority of hobbyists (e.g. wildlife collectors, exotic pet owners) or characteristic of the general public. We estimated how much the general public valued rare species compared with common ones, using five different metrics related to personal investment: time spent, physical effort, unpleasantness, economic investment and risk. We surveyed the visitors of a zoo. To see the rare species, the visitors to the zoo invested more time in searching and contemplation, they were ready to expend more physical effort, they tolerated more unpleasant conditions, they were willing to pay more and, finally, they risked more to obtain (steal) a rare species. Our results provide substantial evidence of how the general public places more value on rare species, compared with common species. This confirms the AAE as an actual process, which in addition concerns a large part of the population. This has important consequences for the conservation of species that are rare now, or that could become so in the future

Discovery-dominance trade-off among widespread invasive ant species.

Ants are among the most problematic invasive species. They displace numerous native species, alter ecosystem processes, and can have negative impacts on agriculture and human health. In part, their success might stem from a departure from the discovery-dominance trade-off that can promote co-existence in native ant communities, that is, invasive ants are thought to be at the same time behaviorally dominant and faster discoverers of resources, compared to native species. However, it has not yet been tested whether similar asymmetries in behavioral dominance, exploration, and recruitment abilities also exist among invasive species. Here, we establish a dominance hierarchy among four of the most problematic invasive ants (Linepithema humile, Lasius neglectus, Wasmannia auropunctata, Pheidole megacephala) that may be able to arrive and establish in the same areas in the future. To assess behavioral dominance, we used confrontation experiments, testing the aggressiveness in individual and group interactions between all species pairs. In addition, to compare discovery efficiency, we tested the species' capacity to locate a food resource in a maze, and the capacity to recruit nestmates to exploit a food resource. The four species differed greatly in their capacity to discover resources and to recruit nestmates and to dominate the other species. Our results are consistent with a discovery-dominance trade-off. The species that showed the highest level of interspecific aggressiveness and dominance during dyadic interactions