Direct empirical estimation of efficiency in secondary materials markets: The case of steel scrap

The U.S. steel scrap market is used as a test case for a method of directly estimating the efficiency of recycled materials markets. Such markets are examples of commodity markets for which there is no organized futures exchange. If, as widely held, futures markets enhance market efficiency we attempt to answer the question of how recycled commodity markets suffer, if at all, from the lack of a futures exchange. In this paper econometric modeling and time-series methods produce robust estimates of market efficiency as measured by the percent of traders that possess the latest information concerning market disequilibrium. Based on the empirical results it would appear that on a monthly basis the steel scrap industry distributes its commodities in an economically efficient manner and therefore would derive little benefit from an organized futures exchange.     

The economics of mutualisms: optimal utilization of mycorrhizal mutualistic partners by plants

Can choice of mutualistic partners and the degree of their utilization determine (1) mutualistic partner coexistence, (2) relative abundance of mutualistic partners, and (3) environment-dependent changes in relative abundance? We investigate these questions in the context of the plant-mycorrhizal fungal mutualism by building a biological market model potentially applicable to other mutualisms as well. We examine the situation where a single plant selectively utilizes member(s) of a group of ectomycorrhizal potential trading partners. Under biologically realistic circumstances, the plant may simultaneously utilize multiple partners, its degree of utilization determining the community structure of the fungi. If utilization of multiple partners is optimal, the marginal cost of acquiring additional nitrogen from every trading partner must be equal while the marginal cost of acquiring it from any unutilized partner must be larger. Because the plant's nitrogen demand is light dependent, the composition of the fungal species among its trading partners changes along light-availability gradients. We discuss the design of an experiment to test the key prediction of our model, the equalization of marginal cost.     

Rank-related partner choice in the fission–fusion society of the spotted hyena (<Emphasis Type="Italic">Crocuta crocuta</Emphasis>)

When social partners vary in their relative value, individuals should theoretically initiate partnerships with conspecifics of the highest value. Here, we tested this prediction in a wild population of spotted hyenas (Crocuta crocuta). Crocuta live in complex, fission–fusion societies structured by dominance hierarchies in which individuals vary greatly in their value as social companions. Because patterns of association among Crocuta reflect social preferences, we calculated association indices (AIs) to examine how social rank influences intrasexual partner choice among unrelated adults of both sexes. The highest-ranking individuals were generally most gregarious in both sexes. Females associated most often with dominant and adjacent-ranking females. Females joined subgroups based on the presence of particular conspecifics such that subordinates joined focal females at higher rates than did dominants. Dominants benefit from associations with subordinates by enjoying priority of access to resources obtained and defended by multiple group members, but the benefits of these associations to subordinates are unknown. To investigate this, we tested three hypotheses suggesting how subordinates might benefit from rank-related partner choice among unrelated females. We found that subordinates who initiated group formation benefited by gaining social and feeding tolerance from dominants. However, rates at which dominants provided coalitionary support to subordinates did not vary with AIs. Overall, our data resemble those documenting patterns of association among cercopithecine primates. We consider our results in light of optimal reproductive skew theory, Seyfarth’s rank attractiveness model, and biological market theory. Our data are more consistent with the predictions of Seyfarth’s model and of biological market theory than with those of skew theory.     

The influence of potential reproductive rate and variation in mate quality on male and female choosiness in the sand goby, Pomatoschistus minutus

Recent models of choosiness in mate choice have identified two particularly important factors: the potential reproductive rate (PRR) of the choosing sex relative to that of the chosen sex, and the variation in quality of potential mates. This experimental study tested how these factors affected choosiness in male and female sand gobies, Pomatoschistus minutus. We manipulated relative PRR by means of water temperature, and mate quality by means of body length. The choosing male or female was offered a choice between two mates with either a small or a large difference in body length representing a small or a large variation in mate quality. Choosiness was measured as (1) preference for the larger mate, and (2) as whether or not spawning occurred with the smaller mate, while the larger mate was visible but screened off. We found that females preferred large males, and that their level of choosiness was affected by variation in male quality, but not by their own relative PRR. Males, on the other hand, seemed unselective in all treatments and were in general more likely than females to spawn with their provided partner. This suggests that in the sand goby, variation in male mate quality has a greater influence than relative PRR on facultative changes in female choosiness. However, a general difference in PRR between males and females may be one important factor explaining the observed sex difference in choosiness. Received: 17 April 2000 / Revised: 24 June 2000 / Accepted: 17 July 2000     

Temporal changes in demand for and supply of nests in red bishops (Euplectes orix): dynamics of a biological market

The red bishop (Euplectes orix) is a highly polygynous and colonial weaverbird. Males construct several nests within their territories to which they try to attract females, and females are solely responsible for incubation and raising offspring. In this paper, we describe the characteristics of the red bishop’s mating system as a biological market and investigate the role of nests built by males as a traded commodity in a mating market. As timing of breeding in red bishops in arid and semi-arid zones depends on rainfall patterns which are often unpredictable, there are temporal changes in demand for and supply of nests within a breeding season, with breeding activities of males and females being highly synchronised. We found that males increased their nest-building speed with increased female breeding activity independently of rainfall, indicating that supply follows demand in this mating market. The supply of nests was always larger than the demand for nests. Construction costs for nests increased with demand for nests as indicated by shorter nest-building duration and shorter building delays between two consecutively built nests at times of high breeding activity. Males as a trading class are chosen according to the age of their nests offered, with young nests having a higher probability of being accepted by females. Furthermore, female choosiness with regard to nest age decreased when their own market value decreased, as predicted by biological market theory. The temporal changes of breeding activity together with the female preference for young and fresh nests require that males quickly adjust nest-building activity to varying female demand for new nests. However, males with a better adjustment of building speed to female breeding activity did not gain higher mating success.     

Structure and Operation of a Bushmeat Commodity Chain in Southwestern Ghana

Abstract:  The bushmeat trade is perceived as a major threat to wild animal populations in the tropics. Little is known of how the trade is organized, however, or of the actors involved in it, impeding the development of effective conservation policy. We investigated the structure and operation of a bushmeat commodity chain in West Africa that supplies a typical urban market, the city of Takoradi in southwestern Ghana. Data were collected from January through February 2000, describing 2430 bushmeat transactions encompassing 17 different taxa from 70 different actors, through a combination of direct observation and semistructured interviews. Five different types of actor traded along the commodity chain: commercial hunters, farmer hunters, wholesalers, market traders, and chopbar (cafe) owners. Bushmeat was traded freely among all these actors, although the primary trade route for terrestrial mammals was from commercial hunters via wholesalers to chopbars. In contrast, invertebrates were only traded by farmer hunters, market traders, and chopbars. Wholesalers captured the largest per capita share of the market (4% of all sales were handled by each wholesaler), whereas the most important vendors were chopbars, which as a group made 85% of all bushmeat sales to the public. Variation in the price of bushmeat was largely explained by transport costs and taste preferences. Transport costs were most significant for hunters and greatest on long journeys involving large loads. Nevertheless, hunters obtained the greatest income per kilogram of bushmeat sold of all actor groups. Our results suggest that there is no single best entry point along the bushmeat commodity chain for conservation intervention. On the contrary, the successful monitoring and management of the bushmeat trade is likely to require a multiactor approach that encompasses most or all actor groups.     

Use of Market Data to Assess Bushmeat Hunting Sustainability in Equatorial Guinea

Abstract: Finding an adequate measure of hunting sustainability for tropical forests has proved difficult. Many researchers have used urban bushmeat market surveys as indicators of hunting volumes and composition, but no analysis has been done of the reliability of market data in reflecting village offtake. We used data from urban markets and the villages that supply these markets to examine changes in the volume and composition of traded bushmeat between the village and the market (trade filters) in Equatorial Guinea. We collected data with market surveys and hunter offtake diaries. The trade filters varied depending on village remoteness and the monopoly power of traders. In a village with limited market access, species that maximized trader profits were most likely to be traded. In a village with greater market access, species for which hunters gained the greatest income per carcass were more likely to be traded. The probability of particular species being sold to market also depended on the capture method and season. Larger, more vulnerable species were more likely to be supplied from less‐accessible catchments, whereas there was no effect of forest cover or human population density on probability of being sold. This suggests that the composition of bushmeat offtake in an area may be driven more by urban demand than the geographic characteristics of that area. In one market, traders may have reached the limit of their geographical exploitation range, and hunting pressure within that range may be increasing. Our results demonstrate that it is possible to model the trade filters that bias market data, which opens the way to developing more robust market‐based sustainability indices for the bushmeat trade.     

Reciprocity and trades in wild West African chimpanzees

Why do animals help other individuals and provide benefits to the recipient, sometimes at personal cost? In this study, we aim to determine if some of the helpful behaviors observed in a group of wild chimpanzees (Taï chimpanzee group, Côte d'Ivoire, West Africa) are exchanged among individuals resulting in a net benefit for both participants. We adopted an inclusive view of exchanges by considering that all commodities (i.e., social behaviors as grooming, sex, support, as well as resources, such as meat) can be exchanged. This would result in “market” type social interactions in which debts of one commodity can be met by giving the same or other commodities. We investigated whether both in-kind exchanges and trades of commodities occurred. The Taï chimpanzees reciprocated the amount of grooming they received and were more likely to give support in agonistic conflicts to those who also supported them. In addition, they traded support for meat and meat for sex. Both male and female chimpanzees exchanged many different commodities, which seemed to result in long-term balanced relationships. Our results suggest that wild chimpanzees rely on other group members to obtain many of the important commodities they need.     

The roles of sensory traps in the origin, maintenance, and breakdown of mutualism

Sensory traps are signal mimics that elicit out-of-context behaviors by exploiting the adaptive, neural responses of signal receivers. Sensory traps have long been invoked in studies of mate and prey attraction, but the possible roles of sensory traps in mutualisms (cooperation between species) have yet to be thoroughly examined. Our review identifies four candidate roles for sensory traps in the evolution of mutualistic interactions: reassembly, error reduction, enforcement, and cost reduction. A key consequence of sensory traps is that they limit the applicability of partner choice and biological market models of mutualism. We conclude by suggesting that an important research topic in the evolution of cooperation should be to identify any mechanisms that increase the truthfulness of communication between cooperating species.     

Effects of Dam‐Induced Landscape Fragmentation on Amazonian Ant–Plant Mutualistic Networks

Mutualistic networks are critical to biological diversity maintenance; however, their structures and functionality may be threatened by a swiftly changing world. In the Amazon, the increasing number of dams poses a large threat to biological diversity because they greatly alter and fragment the surrounding landscape. Tight coevolutionary interactions typical of tropical forests, such as the ant–myrmecophyte mutualism, where the myrmecophyte plants provide domatia nesting space to their symbiotic ants, may be jeopardized by the landscape changes caused by dams. We analyzed 31 ant–myrmecophyte mutualistic networks in undisturbed and disturbed sites surrounding Balbina, the largest Central Amazonian dam. We tested how ant–myrmecophyte networks differ among dam‐induced islands, lake edges, and undisturbed forests in terms of species richness, composition, structure, and robustness (number of species remaining in the network after partner extinctions). We also tested how landscape configuration in terms of area, isolation, shape, and neighborhood alters the structure of the ant–myrmecophyte networks on islands. Ant–myrmecophytic networks were highly compartmentalized in undisturbed forests, and the compartments had few strongly connected mutualistic partners. In contrast, networks at lake edges and on islands were not compartmentalized and were negatively affected by island area and isolation in terms of species richness, density, and composition. Habitat loss and fragmentation led to coextinction cascades that contributed to the elimination of entire ant–plant compartments. Furthermore, many myrmecophytic plants in disturbed sites lost their mutualistic ant partners or were colonized by opportunistic, nonspecialized ants. Robustness of ant–myrmecophyte networks on islands was lower than robustness near lake edges and in undisturbed forest and was particularly susceptible to the extinction of plants. Beyond the immediate habitat loss caused by the building of large dams in Amazonia, persistent edge effects and habitat fragmentation associated with dams had large negative effects on animal–plant mutualistic networks. Efectos de la Fragmentación del Paisaje Inducida por Presas sobre Redes Mutualistas Hormiga‐Planta Amazónicas     

A dynamic simulation model to support reduction in illegal trade within legal wildlife markets

Sustainable wildlife trade is critical for biodiversity conservation, livelihoods, and food security. Regulatory frameworks are needed to secure these diverse benefits of sustainable wildlife trade. However, regulations limiting trade can backfire, sparking illegal trade if demand is not met by legal trade alone. Assessing how regulations affect wildlife market participants’ incentives is key to controlling illegal trade. Although much research has assessed how incentives at both the harvester and consumer ends of markets are affected by regulations, little has been done to understand the incentives of traders (i.e., intermediaries). We built a dynamic simulation model to support reduction in illegal wildlife trade within legal markets by focusing on incentives traders face to trade legal or illegal products. We used an Approximate Bayesian Computation approach to infer illegal trading dynamics and parameters that might be unknown (e.g., price of illegal products). We showcased the utility of the approach with a small-scale fishery case study in Chile, where we disentangled within-year dynamics of legal and illegal trading and found that the majority (∼77%) of traded fish is illegal. We utilized the model to assess the effect of policy interventions to improve the fishery's sustainability and explore the trade-offs between ecological, economic, and social goals. Scenario simulations showed that even significant increases (over 200%) in parameters proxying for policy interventions enabled only moderate improvements in ecological and social sustainability of the fishery at substantial economic cost. These results expose how unbalanced trader incentives are toward trading illegal over legal products in this fishery. Our model provides a novel tool for promoting sustainable wildlife trade in data-limited settings, which explicitly considers traders as critical players in wildlife markets. Sustainable wildlife trade requires incentivizing legal over illegal wildlife trade and consideration of the social, ecological, and economic impacts of interventions.     

Compliance with ivory trade regulations in the United Kingdom among traders

Global demand for elephant ivory is contributing to illegal poaching and significant decline of African elephant (Loxondonta africana) populations. To help mitigate decline, countries with legal domestic ivory markets were recommended by the Convention on International Trade in Endangered Species of Wild Fauna and Flora to close domestic markets for commercial trade. However, implementing stricter regulations on wildlife trade does not necessarily mean compliance with rules will follow. Using an online questionnaire, we examined the relationship between self-reported compliance with ivory trade regulations among 115 ivory traders in the United Kingdom and 4 dimensions (control, deterrence, legitimacy, and social norms) hypothesized to influence compliance with conservation regulations. Although most traders supported regulations, a large number did not always check that they comply with them when trading objects containing ivory. The main factors influencing compliance with ivory trade regulations were traders’ ability to comply and their perceptions of the regulations and punishments to deter illegal trade. These findings demonstrate the utility of conservation criminology to improve wildlife trade regulations and identify opportunities to reduce illegal ivory entering the market in the United Kingdom. Compliance could be improved by clearer regulations that facilitate easier detection of illegal ivory products and stronger prosecution of violations.     

Principles and processes for enhancing sustainable rural livelihoods: Collaborative learning in Uganda

Livelihood diversification is essential to food security and improved incomes for human development in African rural communities. Uganda's agrarian economy suffers from limited diversification, environmental degradation, low incomes, and multifaceted negative impacts of AIDS. Efforts to stimulate and support innovation in agricultural production technology, forms of social organization, and poor markets are essential elements in promotion of sustainable rural livelihoods. Iowa State University's Center for Sustainable Rural Livelihoods and its partner organizations are applying a multi-dimensional approach to engage Uganda farmers and rural leaders in community-based learning and capability strengthening. We describe the role played by livelihood diversification and explore the promotion of sustainable livelihoods through scholarship with praxis. Sustainable livelihoods concepts are examined as a means to better understand contemporary African rural development. We identify principles and processes critical to achieving sustainable livelihoods. Their application is highlighted based on our early collaborative experience, including a discussion of the complexities associated with entering into balanced partnerships required for a successful community-based program. We explore the value of social science perspectives and processes for strengthening rural development in developing countries.     

Volume and financial value of species traded in the medicinal plant markets of Gauteng,South Africa

The demand for traditional medicinal plants and products in South Africa has created an extensive cross-border industry involving thousands of harvesters and traders. The market values of individual taxa vary considerably. Pricing structures fluctuate between markets and over time as the cost of harvesting species varies depending on a gatherer's access to the resources and the proximity of markets to the harvesting sites. This paper estimates trade values, describes the prices paid for 22 plant resources, investigates pricing structures relative to the mass/volume sold and the factors that influence the market price for plants. There is an inverse and disproportionate relationship between the price per kilogram (R/kg) and mass of the product sold. The smaller the quantity sold, the higher the R/kg sale values are relative to sales of larger quantities. This relationship is evident in different plant part types (e.g. bark and bulbs), species and markets (shops and street markets). Given the high mass sold relative to the price, bulbs, like bark, have the lowest R/kg values compared to other products like roots, fruits and leaves. The prices paid for heavier/denser species is thus disproportionate to the mass sold. If the relative values are used as an indicator of plant vulnerability (assuming high values indicate greater vulnerability), then bias is created in favour of 'lighter' and less dense plant parts typically sold in small quantities because of the nature of the plant part and the manner in which it is marketed and required by customers.     

An Economic Assessment of Wildlife Farming and Conservation

Abstract:  The supply-side approach to conservation, as recommended by economists, prescribes the provision of cheap substitutes for wildlife commodities in an effort to lower the price of such commodities and reduce harvesting pressure. We developed a theoretical economic model to examine whether wildlife farming or ranching indeed contributes to conservation. We first present the naïve economic model that lends support to the supply-side approach. This model is incomplete because it fails to capture the fact that most wildlife markets are not perfectly competitive (instead, models are characterized by a small number of suppliers who have a certain degree of market power), which also implies that it fails to incorporate strategic interaction between suppliers. We then present an alternative model of the (illegal) wildlife trade that reflects imperfect competition and strategic interaction, and demonstrate that wildlife farming may stimulate harvesting (or poaching) rather than discourage it. By applying the model to the case of rhinoceros poaching and ranching, we demonstrate the potentially ambiguous outcomes of rhinoceros-ranching initiatives—wild rhinoceros stocks may recover or suffer from additional depletion, depending on key parameters and the type of competition on output markets. We also show that this type of ambiguity may be eliminated when policy makers restrict quantities of farmed output through a quota system; in that case, introducing wildlife farming will unambiguously promote conservation. In the absence of such accompanying regulation, however, policy makers should be careful when stimulating wildlife farming and be aware of potentially adverse consequences.     

Divorce and extrapair mating in female black-capped chickadees (Parus atricapillus): separate strategies with a common target

Patterns of divorce and extrapair mating can provide insights into the targets of female choice in free-living birds. In resident, site-faithful species with continuous partnerships, the better options and the incompatibility hypotheses provide the most likely explanations for divorce. Extrapair mating can be explained by a number of hypotheses often making similar predictions. For example, the good genes and future partnerships hypo- theses predict similar patterns if males with good genes also make the best future partners. By considering both divorce and extrapair mating, it may be possible to distinguish between these comparable hypotheses. We examined natural patterns of divorce and extrapair mating in a long-term study of black-capped chickadees (Parus atricapillus). Out of 144 partnerships over 8 years, we observed 11 divorces and 38 faithful pairs between seasons. Females usually divorced between their first and second breeding seasons for males of higher social rank than their previous partners, had similar reproductive success prior to divorce as females who retained their previous partners, and did not divorce on the basis of previous reproductive success. These results confirm earlier experimental evidence that females divorce for better options. Females who divorced were significantly more likely to have had mixed-paternity broods prior to divorce than females who stayed with their previous partners. There was no evidence that females divorced in favour of previous extrapair partners. These results support the good genes hypothesis for extrapair mating, suggesting that female chickadees use divorce and multiple mating as separate strategies sharing a common target. Received: 4 February 2000 / Revised: 20 July 2000 / Accepted: 4 September 2000     

Singing performance,frequency matching and courtship success of long-tailed manakins (Chiroxiphia linearis)

We examined the relationship between song performance and courtship success in the lek-mating long-tailed manakin (Chiroxiphia linearis) of Costa Rica. Teams of male manakins form cooperative partnerships consisting of a dominant alpha male and a beta male partner with a variable number of subordinate affiliates. Each alpha and beta partnership performs a joint song virtually in unison, which attracts females to their lek arena. We quantified four aspects of song performance, including synchrony, degree of consistency in the alpha male's singing, degree of consistency in the beta male's singing, and degree of sound frequency matching between partners. When all four variables were included in a discriminant function analysis, average frequency matching alone was useful in discriminating between teams with high rates of visitation by females and those with low visitation rates. Only frequency matching was correlated with the rate at which females visited display lek arenas. We propose that the degree of frequency matching provides an unambiguous ideal against which dual-male courtship performance can be assessed. This aspect of song performance may provide information useful to females in assesing a potential mate's ability to form a cooperative long-term partnership.     

How Many Plants Feed the World?

Abstract: FAO food supply data for 146 countries were analyzed to identify the plant commodities that account for the top 90% of each country's per capita supply of food plants by weighs calories, protein, and fat. The plant commodities were divided into two groups: species commodities, such as "cabbages," that can be attributed to particular species; and general commodities, such as "hydrogenated oils," whose species composition is not known. A total of 82 species commodities and 28 general commodities contribute 90% of national per capita supplies of food plants. The 82 species commodities consist of 103 species. Fifty-six of these commodities, comprising 75 species, individually account for 5% or more of at least one county's supply of a nutritional category (plant weight, plant calories, plant protein, plant fag. These figures are several times higher than previous findings that very few (7–30) plant species feed the world. The new figures are considered more accurate because they derive from national supply rather than global production data and from several separate measures of the importance of a food commodity rather than one. The results suggest that (1) plant species diversity remains a significant factor for world food supply; and (2) a conservation priority is to maintain both this wider away of species and the diversity of genetic variants that comprise each species.     

Indirect benefits of symbiotic coccoids for an ant-defended myrmecophytic tree

The net benefits of mutualism depend directly on the costs and effectiveness of mutualistic services and indirectly on the interactions that affect those services. We examined interactions among Cordia alliodora myrmecophytic trees, their symbiotic ants Azteca pittieri, coccoid hemipterans, and foliar herbivores in two Neotropical dry forests. The tree makes two investments in symbiotic ants: it supplies nesting space, as domatia, and it provides phloem to coccoids, which then produce honeydew that is consumed by ants. Although higher densities of coccoids should have higher direct costs for trees, we asked whether higher densities of coccoids can also have higher indirect benefits for trees by increasing the effectiveness of ant defense against foliar herbivores. We found that trees benefited from ant defense against herbivores. Ants defended trees effectively only when colonies reached high densities within trees, and ant and coccoid densities within trees were strongly positively correlated. The benefits of reduced foliar herbivory by larger ant colonies were therefore indirectly controlled by the number of coccoids. Coccoid honeydew supply also affected per capita ant aggression against tree herbivores. Ants experimentally fed a carbohydrate-rich diet, analogous to sugar obtained from coccoids, were more aggressive against caterpillars per capita than ants fed a carbohydrate-poor diet. Ant defense was more effective on more valuable and vulnerable young leaves than on older leaves. Young domatia, associated with young leaves, contained higher coccoid densities than older domatia, which suggests that coccoids may also drive spatially favorable ant defense of the tree. If higher investments by one mutualistic partner are tied to higher benefits received from the other, there may be positive feedback between partners that will stabilize the mutualism. These results suggest that higher investment by trees in coccoids leads to more effective defense by ants against the tree's foliar herbivores.     

Mortality and other determinants of bird divorce rate

Pair bonds can end in two different ways: either death of the partner or divorce, where the frequency of divorce varies enormously among bird species, from 0% to 100%. To better understand this variation, we created and analyzed the largest dataset so far, consisting of 158 species and 20 variables that quantify the species’ body size, life history, diet, and other characteristics. Our results suggest that species with a high divorce rate have a high mortality rate, tend to be ornamented and sexually dichromatic, live colonially, and form part-time rather than continuous partnerships. Traits quantifying body size or life history are often nonlinearly related with divorce rate. These nonlinearities might (partly) be caused by nonlinear relationships of the same traits with mortality rate which is, in turn, linearly related with divorce rate. In contrast to what has been found previously, mortality rate appears as a key factor for divorce rate in our study. This makes sense, as the likelihood that a partner survives from one year to the next decreases with increasing mortality rate, diminishing the likely success of a partner that attempts to locate its previous partner. We also found taxonomic differences in divorce rate. Specifically, Anseriformes have an exceptionally low divorce rate, which, however, can be explained by the generally important determinants of divorce rate: They also have a lower mortality rate, lower degree of ornamentation and coloniality, and more continuous partnerships than members of other orders. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.