Distribution and Use of Income from Bushmeat in a Rural Village,Central Gabon

Abstract: Bushmeat hunting is an activity integral to rural forest communities that provides a high proportion of household incomes and protein requirements. An improved understanding of the relationship between bushmeat hunting and household wealth is vital to assess the potential effects of future policy interventions to regulate an increasingly unsustainable bushmeat trade. We investigated the relationship between hunting offtake and household wealth, gender differences in spending patterns, and the use of hunting incomes in two rural forest communities, Central Gabon, from 2003 to 2005. Households in which members hunted (hunting households) were significantly wealthier than households in which no one hunted (nonhunting households), but within hunting households offtakes were not correlated with household wealth. This suggests there are access barriers to becoming a hunter and that hunting offtakes may not be the main driver of wealth accumulation. Over half of the money spent by men in the village shop was on alcohol and cigarettes, and the amount and proportion of income spent on these items increased substantially with increases in individual hunting offtake. By contrast, the majority of purchases made by women were of food, but their food purchases decreased actually and proportionally with increased household hunting offtake. This suggests that the availability of bushmeat as a food source decreases spending on food, whereas hunting income may be spent in part on items that do not contribute significantly to household food security. Conservation interventions that aim to reduce the commercial bushmeat trade need to account for likely shifts in individual spending that may ensue and the secondary effects on household economies.     

Consequences of Buffelgrass Pasture Development for Primary Productivity,Perennial Plant Richness,and Vegetation Structure in the Drylands of Sonora,Mexico

Abstract: In large parts of northern Mexico native plant communities are being converted to non‐native buffelgrass (Pennisetum ciliare) pastures, and this conversion could fundamentally alter primary productivity and species richness. In Sonora, Mexico land conversion is occurring at a regional scale along a rainfall‐driven gradient of primary productivity, across which native plant communities transition from desert scrub to thorn scrub. We used a paired sampling design to compare a satellite‐derived index of primary productivity, richness of perennial plant species, and canopy‐height profiles of native plant communities with buffelgrass pastures. We sampled species richness across a gradient of primary productivity in desert scrub and thorn scrub vegetation to examine the influence of site productivity on the outcomes of land conversion. We also examined the influence of pasture age on species richness of perennial plants. Index values of primary productivity were lower in buffelgrass pastures than in native vegetation, which suggests a reduction in primary productivity. Land conversion reduced species richness by approximately 50% at local and regional scales, reduced tree and shrub cover by 78%, and reduced canopy height. Land conversion disproportionately reduced shrub species richness, which reflects the common practice among Sonoran ranchers of conserving certain tree and cactus species. Site productivity did not affect the outcomes of land conversion. The age of a buffelgrass pasture was unrelated to species richness within the pasture, which suggests that passive recovery of species richness to preconversion levels is unlikely. Our findings demonstrate that land conversion can result in large losses of plant species richness at local and regional scales and in substantial changes to primary productivity and vegetation structure, which casts doubt on the feasibility of restoring native plant communities without active intervention on the part of land managers.     

Thresholds of species loss in Amazonian deforestation frontier landscapes

In the Brazilian Amazon, private land accounts for the majority of remaining native vegetation. Understanding how land‐use change affects the composition and distribution of biodiversity in farmlands is critical for improving conservation strategies in the face of rapid agricultural expansion. Working across an area exceeding 3 million ha in the southwestern state of Rondônia, we assessed how the extent and configuration of remnant forest in replicate 10,000‐ha landscapes has affected the occurrence of a suite of Amazonian mammals and birds. In each of 31 landscapes, we used field sampling and semistructured interviews with landowners to determine the presence of 28 large and medium sized mammals and birds, as well as a further 7 understory birds. We then combined results of field surveys and interviews with a probabilistic model of deforestation. We found strong evidence for a threshold response of sampled biodiversity to landscape level forest cover; landscapes with <30–40% forest cover hosted markedly fewer species. Results from field surveys and interviews yielded similar thresholds. These results imply that in partially deforested landscapes many species are susceptible to extirpation following relatively small additional reductions in forest area. In the model of deforestation by 2030 the number of 10,000‐ha landscapes under a conservative threshold of 43% forest cover almost doubled, such that only 22% of landscapes would likely to be able to sustain at least 75% of the 35 focal species we sampled. Brazilian law requires rural property owners in the Amazon to retain 80% forest cover, although this is rarely achieved. Prioritizing efforts to ensure that entire landscapes, rather than individual farms, retain at least 50% forest cover may help safeguard native biodiversity in private forest reserves in the Amazon. Umbrales de Pérdida de Especies en los Paisajes Fronterizos de Deforestación en el Amazonas Ochoa‐Quintero     

Use of Stress‐Hormone Levels and Habitat Selection to Assess Functional Connectivity of a Landscape for an Amphibian

Abstract: The influence of landscape matrix on functional connectivity has been clearly established. Now methods to assess the effects of different land uses on species’ movements are needed because current methods are often biased. The use of physiological parameters as indicators of the level of resistance to animal movement associated with different land uses (i.e., matrix resistance) could provide estimates of energetic costs and risks to animals migrating through the matrix. To assess whether corticosterone levels indicate matrix resistance, we conducted experiments on substrate choice and measured levels of corticosterone before and after exposure of toads (Bufo bufo) to 3 common substrates (ploughed soil, meadow, and forest litter). We expected matrix resistance and hormone levels to increase from forest litter (habitat of the toad) to meadows to ploughed soil. Adult toads had higher corticosterone levels on ploughed soil than on forest litter or meadow substrates. Hormone levels did not differ between forest litter and meadow. Toads avoided moving onto ploughed soil. Corticosterone levels in juvenile toads were not related to substrate type; however, hormone levels decreased as humidity increased. Juveniles, unlike adults, did not avoid moving over ploughed soil. The difference in responses between adult and juvenile toads may have been due to differences in experimental design (for juveniles, entire body used to measure corticosterone concentration; for adults, saliva alone); differences in the scale of sensory perception of the substrate (juveniles are much smaller than adults); or differences in cognitive processes between adult and juvenile toads. Adults probably had experience with different substrate types, whereas juveniles first emerging from the water probably did not. As a consequence, arable lands could act as ecological traps for juvenile toads.     

Cooperatively breeding carrion crows adjust offspring sex ratio according to group composition

In cooperatively breeding species, parents should bias offspring sex ratio towards the philopatric sex to obtain new helpers (helper repayment hypothesis). However, philopatric offspring might increase within-group competition for resources (local resource competition hypothesis), diluting the benefits of helper acquisition. Furthermore, benefits of offspring sex bias on parents’ fitness may depend on different costs of production and/or different breeding opportunities of sons and daughters. Because of these counteracting factors, strategies of offspring sex allocation in cooperative species are often difficult to investigate. In carrion crows Corvus corone corone in northern Spain, sons are more philopatric and more helpful at the nest than daughters, which disperse earlier and have higher chances to find a breeding vacancy. Consistent with the helper repayment hypothesis, we found that crows fledged more sons in groups short of subordinate males than in groups with sufficient helper contingent, where daughters were preferred. Crow females also proved able to bias primary sex ratio, allocating offspring sex along the hatching sequence in a way that provided the highest fledging probability to sons in the first breeding attempt and to daughters in the following ones. The higher cost of producing male offspring may explain this pattern, with breeding females shifting to the cheapest sex (female) as a response to the costs generated by previous reproductive attempts. Our results suggest complex adjustments of offspring sex ratio that allowed crows to maximize the value of daughters and sons.