Although extrafloral nectar (EFN) is a key food resource for arboreal ants, its role in structuring ground-nesting ant communities has received little attention, despite these ants also being frequent EFN-attendants. We investigated the role of EFN as a driver of the spatial structure of ground-nesting ant communities occurring in dry forest in north-eastern Brazil. We examined the effects on this relationship of two global drivers of biodiversity decline, chronic anthropogenic disturbance and climate change (through decreasing rainfall). We mapped EFN-producing plants and ant nests in 20 plots distributed along independent gradients of disturbance and rainfall. We categorized ant species into three types according to their dependence on EFN: heavy users, occasional users and non-users. We found a strong relationship between ant dependence on EFN and nest proximity to EFN-producing plants: heavy-users (mean distance 1.1 m) nested closer to EFN-producing plants than did occasional users (1.7 m), which in turn nested closer to EFN-producing plants than did non-users (2.3 m). Neither disturbance nor rainfall affected the proximity of heavy-user nests to EFN-producing plants. Our study shows for the first time that EFN is a key driver of the spatial structure of entire communities of ground-nesting ants.

A generalist predator's ability to contribute to biological control is influenced by the decisions it makes during foraging. Predators often use flexible foraging tactics, which allows them to pursue specific types of prey at the cost of reducing the likelihood of capturing other types of prey. When a pest insect has low nutritional quality or palatability for a predator, the predator is likely to reject that prey in favour of pursuing alternative, non-pest prey. This is often thought to limit the effectiveness of generalist predators in consuming aphids, which are of low nutritional quality for many generalist predators. Here, we report behavioural assays that test the hypothesis that the generalist predator, Grammonota inornata (Araneae: Linyphiidae), preferentially forages for a non-pest prey with high nutritional quality (springtails), and rejects a pest prey with low nutritional quality (aphids). In no-choice assays, molecular gut-content analysis revealed that spiders continued to feed on the low-quality aphids at high rates, even when high-quality springtails were readily available. When provided a choice between aphids and springtails in two-way choice tests, spiders did not show the expected preference for springtails. Decision-making by spiders during foraging therefore appears to be sub-optimal, possibly because of attraction to the less frequently encountered of two preys as part of a dietary diversification strategy. These results indicate that behavioural preferences alone do not necessarily compromise the pest-suppression capacity of natural enemies: even nutritionally sub-optimal pest prey can potentially be subject to predation and suppression by natural enemies.

Research has shown that consumers of wildlife are price sensitive and that the quantity of meat purchased is influenced by the cost of bushmeat and its substitutes. Although there is evidence that hunter-gatherers are optimal foragers whose behaviour is influenced by costs associated with foraging, there is a paucity of studies on whether the behaviour of bushmeat hunters, like that of consumers, is cost sensitive. This paper reports data on the practices of indigenous bushmeat hunters in the lowland forests of Ecuador before and after a national tax on firearms and ammunition was increased by 300%. Results show that hunters' behaviour is, as predicted by optimal foraging theory, responsive to price signals. After a substantial increase in the national tax on shotgun cartridges, hunters modified the set of species considered worth hunting, dropping smaller-bodied species from the set of species they target during a hunt and switching the technology used for hunting, increasingly using muzzle loader shotguns and thus avoiding the cost of expensive cartridges.

Although seed-size preference by granivores is relative to the sizes of seeds offered by researchers, preferences are often inappropriately discussed and interpreted as if they are for absolute seed sizes. Granivores often prefer relatively small seeds in forests and relatively large seeds in herbaceous communities, although the absolute size of preferred seeds in each is often similar. These results are consistent with predictions of optimal foraging theory. Researchers are encouraged to take heed of optimal foraging theory and both relative and absolute seed size when interpreting seed-size preferences.

Managers in southern Africa are concerned that continually increasing elephant populations will degrade ecosystems. Culling, translocation and birth control are flawed solutions. An alternative is providing elephants more space but this hinges on identifying landscape preferences. We examined two diverse ecosystems and uncovered similarities in elephant habitat use, expressing these as ‘rules’. We considered arid Etosha National Park, (Namibia) and the tropical woodlands of Tembe Elephant Park (South Africa) and Maputo Elephant Reserve (Mozambique). Landscape data consisted of vegetation types, distances from water and settlements. To surmount issues of scale and availability we incorporated elephant movements as a function that declined as distance from an elephant's location increased. This presumes that elephants optimize trade-offs between benefiting from high-quality resources and costs to find them. Under a likelihood-based approach we determined the important variables and shapes of their relationships to evaluate and compare models separated by gender, season and location. After considering elephants' preferences for areas nearby, habitat use usually increased with proximity to water in all locations. Elephants sought places with high proportions of vegetation, especially when neighbouring areas had low vegetative cover. Lastly, elephants avoided human settlements (when present), and cows more so than bulls. In caricature, elephants preferred to move little, drink easily, eat well, and avoid people. If one makes more areas available, elephants will probably favour areas near water with high vegetative cover (of many different types) and away from people. Managers can oblige elephants’ preferences by supplying them. If so, they should anticipate higher impacts to neighbouring vegetation.

The distribution and formation of foraging trails have largely been neglected as factors explaining harvesting patterns of leaf-cutting ants. We applied fractal analysis, circular, and conventional statistics to published and newly recorded trail maps of seven Atta colonies focusing on three aspects: permanence, spatio-temporal plasticity and colony life stage. In the long term, trail patterns of young and mature Atta colonies revealed that foraging activities were focused on distinct, static sectors that made up only parts of their potentially available foraging range. Within these foraging sectors, trails were typically ephemeral and highly variable in space and time. These ephemeral trails were concentrated around permanent trunk trails in mature and around nest entrances in young colonies. Besides these similarities, the comparison of trail systems between the two life stages indicated that young colonies exploited fewer leaf sources, used smaller and less-complex systems of foraging trails, preferred different life forms as host plants, and switched hosts more often compared with mature colonies. Based on these analyses, we propose a general hypothesis which describes the foraging pattern in Atta as a result of initial foraging experiences, spatio-temporal distribution of suitable host plants, energetic constraints, and other factors such as seasonality and interspecific predation.

Lions Panthera leo are generally thought to prey on medium to large ungulates. Knowledge of which species are actually preferred and which are avoided is lacking, however, as is an understanding of why such preference or avoidance may arise. An analysis of 32 studies over 48 different spatial locations or temporal periods throughout the distribution of the lion shows that it preferentially preys upon species within a weight range of 190–550 kg. The most preferred weight of lion prey is 350 kg. The mean mass of significantly preferred prey species is 290 kg and of all preferred species is 201 kg. Gemsbok, buffalo, wildebeest, giraffe and zebra are significantly preferred. Species outside the preferred weight range are generally avoided. Species within the preferred weight range that are not significantly preferred (such as roan, sable and eland) generally have features that reduce predation either morphologically (e.g. sable horns), ecologically (e.g. roan and sable occurring at low density), or behaviourally (e.g. the large herd size and increased vigilance of eland). Warthog are below the preferred weight range yet are taken in accordance with their availability and this is probably due to their sympatry with lion, their relatively slow evasion speed and their lower level of vigilance. Plots of prey preference against prey body mass follows a bell curve with a right skew that, we argue, is caused by collective hunting by lions of larger-bodied prey. Our methods can be used on all large predators and are likely to be useful in assessing competition in sympatric communities of predators, cooperative hunting and predicting predator diets. This will allow us to move beyond descriptive dietary studies to improve our predictive understanding of the mechanisms underlying predator–prey interactions.