Gazing at Social Interactions Between Foraging and Decision Theory

Finding the underlying principles of social attention in humans seems to be essential for the design of the interaction between natural and artificial agents. Here, we focus on the computational modeling of gaze dynamics as exhibited by humans when perceiving socially relevant multimodal information. The audio-visual landscape of social interactions is distilled into a number of multimodal patches that convey different social value, and we work under the general frame of foraging as a tradeoff between local patch exploitation and landscape exploration. We show that the spatio-temporal dynamics of gaze shifts can be parsimoniously described by Langevin-type stochastic differential equations triggering a decision equation over time. In particular, value-based patch choice and handling is reduced to a simple multi-alternative perceptual decision making that relies on a race-to-threshold between independent continuous-time perceptual evidence integrators, each integrator being associated with a patch.

On the use of private versus social information in oviposition site choice decisions by Drosophila melanogaster females

Individuals are faced with decisions throughout their lifetimes, and the choices they make often have important consequences toward their fitness. Being able to discern which available option is best to pursue often incurs sampling costs, which may be largely avoided by copying the behavior and decisions of others. Although social learning and copying behaviors are widespread, much remains unknown about how effective and adaptive copying behavior is, as well as the factors that underlie its expression. Recently, it has been suggested that since female fruit flies (Drosophila melanogaster) appear to rely heavily on public information when selecting oviposition sites, they are a promising model system for researching patch-choice copying, and more generally, the mechanisms that control decision making. Here, we set out to determine how well female distinguish between socially produced cues, and whether females are using “relevant” signals when choosing an oviposition site. We found that females showed a strong preference for ovipositing on media patches that had been previously occupied by ovipositing females of the same species and diet over other female outgroups. However, in a separate assay, we observed that females favored ovipositing on media patches that previously housed virgin males over those exhibiting alternative conspecific signals. Our results confirm that females use cues left behind by other flies when choosing between potential oviposition sites, though their prioritization of these signals raises serious questions as to whether fruit flies are employing copying behavior, or are instead responding to signals that may not be of relevance to oviposition site suitability.

Supplementing Maize Agriculture in Basketmaker II Subsistence: Dietary Analysis of Human Paleofeces from Turkey Pen Ruin (42SA3714)

This research explores the factors that motivated increasing reliance on maize during the Basketmaker II period in the North American Southwest. Through the analysis of 44 human paleofeces from Turkey Pen Ruin, Utah, I investigate resource choice and nutritional supplementation of maize before the advent of bean horticulture. In order to discern what resources provided caloric and nutritional supplementation to maize, all paleofecal specimens were analyzed for pollen and macrofossil content, and 20 were further sampled for PCR analysis targeted at several select animal and plant species. Eight paleofecal specimens from various stratigraphic layers were directly AMS dated in order to better assess the chronology of the midden from which they were excavated, and to determine their cultural phase association. The resulting data allowed for the testing of three hypotheses based in human behavioral ecology, specifically applying diet-breadth and patch-choice models. The results of this project demonstrate that the diet of these early maize farmers was relatively broad, and included a high proportion of resources with lower caloric returns than maize. Furthermore, plants associated with field and disturbance settings, such as goosefoot (<em>Chenopodium spp</em>.) and purslane (<em>Portulaca spp</em>.), which provide excellent nutritional complements to maize, made large contributions to the diet. Overall, these findings indicate that people were pushed to increase their reliance on farming due to resource depression, and that the anthropogenic niche created by farming activities encouraged greater focus on the field as a patch of multiple types of resources, and not only as a location for growing maize. The discovery of corn smut (<em>Ustilago maydis</em>) spores in all but one of the specimens studied suggest that this parasitic fungus may also have made a noteworthy contribution to the diet, further supporting the emphasis on the field as a patch. In combination, these data and theoretical analyses help to explain the subsistence choices made by Basketmaker II people. In particular, these results clarify what motivated people to increasingly focus on farming, and highlight the wild resources used to augment maize-based nutrition prior to the incorporation of beans, which provided essential nutrients during later periods.

An energetics-based honeybee nectar-foraging model used to assess the potential for landscape-level pesticide exposure dilution

Estimating the exposure of honeybees to pesticides on a landscape scale requires models of their spatial foraging behaviour. For this purpose, we developed a mechanistic, energetics-based model for a single day of nectar foraging in complex landscape mosaics. Net energetic efficiency determined resource patch choice. In one version of the model a single optimal patch was selected each hour. In another version, recruitment of foragers was simulated and several patches could be exploited simultaneously. Resource availability changed during the day due to depletion and/or intrinsic properties of the resource (anthesis). The model accounted for the impact of patch distance and size, resource depletion and replenishment, competition with other nectar foragers, and seasonal and diurnal patterns in availability of nectar-providing crops and wild flowers. From the model we derived simple rules for resource patch selection, e.g., for landscapes with mass-flowering crops only, net energetic efficiency would be proportional to the ratio of the energetic content of the nectar divided by distance to the hive. We also determined maximum distances at which resources like oilseed rape and clover were still energetically attractive. We used the model to assess the potential for pesticide exposure dilution in landscapes of different composition and complexity. Dilution means a lower concentration in nectar arriving at the hive compared to the concentration in nectar at a treated field and can result from foraging effort being diverted away from treated fields. Applying the model for all possible hive locations over a large area, distributions of dilution factors were obtained that were characterised by their 90-percentile value. For an area for which detailed spatial data on crops and off-field semi-natural habitats were available, we tested three landscape management scenarios that were expected to lead to exposure dilution: providing alternative resources than the target crop (oilseed rape) in the form of (i) other untreated crop fields, (ii) flower strips of different widths at field edges (off-crop in-field resources), and (iii) resources on off-field (semi-natural) habitats. For both model versions, significant dilution occurred only when alternative resource patches were equal or more attractive than oilseed rape, nearby and numerous and only in case of flower strips and off-field habitats. On an area-base, flower strips were more than one order of magnitude more effective than off-field habitats, the main reason being that flower strips had an optimal location. The two model versions differed in the predicted number of resource patches exploited over the day, but mainly in landscapes with numerous small resource patches. In landscapes consisting of few large resource patches (crop fields) both versions predicted the use of a small number of patches.

Public information use by foraging ninespine sticklebacks: Social learning or an unlearned social influence on travel direction?

If we are to understand the cognitive basis and evolutionary origins of a particular behaviour, it is necessary to identify its underlying mechanism. Ninespine sticklebacks (Pungitius pungitius) can identify the richer of two prey patches by observing other foragers’ success. This may be due to social learning, or an unlearned social effect on travel direction, brought about by the fish being more likely to face and subsequently travel towards areas where they have observed more feeding activity. Here we show that observer orientation does not predict patch choice, and that fish are still more likely to spend more time in richer patches even if they have to take an indirect route to reach them. This suggests that sticklebacks can learn the location of the richer patch through observation, and viewed in conjunction with other published findings, suggests that learned local enhancement lies behind public information use in this species.