•An adaptive, encounter-conditional model of heading change and step-size is proposed.•This method of search outperforms Lévy search if prey are spatially clustered.•Our search model is also a ...Bayesian statistical model that can be fit to data.•One can use encounter-annotated GPS tracks to test the predictions of the model quantitatively.
A theoretical and applied literature has suggested that foragers search using Lévy flights, since Lévy flights can maximize the efficiency of search in the absence of information on the location of randomly distributed prey. Foragers, however, often have available to them at least some information about the distribution of prey, gained either through evolved mechanisms, experience and memory, or social transmission of information. As such, we might expect selection for heuristics that make use of such information to further improve the efficiency of random search. Here we present a general model of random search behavior that includes as special cases: area-restricted search, correlated random walks, Brownian search, and Lévy flights. This generative model allows foragers to adjust search parameters based on encounter-conditional and other heuristics. Using a simulation model, we demonstrate the efficiency gains of these search heuristics, and illustrate the resulting differences in the distributions of step-size and heading angle change they imply, relative to Lévy flights. We conclude by presenting a statistical model that can be fit to empirical data and a set of testable, quantitative predictions that contrast our model of adaptive search with the Lévy flight foraging hypothesis.
We report functional relationships between humans and canines based on observations in the village of Santa Cruz (Toledo District, Belize), emphasizing the cultural ecology of dogs in this lowland ...tropical rainforest setting and milpa agriculture subsistence system. Dogs pursue animals threatening field crops; they deter forest herbivores by leaving their scent along the myriad trails from the village to the milpa field plots; and they guard the homestead and foods stored there. Dogs also aid in daytime hunts for species that can be cornered. They are less useful in pursuits of fast species like deer and are protected from pursuing especially dangerous species like anteater or warri. Litter survival rates are low, and the lifespan of hunting dogs is significantly shorter than that of guard dogs due to hazards of forest pursuit. Explicit training for hunting is limited and maintenance costs are low as dogs are fed a partial ration of tortillas and otherwise scavenge for their diet. The village population of dogs appears not to be under genetic selection for hunting skills. Our results advance the comparative ethnographic study of this important domesticate; they should aid in the formulation and assessment of hypotheses about dog domestication and co-evolution with human society.
Diverse studies of human foraging have revealed behavioral strategies that may have evolved as adaptations for foraging. Here, we used an outdoor experimental search task to explore the effect of ...three sources of information on participants’ performance: (i) information obtained directly from performing a search, (ii) information obtained prior to testing in the form of a distilled snippet of knowledge intended to experimentally simulate information acquired culturally about the environment, and (iii) information obtained from experience of foraging for natural resources for economic gain. We found that (i) immediate searching experience improved performance from the beginning to the end of the short, 2-min task, (ii) information priming improved performance notably from the very beginning of the task, and (iii) natural resource foraging experience improved performance to a lesser extent. Our results highlight the role of culturally transmitted information as well as the presence of mechanisms to rapidly integrate and implement new information into searching choices, which ultimately influence performance in a foraging task.
We develop a method of analysis for testing the marginal value theorem (MVT) in natural settings that does not require an independent definition or mapping of patches. We draw on recent theoretical ...work on area-restricted search (ARS) that links turningangle and step-size changes to geographically localized encounterrates. These models allow us to estimate “giving-up times” using encounter-annotated GPS tracking data. Applied to a case study of Nahua mushroom foragers, these models identify distinct forms of intrapatch and interpatch search behavior, with intrapatch search transitioning to interpatch search after a predictable interval of time since the last encounter with a harvested mushroom. Our empirical estimate of giving-up time coincides with the theoretically optimal giving-up time derived under the MVT in the same environment. The MVT is currently underused in studies of human foraging and settlement patterns, due in large part to the difficulty of identifying discrete resource patches and quantifying their characteristics. Our methods mitigate the need to make such discrete maps of patches and thus have the potential to broaden the scope for empirical evaluations of the MVT and related theory in humans. Beyond studies of naturalistic foraging in humans and other animals, our approach has implications for optimization of search behavior in a range of applied fields where search dynamics must be adapted to shifting patterns of environmental heterogeneity affecting prey density and patchiness.
While it is commonly assumed that farmers have higher, and foragers lower, fertility compared to populations practicing other forms of subsistence, robust supportive evidence is lacking. We tested ...whether subsistence activities-incorporating market integration-are associated with fertility in 10,250 women from 27 small-scale societies and found considerable variation in fertility. This variation did not align with group-level subsistence typologies. Societies labeled as "farmers" did not have higher fertility than others, while "foragers" did not have lower fertility. However, at the individual level, we found strong evidence that fertility was positively associated with farming and moderate evidence of a negative relationship between foraging and fertility. Markers of market integration were strongly negatively correlated with fertility. Despite strong cross-cultural evidence, these relationships were not consistent in all populations, highlighting the importance of the socioecological context, which likely influences the diverse mechanisms driving the relationship between fertility and subsistence.
Monitoring wild edible fungi over long periods is essential to understand how environmental or cultural factors influence fruiting patterns. Since conventional sampling methods are time and resource ...intensive, alternatives providing reliable ecological information could be useful for assessments of fungal management. Traditional ecological knowledge (TEK) can be used as a sampling alternative in a cost-effective manner. Thus, in this paper we aim to: (1) illustrate how GPS-recorded information on mushroom gatherers’ pathways can be used to describe fungal diversity and distribution patterns, and (2) outline a TEK-monitoring proposal that can provide communities and researchers with high-quality ecological data on edible mushrooms. Using information from 32 trips (55 GPS-tracked pathways) we were able to describe the frequency, abundance, diversity and spatial distribution of edible fungi at different sites. We recorded the collection of 6,905 sporocarps, representing 20 species and 6 genera, which were collected or identified at 2,683 locations. In addition to
collections
, we suggest consistent recording of fungal encounters defined as
memory
,
exploration
,
traces
, and
failed collection
, as these also provide ecological information. The most gathered species,
Turbinellus floccosus
and
Clitocybe gibba
, were also among the mushrooms most frequently listed by local people. Finally, we propose combining our GPS-tracking method with a thorough TEK investigation and participatory research in order to develop adaptive co-management strategies that allow local people to manage and conserve their forests through the integration of traditional and scientific knowledge.
Abstract Some of the strongest evidence for sex differences in human cognition relate to spatial abilities, with men traditionally reported to outperform women. Recently, however, such differences ...have been shown to be task dependent. Supporting the argument that a critical factor selecting for sex differences in spatial abilities during human evolution is likely to have been the division of labor during the Pleistocene, evidence is accumulating that women excel on tasks appropriate to gathering immobile plant resources, while men excel on tasks appropriate to hunting mobile, unpredictable prey. Most research, with the exception of some recent experimental field studies, has been conducted in the laboratory, with little information available on how men and women actually forage under natural conditions. In a first study, we GPS-tracked the foraging pathways of 21 pairs of men and women from an indigenous Mexican community searching for mushrooms in a natural environment. Measures of costs, benefits and general search efficiency were analyzed and related to differences between the two sexes in foraging patterns. Although men and women collected similar quantities of mushrooms, men did so at significantly higher cost. They traveled further, to greater altitudes, and had higher mean heart rates and energy expenditure (kcal). They also collected fewer species and visited fewer collection sites. These findings are consistent with arguments in the literature that differences in spatial ability between the sexes are domain dependent, with women performing better and more readily adopting search strategies appropriate to a gathering lifestyle than men.
Human adaptation depends on the integration of slow life history, complex production skills, and extensive sociality. Refining and testing models of the evolution of human life history and cultural ...learning benefit from increasingly accurate measurement of knowledge, skills, and rates of production with age. We pursue this goal by inferring hunters' increases and declines of skill from approximately 23,000 hunting records generated by more than 1800 individuals at 40 locations. The data reveal an average age of peak productivity between 30 and 35 years of age, although high skill is maintained throughout much of adulthood. In addition, there is substantial variation both among individuals and sites. Within study sites, variation among individuals depends more on heterogeneity in rates of decline than in rates of increase. This analysis sharpens questions about the coevolution of human life history and cultural adaptation.
This work describes a novel experimental method which allows the systematic recording of behavior in humans using large scale experimental settings. An efficient way to quantify the costs and ...benefits of different searching strategies is presented, illustrated by an example of searching in a social situation, which involves representing behavior as movement paths using Global Positioning System (GPS) technology. In addition to describing the basic test setup, we discuss two main methodological aspects: First, the preprocessing associated with movement data, typically used to overcome methodological problems arising from the recording method, such as the presence of outliers. And second, using data from a pilot experiment conducted during a university practical class, we illustrate calculations of a wide variety of behavioral descriptors based on the paths and observational data of the searching process. Finally, we discuss the potential this method has for psychological research, in which easily implemented variations of the experimental setup can be used to explore a wide variety of cognitive processes or social interactions.
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