Christopher H. Parker’s research while affiliated with University of Utah and other places

The spatial behavior of primates is shaped by many factors including predation risk, the distribution of food sources, and access to water. In fire-prone settings, burning is a catalyst of change, altering the distribution of both plants and animals. Recent research has shown that primates alter their behavior in response to this change. Here, we study primates' perceived threat of predation in fire-modified landscapes. We focus on the predator-related behaviors of vervet monkeys (Chlorocebus pygerythrus) after controlled burning events. We compare the occurrence of vigilance and predator-deterrent behaviors, including alarm calls, scanning, and flight across different habitats and burn conditions to test the hypothesis that subjects exhibit fewer predator-specific vigilance and predator-deterrent behaviors in burned areas. The results demonstrate that predator-related behaviors occur less often in burned habitats, suggesting that predators are less common in these areas. These results provide foundations for examining hypotheses about the use of fire-altered landscapes among extinct hominins. We set these data in the context of increasing aridity, changes in burning regimes, and the emergence of pyrophilia in the human lineage.

Optimal foraging theory is a set of concepts and models that aim to explain the wide variation in foraging strategies among individuals and between species, guided by the assumption that living things are designed by a history of natural selection. The use of foraging models in anthropology was prompted by the geographic and temporal variation in resource use among people who live on wild foods. Foraging models provide a theoretical basis for linking the variation both among and within populations to features of local ecology—with initially unexpected implications for what has happened in human evolution.

Explanations for the complex human decisions that lead to territoriality have focused on models of economic defendability. While powerful, these models fail to explain variation in territorial behavior in all cases. To help overcome this limitation, here we offer an approach that synthesizes the logic of economic defendability with a general optimality model from behavioral ecology: the marginal value theorem (MVT). Through the MVT we add considerations of how resource profitability, in addition to abundance, alters the amount of time individuals should spend foraging in order to meet caloric requirements, and how far they should travel between foraging locations. Where and when individuals rely on abundant, but lower profitability resources, they should spend more time foraging and less time traveling, which leads to smaller territories that are easier to defend, and wherein each unit of land has a greater economic value per capita thereby increasing the benefits of economic boundary defense. Numic foragers of the Great Basin and surrounding areas provide an illustrative case study to validate this general ecological model. The results show that individuals exploiting high density but low profitability resources live in smaller territories and have higher rates of resource privatization, thereby explaining societal differences between Northern Paiute and Shoshone bands. Importantly, because defended resource patches are the target of women's foraging, the payoffs to territoriality are likely structured by women's risk averse foraging decisions. We suggest this model is capable of explaining variation in hunter-gatherer territoriality worldwide.

We utilized the Dyson-Hudson and Smith model of economic defensibility, combined with the Charnov patch choice in an effort to help explain the threshold for territorial behavior within foraging populations. We found that as foraging becomes more intensive and populations become more dense, there is a greater likelihood of both ownership of goods and defensive behavior.

Archaeological investigations of hunter-gatherer site structure have remained largely descriptive, despite significant explanatory advancements by evolutionary approaches to foraging behavior and ecology. To date, calls to incorporate site structure studies within this behavioral ecological framework have largely been ignored. We suggest there is a clear explanation for this. At large spatial extents, human behavior is constrained by patterned ecological variability, as such, a general theory of behavior is likely to characterize key aspects of human decisions. At small spatial extents, human behavior is not constrained by patterned ecological variability, therefore, the human decisions that produce site structure should be driven by mechanical constraints or random variation. However, variation in site structure may be ecologically relevant inasmuch as it informs on landscape level variation in human-environment interactions. Drawing on ethnoarchaeological data collected in collaboration with Martu, Aboriginal foragers in Western Australia, here we test empirically-derived, mechanistic predictions on site size and material size sorting to show how these can inform theoretically-derived, adaptive predictions from the Marginal Value Theorem. Results show that site size increases with the number of occupants and hence, the amount of in-patch foraging competition, while size sorting increases with the duration of occupation and hence, in-patch residence time. Combined, these attributes of site structure can be used as proxies of foraging behavior to explain variability in overall foraging yields. With this approach, site structure can provide insights into foraging decisions that can be examined through a general theory of behavior.

Members of genus Homo are the only animals known to create and control fire. The adaptive significance of this unique behavior is broadly recognized, but the steps by which our ancestors evolved pyrotechnic abilities remain unknown. Many hypotheses attempting to answer this question attribute hominin fire to serendipitous, even accidental, discovery. Using recent paleoenvironmental reconstructions, we present an alternative scenario in which, 2 to 3 million years ago in tropical Africa, human fire dependence was the result of adapting to progressively fire-prone environments. The extreme and rapid fluctuations between closed canopy forests, woodland, and grasslands that occurred in tropical Africa during that time, in conjunction with reductions in atmospheric carbon dioxide levels, changed the fire regime of the region, increasing the occurrence of natural fires. We use models from optimal foraging theory to hypothesize benefits that this fire-altered landscape provided to ancestral hominins and link these benefits to steps that transformed our ancestors into a genus of active pyrophiles whose dependence on fire for survival contributed to its rapid expansion out of Africa.

Objectives: Anecdotal and formal evidence indicate that primates take advantage of burned landscapes. However, little work has been done to quantify the costs and benefits of this behavior. Using systematic behavioral observations from a population of South African vervet monkeys (Chlorocebus aethiops pygerythrus), we evaluate differences in food availability and energetics before and after controlled burns altered vegetation near their home range. We aim to determine whether burned habitats offer improved foraging opportunities. Methods: We collected feeding data from foraging individuals and analyzed common plant foods for their energetic content. We then used the feeding and energetic data to calculate postencounter profitabilities and encounter rates for food types. Using negative binomial and mixed linear regression models we compared data from burned and unburned habitats. Results: Our results show significantly improved encounter rates in burned landscapes for two prey items, invertebrates and grasses. However, postencounter profitabilities in burned areas were not significantly different than those achieved in unburned areas. Conclusions: Results suggest that improved encounters alone can motivate changes in foraging behavior. These foraging benefits enable the exploitation of burned savanna habitats, likely driving postburn range expansions observed among populations of vervet monkeys. Thus quantified, these results may serve as a foundation for hypotheses regarding the evolution of fire-use in our own lineage. Am J Phys Anthropol, 2015. © 2015 Wiley Periodicals, Inc.

The behavioral adaptations of primates to fire-modified landscapes are of considerable interest to anthropologists because fire is fundamental to life in the African savanna-the setting in which genus Homo evolved. Here we report the behavioral responses of a savanna-dwelling primate, vervet monkeys (Chlorocebus aethiops), to fire-induced ecological change. Using behavioral and spatial data to characterize ranging patterns prior to and postburn and between burn and nonburn years, we show that these primates inhabiting small, spatially bound, riverine habitats take advantage of newly burned savanna landscapes. When subjects encountered controlled fires, they did not flee but instead avoided the path of the fire seemingly unbothered by its approach. After fire, the primates' home range expanded into newly burned but previously unused areas. These results contribute to understanding the response of non-human primates to fire-modified landscapes and can shed light on the nature and scope of opportunities and constraints posed by the emergence of fire-affected landscapes in the past. Results also expose deficiencies in our knowledge of fire-related behavioral responses in the primate lineage and highlight the need for further investigation of these responses as they relate to foraging opportunities, migration, resource use, and especially fire-centric adaptations in our own genus. Am J Phys Anthropol, 2014. © 2014 Wiley Periodicals, Inc.