Earl R. Keefe’s research while affiliated with University of Utah and other places

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Publications (6)


Fire's impact on threat detection and risk perception among vervet monkeys: Implications for hominin evolution
  • Article

August 2020

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63 Reads

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7 Citations

Journal of Human Evolution

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Christopher Parker

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Earl Keefe

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Kristen Hawkes

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.


The pyrophilic primate hypothesis
  • Article
  • Full-text available

March 2016

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9,039 Reads

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68 Citations

Evolutionary Anthropology Issues News and Reviews

Christopher H. Parker

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Earl R. Keefe

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[...]

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Kristen Hawkes

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.

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Figure 1: Map shows the distribution of plant communities (Olea europea woodland, Lippia javanica shrubland, and Acacia spp. woodland) in and around Donga troop pre (outlined in black) and postburn (outlined in dark gray) home ranges. The 2012 fire scar is also depicted (dashed red line) to highlight the extent of Lippia and Acacia burned. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Figure 2: Scatterplots showing encounters against the amount of time spent in search for each prey type. Orange dots represent encounters in burned habitats (Acacia and Lippia combined), encounters in unburned habitats (Acacia and Lippia combined) are shown in gray. Lines depict smoothed loess curves (derived from models estimated separately for burned and unburned conditions) for burned (orange) and unburned (gray) data. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Figure 3: Scatterplots showing individual encounters with invertebrates (upper) and leaves (lower) through time (measured as number of days passed since burning occurred). Orange dots represent encounters in burned areas and gray dots represent encounters in unburned settings. Lines show smoothed loess curves (derived from separately estimated models for burned and unburned encounters) for data from burned (orange) and unburned (gray) areas. Dotted green lines represent emergence of regrowth. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Figure 4: Average postencounter prey profitability per prey type in unburned (gray, left plot) and burned (orange, right plot) conditions. Whiskers represent a 95% confidence interval and circles represent outliers. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Prey species nutrient and energetic values

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What's burning got to do with it? Primate foraging opportunities in fire-modified landscapes

October 2015

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383 Reads

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19 Citations

American Journal of Physical Anthropology

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.


Burning the Land: An Ethnographic Study of Off-Site Fire Use by Current and Historically Documented Foragers and Implications for the Interpretation of Past Fire Practices in the Landscape Author(s): Fulco Scherjon, Corrie Bakels, Katharine MacDonald, and Wil Roebroeks Source: Current Anthropology, Vol. 56, No. 3 (June 2015), pp. 299-326 Published by: The University of Chicago Press on behalf of Wenner-Gren Foundation for Anthropological Research

June 2015

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848 Reads

Current Anthropology


Burning the Land: An Ethnographic Study of Off-Site Fire Use by Current and Historically Documented Foragers and Implications for the Interpretation of Past Fire Practices in the Landscape Author(s): Fulco Scherjon, Corrie Bakels, Katharine MacDonald, and Wil Roebroeks Source: Current Anthropology, Vol. 56, No. 3 (June 2015), pp. 299-326 Published by: The University of Chicago Press on behalf of Wenner-Gren Foundation for Anthropological Research

June 2015

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143 Reads

Current Anthropology


Fire and Home Range Expansion: A Behavioral Response to Burning Among Savanna Dwelling Vervet Monkeys (Chlorocebus aethiops)

August 2014

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354 Reads

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34 Citations

American Journal of Physical Anthropology

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.

Citations (4)


... While the interpretations we can make for vervet monkeys are more limited due to the low number of detections across our study, the relative abundance patterns observed leave open the possibility that vervet monkeys (~4 kg) may also have been able to largely evade the Cyclone Idai floodwaters through behavioral adjustments. In common with baboons, vervet monkeys are known to be highly adaptable as a species, surviving in harsh conditions and responding flexibly to change (Herzog et al. 2016(Herzog et al. , 2020Jaffe and Isbell 2009;McDougall et al. 2010;Pasternak et al. 2013;Wrangham 1981), such as adjusting their activity to spend more time resting at the expense of feeding to cope in extreme heat (McFarland et al. 2014) and exhibiting foraging flexibility in response to available food resources and the frequency of human interactions in urban environments (Thatcher, Downs, and Koyama 2020). Aside from our own species, baboons and vervet monkeys are the most widely distributed of the African primates, occupying a diverse range of habitats across the African continent (Wolfheim 1983). ...

Reference:

Effects of an Extreme Weather Event on Primate Populations
Fire's impact on threat detection and risk perception among vervet monkeys: Implications for hominin evolution
  • Citing Article
  • August 2020

Journal of Human Evolution

... Both archaeological and ethnographic accounts indicate that fire was often used in the past to clear vegetation, creating patchy mosaic landscapes to promote biodiversity, manage resources, and enhance habitat diversity (Bird, 1995;Thompson et al., 2021). Given the timeframe and context of the archaeological occupations from the KLP, the uses of fire in this context would have been for warmth, cooking, socialization, and potentially landscape clearance of riparian areas to improve visibility for hunting or improved foraging opportunities for seasonally available plants (Glikson, 2013;Parker et al., 2016). On balance, we argue that the fire ecology of this region favors anthropogenic ignition sources over natural ignition sources. ...

The pyrophilic primate hypothesis

Evolutionary Anthropology Issues News and Reviews

... While the interpretations we can make for vervet monkeys are more limited due to the low number of detections across our study, the relative abundance patterns observed leave open the possibility that vervet monkeys (~4 kg) may also have been able to largely evade the Cyclone Idai floodwaters through behavioral adjustments. In common with baboons, vervet monkeys are known to be highly adaptable as a species, surviving in harsh conditions and responding flexibly to change (Herzog et al. 2016(Herzog et al. , 2020Jaffe and Isbell 2009;McDougall et al. 2010;Pasternak et al. 2013;Wrangham 1981), such as adjusting their activity to spend more time resting at the expense of feeding to cope in extreme heat (McFarland et al. 2014) and exhibiting foraging flexibility in response to available food resources and the frequency of human interactions in urban environments (Thatcher, Downs, and Koyama 2020). Aside from our own species, baboons and vervet monkeys are the most widely distributed of the African primates, occupying a diverse range of habitats across the African continent (Wolfheim 1983). ...

What's burning got to do with it? Primate foraging opportunities in fire-modified landscapes

American Journal of Physical Anthropology

... Past research into the effects of fire on home ranges shows considerable variation between mammal species. Some species show no change in home range size following wildfire [22,82,134,138], while others expand their home ranges following fire [50,54] or reduce them [105]. Increases in home range sizes have been attributed to easier movement through landscapes to find resources in the absence of understorey vegetation [54] or the need to move farther to find food if its availability is reduced [82,133]. ...

Fire and Home Range Expansion: A Behavioral Response to Burning Among Savanna Dwelling Vervet Monkeys (Chlorocebus aethiops)

American Journal of Physical Anthropology