Evidence of Lévy walk foraging patterns in human hunter–gatherers

Raichlen, David A.; Wood, Brian M.; Gordon, Adam D.; Mabulla, Audax; Marlowe, Frank W.; Pontzer, Herman

doi:10.1073/pnas.1318616111

Cited by 262 publications

(282 citation statements)

References 39 publications

(52 reference statements)

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“…When limited to random searching, the chance for a successful predator-prey encounter depends largely on the search strategy used (33). In this situation, many motile predators, ranging from microbes to humans, use Lévy flight, a superdiffusive search strategy, to increase their success (28,34,35). To the best of our knowledge, no organism has been shown to use a subdiffusive search strategy to the same effect.…”

Section: Discussionmentioning

confidence: 99%

Subdiffusive motion of bacteriophage in mucosal surfaces increases the frequency of bacterial encounters

Barr

Auro

Sam-Soon

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

168

186

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Bacteriophages (phages) defend mucosal surfaces against bacterial infections. However, their complex interactions with their bacterial hosts and with the mucus-covered epithelium remain mostly unexplored. Our previous work demonstrated that T4 phage with Hoc proteins exposed on their capsid adhered to mucin glycoproteins and protected mucus-producing tissue culture cells in vitro. On this basis, we proposed our bacteriophage adherence to mucus (BAM) model of immunity. Here, to test this model, we developed a microfluidic device (chip) that emulates a mucosal surface experiencing constant fluid flow and mucin secretion dynamics. Using mucus-producing human cells and Escherichia coli in the chip, we observed similar accumulation and persistence of mucus-adherent T4 phage and nonadherent T4Δhoc phage in the mucus. Nevertheless, T4 phage reduced bacterial colonization of the epithelium >4,000-fold compared with T4Δhoc phage. This suggests that phage adherence to mucus increases encounters with bacterial hosts by some other mechanism. Phages are traditionally thought to be completely dependent on normal diffusion, driven by random Brownian motion, for host contact. We demonstrated that T4 phage particles displayed subdiffusive motion in mucus, whereas T4Δhoc particles displayed normal diffusion. Experiments and modeling indicate that subdiffusive motion increases phage-host encounters when bacterial concentration is low. By concentrating phages in an optimal mucus zone, subdiffusion increases their host encounters and antimicrobial action. Our revised BAM model proposes that the fundamental mechanism of mucosal immunity is subdiffusion resulting from adherence to mucus. These findings suggest intriguing possibilities for engineering phages to manipulate and personalize the mucosal microbiome.BAM | virus | mucus | subdiffusion | search strategy I n all animals, mucosal surfaces provide critical immunological services by both protecting against invading bacterial pathogens and supporting large communities of commensal microorganisms (1, 2). Being exposed to the environment, mucosal surfaces are also the infection sites for many important bacterial diseases, including acute diarrhea and cystic fibrosis in humans. This, combined with their accessibility, make mucosal surfaces attractive venues for phage therapy; that is, the use of bacteriophages (phages) to treat and clear bacterial infections (3,4). Clinical success so far has been erratic (5). The complexities and dynamics of the mucus layer are rarely considered, and the activity of phages therein is mostly unknown. Not surprisingly, phages effective in vitro do not consistently reduce mucosal bacterial host levels in vivo (6, 7). An understanding of the interactions between phages and their bacterial hosts within the relevant physiological environment is critical for consistent success of phage therapy applications.The multilayered mucus is composed primarily of gel-forming mucin glycoproteins that are continually secreted by the underlying epithelium (8). The mucin...

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Section: Discussionmentioning

confidence: 99%

Subdiffusive motion of bacteriophage in mucosal surfaces increases the frequency of bacterial encounters

Barr

Auro

Sam-Soon

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

168

186

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“…While there is empirical literature suggesting directionality to prey and/or predator movements (summary in Scharf et al, 2006), evidence suggests that a wide range of searching predators adopt Lévy or Lévy-like walks (Humphries and Sims, 2014;Reynolds, 2013), including humans (Raichlen et al, 2014), while others conform to Brownian movement (examples in Tani et al, 2014). Lévy walks are characterized by a distribution of step lengths with randomized turns equally likely in any compass direction.…”

Section: The Broader Contextmentioning

confidence: 99%

Sit-and-wait versus active-search hunting: A behavioral ecological model of optimal search mode

Ross

Winterhalder

2015

Journal of Theoretical Biology

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We model the behavioral ecology of search mode for randomly moving predator and prey. Active-search is favored at low prey movement velocity, ambush at high prey velocity. Sit-and-wait mode is favored if predator movement is energetically costly. Ambush is favored if faster predator velocity alerts prey or impedes their detection. Optimal predator velocity in active-search mode balances costs against prey movement. a r t i c l e i n f o b s t r a c tDrawing on Skellam's (1958) work on sampling animal populations using transects, we derive a behavioral ecological model of the choice between sit-and-wait and active-search hunting. Using simple, biologically based assumptions about the characteristics of predator and prey, we show how an empirically definable parameter space favoring active-search hunting expands as: (1) the average rate of movement of prey decreases, or (2) the energetic costs of hunter locomotion decline. The same parameter space narrows as: (3) prey skittishness increases as a function of a hunter's velocity, or (4) prey become less detectable as a function of a hunter's velocity. Under either search tactic, encounter rate increases as a function of increasing prey velocity and increasing detection zone radius. Additionally, we investigate the roles of habitat heterogeneity and spatial auto-correlation or grouping of prey on the optimal search mode of a hunter, finding that habitat heterogeneity has the potential to complicate application of the model to some empirical examples, while the effects of prey grouping lead to relatively similar model outcomes. As predicted by the model, the introduction of the horse to the Great Plains and the introduction of the snowmobile to Arctic foraging communities decreased the metabolic costs of active-search and led to a change in normative hunting strategies that favored active-search in place of sit-and-wait hunting.

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“…Power-law distributions of step lengths with diverging variance, a key feature of Lévy processes, are found to describe well the trajectories of immune cells in the brain [11], the displacements of animals [12][13][14][15] and hunter-gatherers [16,17] in their environments, or the travels of modern humans within and between cities [18][19][20][21]. However, the assumption of independence between steps does limit the applicability of genuine Lévy processes for modeling real systems, where non-Markovian effects and correlations can be strong.…”

Section: Introductionmentioning

confidence: 99%

Slow Lévy flights

Boyer

Pineda

2016

Phys. Rev. E

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Among Markovian processes, the hallmark of Lévy flights is superdiffusion, or faster-thanBrownian dynamics. Here we show that Lévy laws, as well as Gaussians, can also be the limit distributions of processes with long range memory that exhibit very slow diffusion, logarithmic in time. These processes are path-dependent and anomalous motion emerges from frequent relocations to already visited sites. We show how the Central Limit Theorem is modified in this context, keeping the usual distinction between analytic and non-analytic characteristic functions. A fluctuation-dissipation relation is also derived. Our results may have important applications in the study of animal and human displacements.

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Evidence of Lévy walk foraging patterns in human hunter–gatherers

Cited by 262 publications

References 39 publications

Subdiffusive motion of bacteriophage in mucosal surfaces increases the frequency of bacterial encounters

Subdiffusive motion of bacteriophage in mucosal surfaces increases the frequency of bacterial encounters

Sit-and-wait versus active-search hunting: A behavioral ecological model of optimal search mode

Slow Lévy flights

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