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From Microbes in Motion to Pumas in Pursuit of Prey: Foraging Phenomena in Interactive Multi-agent Systems

Creative Commons 'BY' version 4.0 license

While foraging phenomena have historically been a focus of ecology, they can be described as search processes carried out by one or multiple agents in a landscape characterised by a resource distribution. As a result, tools from statistical physics can be used to study foraging phenomena. The integration of statistical physics as a set of tools to both describe patterns observed in foraging processes and understand the underlying mechanisms that give rise to these patterns has enabled the development of robust theory as well as the expansion of the scope of foraging to include applications in intracellular processes, human cognitive behaviour, and even robotics.

Treating foraging processes as undertakings by a single foraging agent in a resource environment has laid the foundation for a significant amount of our understanding of foraging. However, these approaches fail to capture the complexities of real foraging phenomena which arise from the fact that foraging agents do not exist independent of their environment. The logical first order step to rectify this is to consider foraging processes carried out by multiple interacting agents. This dissertation describes complex, emergent phenomena in three different systems resulting from interactions between multiple foraging agents.

First, I present a minimal, one-dimensional analytical model that describes emergent pattern formation in a community of phototactic bacteria moving towards a directional light source. During phototaxis---essentially, foraging for light---interactions between individual bacteria result in emergent community-level spatial organisation, leading to the formation of finger-like projections at the propagating front. We developed a one-dimensional analytical model which describes the dynamics of this pattern formation and predicts critical parameters that limit finger formation. This model also predicts the loss of instabilities in mutant phenotypes lacking a key photoreceptor.

Second, I present a framework to use foraging theory to investigate the dynamics of vocal interactions between human infants and their adult caregivers. By analysing day-long recordings of infant and caregiver vocalisations in naturalistic settings over the infants' first year, we demonstrated support for the hypothesis that infants and their adult caregivers are foraging in an acoustic space for sounds that have social value. Our findings also provide evidence that vocal interactions between infants and caregivers modify these foraging patterns.

Finally, I present a computational model to study the diversity of foraging strategies employed by terrestrial carnivore predators. Mammalian carnivores' foraging strategies include hunting, scavenging, and kleptoparasitism (stealing). However, despite the prevalence of literature on predator-prey systems, the factors that result in the deployment of these strategies and their effects on predator-prey systems are not well understood. In this study, we use an energetics approach to investigate how a focal predator's interactions with potential prey and other predators constrain the use of these strategies. Our results predict the dependence of predator foraging strategy on predator energetics as well as the body sizes of the focal predator, prey, and potential competitors. In particular, our predictions for the boundaries between hunting and alternative foraging strategies (scavenging and stealing) show remarkable agreement with observational data. By employing dimensional reduction, we are also able to accurately describe the phase transition from a state where the focal predator relies predominantly on hunting to a state where the focal predator largely relies on scavenging and stealing.

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