Self-organization of foraging behaviour: From simplicity to complexity without goals

Abstract

A herbivore faces challenges while foraging-angoing changes in its physiological condition along with variation in the nutrient and toxin concentrations of foods, spatially and temporally-that make selecting a nutritious diet a vital affair. Foraging behaviours arise from simple rules that operate across levels of resolution from cells and organs to individuals and their interactions with social and physical environments. At all these levels, behaviour is a function of its consequences: a behaviour operating on the environment to induce changes is itself changed by those events. Thus, behaviour emerges from its own functioning-behaviour selforganizes-not from that of its surroundings. This ostensible autonomy notwithstanding, no self-organizing system (cell, organ, or individual) is independent of its environs because existence consists of an ongoing exchange of energy and matter. According to this view, the notion of cause and effect is replaced with functional relationships between behaviours and environmental consequences. Changes in physical environments alter the distribution, abundance, nutritional, and toxicological characteristics of plants, which affect food preference. Social interactions early in life influence behaviour in various ways: animals prefer familiar foods and environments, and they prefer to be with companions. Animals in unfamiliar environments often walk farther, ingest less food, and suffer more from malnutrition and toxicity than animals in familiar environments. An individual's food preferences-and its ability to discriminate familiar from novel foods-arise from the functional integration of sensory (smell, taste, texture) and postingestive (effects of nutrients and toxins on chemo-, osmo-, and mechano-receptors) effects. The ability to discriminate among foods is critical for survival: all problems with poisonous plants are due to an inability to discriminate or a lack of alternatives. Animals eat a variety of foods as a result of nearing or exceeding tolerance limits for sensory and postingestive effects unique to each food. After eating any food too frequently or excessively, the likelihood increases that animals will eat alternative foods owing to exceeding sensory-, nutrient-, and toxin-specific tolerance limits. Cyclic patterns of intake of a variety of foods reflect seemingly chaotic interactions among flavours, nutrients, and toxins interacting along continua.

Self-medication and homeostatic behaviour in herbivores: learning about the benefits of nature’s pharmacy

“…The transition from the unfamiliar to the familiar begins at conception and in utero with mother and continues after birth with mother and peers. Lessons learned early in life from a mother create a dichotomy between the familiar and the unfamiliar (novel), which is essential for survival (Provenza, 1995;Provenza et al, 1998 and2003). Animals prefer familiar to novel foods and environments and they prefer to be with companions as opposed to strangers .…”

Diet selection and animal state: an integrative framework

“…There is disagreement about the quantity of food that is needed to produce sufficient change in internal state to cause a consequent change in diet selection. It has been suggested (Provenza et al 1998) that the short-term systemic fluctuations in the levels of metabolites and hormones that occur during a meal are sufficient to affect the composition of the next meal to be selected. But the evidence cited in favour of this view, which is that of de Jong (1981), is precisely that which refutes the argument.…”

A Pharm-Ecological Perspective of Terrestrial and Aquatic Plant-Herbivore Interactions

“…For example, previous ecological exposure to PSMs increases tolerance to those PSMs, but may decrease tolerance to novel PSMs (Gustafsson and Hansson, 2004;Sorensen et al, 2005b). Memory of the positive and negative experiences of exceeding thresholds to nutrients and PSMs via conditioned food aversions can also influence foraging phenotypes (Provenza et al, 1998).…”

“…It has been widely observed that the quality, quantity, and complexity of nutrients and PSMs and the learned responses to these dietary components can mediate the foraging patterns of herbivores (Amsler, 2008;Behmer, 2009;Hay and Fenical, 1988;Paul and Vanalstyne, 1992;Provenza et al, 1998;Provenza et al, 2003;Simpson and Raubenheimer, 2001). Although the general concepts of pharmacology were introduced to ecologists to explain plant-herbivore interactions 38 years ago (Freeland and Janzen, 1974), the empirical use of pharmacology to understand mechanisms driving foraging patterns in any system is limited (Haley et al, 2008;Magnanou et al, 2009;Marsh et al, 2006b;McLean and Duncan, 2006;Sotka et al, 2009).…”