Stephens & Foraging - Behavior and Ecology - Chapter 5 pps

Part II Processing, Herbivory, and Storage [...]... )]} (5. 4) The behavior of equation (5. 4) is qualitatively similar to that of equation (5. 3) and is illustrated by plotting HT as a function of R1 and R2 (fig 5. 5) In all cases, increasing Ri increases Hi and decreases H j , where i = j This occurs because resource 1 (or resource 2) reduces the forager’s consumption of resource 2 (or resource 1) through both external and internal handling times By handling... Structure and Function Foraging ecologists often consider gut morphology, digestion and absorption biochemistry, and the flow rate of food through the gut as constraints on foraging behavior (Stephens and Krebs 1986) But digestive physiologists have long known that diet composition influences gut structure and gut Food Acquisition, Processing, and Digestion function in a flexible way (Afik et al 19 95; Karasov... that undergo extreme bouts of feast and famine: sit -and- wait -foraging snakes that feed at infrequent intervals, but consume 25% –160% of their body mass when they do Examples include the boa constrictor (Boa constrictor), the Burmese python (Python molurus), and the sidewinder rattlesnake (Crotalus cerastes) (Secor and Diamond 19 95, 2000; Secor 2003; but see Starck and Beese 2002; Starck 2003; Starck... manipulations (Abrahams and Dill 1989; Nonacs and Dill 1990; Todd and Cowie 1990; Brown 1988) or the economic concept of marginal rates of substitution (Brown 1988; Brown, Kotler, and Valone 1994; Mitchell et al 1990) The most powerful and flexible approach is that of dynamic state variable models, described in chapters 1 and 7 153 154 Christopher J Whelan and Kenneth A Schmidt Linking Ecological and Physiological... continuous-flow, stirred-tank reactors for a given reactor volume and when reactions are catalytic, but continuous-flow, stirred-tank reactors outperform plug-flow reactors when reactions are autocatalytic They also showed that a digestive system consisting of a continuous-flow, stirred-tank reactor/plug-flow reactor series was superior in performance on the low-quality foods eaten by foregut fermenters (Alexander... external handling time is independent of the forager’s overall harvest rates on resources 1 and 2 However, the internal handling time increases with harvest rates and Figure 5. 4 Graphical results of Whelan and Brown’s (20 05) foraging model incorporating both external (preconsumptive) and internal (postconsumptive) handling of food (A) Harvest rate as a function of resource abundance when both external and. .. invertebrates and vertebrates; and continuous-flow, stirred-tank reactors are analogues for the large chambers found in foregut and hindgut fermenters Models of actual animal guts often allow different idealized reaction chambers to be connected serially For instance, a ruminant may be modeled as a large continuous-flow, stirred-tank reactor serially followed by a plug-flow reactor and then a small continuous-flow,... (Karasov 1996; Whelan et al 2000) and helps foragers meet their metabolic demands in the face of a shifting and sometimes unpredictable resource base 5. 4 Integrating Ecological and Physiological Processes This section examines a number of ways to integrate digestive physiology and foraging ecology To begin, we compare the disparate cost accounting practices of foraging ecologists and digestive physiologists... will increase our understanding of both ecological and physiological processes Costs of Foraging Foraging ecologists and digestive physiologists focus on different aspects of the costs of foraging These differences reflect distinct perspectives on the intrinsic and extrinsic factors that influence foraging To a foraging ecologist, intrinsic factors include the forager’s search and attack strategies, habitat... senses and the body help to explain why palatability changes within meals and from meal to meal (Provenza 1996; Provenza, Villalba, Dziba et al 2003) Flavor-, nutrient-, and toxin-specific satiety refer to the decrease in preference for the flavor of a food during and after eating because of interactions involving a food’s flavor and postingestive feedback from cells and organs in response to nutrients and . instance, that plug-flow reactors outper- form bothbatch and continuous-flow, stirred-tank reactorsfor a givenreactor volumeand when reactionsarecatalytic, but continuous-flow,stirred-tankre- actors outperform. (Forbes 2001; Whelan and Brown 20 05; and see below). While this chapter focuses on the interplay between foraging ecology and digestive physiology, we first consider the role of ecology, particularly. some in- vertebrates, including hydras and coelenterates; plug-flow reactors are ana- logues for the tubular guts found in most multicellular invertebrates and vertebrates; and continuous-flow,