Plant secondary metabolites alter the feeding patterns of a mammalian herbivore (Neotoma lepida)

Abstract

Mammalian herbivores are predicted to regulate concentrations of ingested plant secondary metabolites (PSMs) in the blood by modifying the size and frequency of feeding bouts. It is theorized that meal size is limited by a maximum tolerable concentration of PSMs in the blood, such that meal size is predicted to decrease as PSM concentration increases. We investigated the relationship between PSM concentration in the diet and feeding patterns in the herbivorous desert woodrat (Neotoma lepida) fed diets containing phenolic resin extracted from creosote bush (Larrea tridentata). Total daily intake, meal size and feeding frequency were quantified by observing the foraging behavior of woodrats on diets containing increasing concentrations of creosote resin. Desert woodrats reduced meal size as resin concentration in the diet increased, resulting in an overall reduction in daily intake and regulation of resin intake. Moreover, desert woodrats were able to detect resin concentrations in the diet and regulate the intake of resin very rapidly. We suggest that the immediate and sustained ability to detect and regulate the intake of resin concentrations during each foraging bout provides a behavioral mechanism to regulate blood concentrations of resin and allows desert woodrats to make "wise" foraging decisions.

The dilemma of foraging herbivores: dealing with food and fear

“…Many compounds can cause physiological damage, force a reduction in food intake or may cause starvation (Bryant and Kuropat 1980;Sorensen et al 2005a;Shipley et al 2012). Ultimately, plant defences can lower herbivore reproductive success (DeGabriel et al 2009).…”

“…As toxin concentration in food increases, captive herbivores eat more slowly in smaller feeding bouts (Wiggins et al 2003;Sorensen et al 2005a;Wiggins et al 2006a;Torregrossa and Dearing 2009), and eat less in total (Marsh et al 2006). Free-ranging herbivores quit food patches earlier and alter their choice of food patches.…”

Ambient Temperature Influences Diet Selection and Physiology of an Herbivorous Mammal, Neotoma albigula

“…Generalists appear to be more sensitive to concentration changes and less able to cope with increases in PSC concentrations from a single plant species in their diet than specialists (Sorensen et al 2005a). Specialist herbivores are predicted to have evolved efficient biochemical mechanisms to deal with the PSCs in their diet (Green et al 2004;Sorensen et al 2005aSorensen et al , 2005bHaley et al 2007) and therefore are likely have a physiological tolerance in excess of the average concentration ingested daily. Thus, specialists are predicted to be able to cope with increases in toxicity of their host plant.…”

Modeling trade‐offs between plant fiber and toxins: a framework for quantifying risks perceived by foraging herbivores

“…Herbivores maintain systemic toxin levels behaviorally by regulating total food intake, meal size, timing of consumption, and mixing diets (Sorensen et al 2005a, Wiggins et al 2006. Pygmy rabbits, with their higher capacity to detoxify monoterpenes, were able to maintain their daily intake of rabbit pellets as the concentration of cineole increased over 5%, whereas mountain cottontails began to reduce intake when cineole concentration was only 1% (Shipley et al 2012).…”