Behavioral mechanisms regulating intake of plant secondary compounds in the woodrat (genus Neotoma)

Herbivores have two foraging strategies to cope with the plant defenses or plant secondary compounds (PSCs) that they face at every meal. A few mammalian herbivores consume a single species of plant almost exclusively. These specialists are predicted to have evolved liver detoxification pathways and capacities specific to the chemistry of a single plant species. In contrast, generalist herbivores consume many different plants and therefore small doses of diverse PSCs. It has been hypothesized that this pattern of ingestion is a mechanism to cope with PSCs by decreasing the cost or risk of over ingesting any single compound. To take advantage of the generalist strategy animals should have behavioral and sensory mechanisms to detect and regulate PSCs.;I examined the role of behavior in regulating PSC intake and examined two possible modifications. The first was the alteration of caching behavior to manipulate volatile compounds by storing food prior to consumption. Three species of rodent herbivores were used to examine the caching hypothesis. One species, Neotoma albigula, used caching to alter the PSC concentration of food, while the others, N. lepida, and N. bryanti did not. We postulated that caching behavior could respond to many environmental constraints and each species tested here may manage the cache for a different constraint.;The second behavioral modification, described as 'the regulation model,' predicted that herbivores reduce meal size as well as increase inter-meal interval (IMI) to safely consume foods with increasing concentrations of PSCs. Two species, a generalist, N. albigula, and a specialist, N. stephensi, were used to examine the hypotheses of the regulation model. Neotoma albigula regulated intake of both known and novel PSCs by modifying meal size in a dose dependent manner. It also had a limited IMI response. Conversely, N. stephensi regulated only the novel PSC and did not modify its spontaneous feeding behavior while consuming its preferred plant. Presumably, the lack of regulation seen on the host diet is due to its greater capacity to detoxify the diet. Behavioral modifications in response to ingestion of PSCs play an important role in herbivore foraging.