Continuous bite monitoring: a method to assess the foraging dynamics of herbivores in natural grazing conditions.

Accurate estimates of bite mass and variations in the short-term intake rate of grazing herbivores has been historically considered as a fundamental methodological difficulty, a difficulty that increases with the complexity of the feeding environment. Improving these methodologies will help understand foraging behaviours in natural grazing conditions, where habitat structure and interactions among different forages influence feeding decisions and patterns. During the past 30 years, we have been developing the 'continuous bite-monitoring' method, an observational method that allows continuous assessment of foraging behaviours, including bite mass, instantaneous intake rate and food selection, in simple to complex feeding environments. The centrepiece of the method is a 'bite-coding grid' where bites are categorised by structural attributes of the forage to reflect differences in bite masses. Over the years, we have been using this method with goats, sheep, llamas and cattle across a range of different habitats. After reviewing the development of the method, we detail its planning and execution in the field. We illustrate the method with a study from southern Brazilian native Pampa grassland, showing how changes in the forages consumed by heifers strongly affect short-term intake rate during meals. Finally, we emphasise the importance of studying animals grazing in their natural environments to first identify the relevant processes that can later be tested in controlled experiments. In heterogeneous feeding environments, herbivores constantly modify their foraging behaviour to cope with variations in the external environment and to account for changes of their internal milieu. Assessing the variation of these behaviours, particularly the intake rate of food, has long been considered challenging. We present a methodology based on continuous bite monitoring through direct observation that help address this difficulty and facilitates the study of the foraging strategies of herbivores under natural grazing conditions. [ABSTRACT FROM AUTHOR]