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

Abstract

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.

Can animal performance be predicted from short-term grazing processes?

“…Animals may have selected areas for grazing that departed significantly from the average for the inter-tussock stratum. Novel results by Bonnet et al (2015) confirmed that heifers take a significant proportion of bites from tussocks (~30% of bites), and these proportions show variation over time. The assumption of non-selective grazing exclusively within the inter-tussock is not a failure of our main hypothesis, but of our original conceptual model used to test the hypothesis.…”

Foraging Behavior of Goats Browsing in Southern Mediterranean Forest Rangeland

“…The animal familiarization procedure aims to accustom the flock to the permanent presence of an unfamiliar person. This mutual familiarization procedure was detailed by Bonnet et al and Meuret and Provenza [25,26]. The observer is considered fully familiarized with the animal if he can get as close as 0.5 to 1.5 m, providing that it does not hamper the spontaneous movements of the goats [27][28][29].…”

Influencia de las dimensiones de las ramas de árboles forrajeros en el aprovechamiento por rumiantes

“…Si, además, los tallos de las diversas plantas arbóreas forrajeras poseen elevados contenidos de fibra responsable de su rigidez (Valenciaga & Chongo, 2004) e inversamente ligada al consumo de alimentos (Forbes, 2000;Karsli & Russell, 2002) y también, según Laca, Shipley y Reid (2001) e Ingram et al (2013), existen muchas interacciones entre otros elementos morfológicos de las plantas, que se denominan "características anticalidad", así como del animal, del manejo de ambos y de las condiciones ambientales, entonces, determinar cuánto es consumido de una planta arbórea por los animales en el pastoreo es un procedimiento imprescindible y complejo (Bonnet et al, 2015), lo que sugiere la necesidad de investigaciones que generen tales informaciones para el manejo sostenible de la vegetación y que puedan ser aplicadas para adoptar estrategias de suplementación (González-Pech, Torres-Acosta & Sandoval-Castro, 2014). Se sabe, además, que los rumiantes pueden aprender de experiencias acumuladas para seleccionar los forrajes que consumen (Fisher, 2002).…”