A multivariate perspective of resource acquisition behaviours in bighorn sheep

Abstract

Quantifying variation in individual resource acquisition and allocation to costly life-history functions is critical to understand the evolution of life-histories. Individuals should adaptively respond to changes in resource requirements throughout their lifetime through flexibility in resource acquisition behaviours. Empirical investigation of behavioural adjustments in wild settings are scarce and rarely consider more than one behaviour. Resource acquisition, however, involves several behaviours and should be considered in a multivariate framework. We measured four resources acquisition behaviours – bite rate, rumination rate, chews per bolus and bolus processing time in bighorn sheep, Ovis canadensis . We then tested whether individuals adjust these behaviours as expected based on individual differences in resource allocation to lactation and annual mass gain. Using a multivariate mixed effects model, we also evaluated the prediction that bite rate and rumination behaviours are repeatable and show strong covariation among individuals. Both bite rate and rumination effort increased with allocation to lactation. Allocation to mass gain, however, was positively correlated with rumination effort but not with bite rate. Rumination behaviours also showed significant variation with sex and mass, suggesting potential morphological and/or physiological constraints. Although all four behaviours were significantly repeatable, contrary to our predictions, bite rate was not significantly correlated with rumination behaviours among individuals. This study highlights strong correlations between expected resource allocation to costly life-history functions and multiple resource acquisition behaviours. There was, however, no evidence that variance in multiple resource acquisition behaviours originates from a single axis of variation among individuals. • Bite rate and rumination effort increased with resource allocation to lactation. • Only rumination effort increased with mass gain. • Individual level repeatability of resource acquisition behaviours was significant. • Resource acquisition behaviours were not correlated among individuals.