Respiratory reference values for bottlenose dolphins (Tursiops spp.) and its importance for conservation

Abstract

Respiratory disease is one of the main causes for morbidity and mortality in cetaceans, which highlights the importance of understanding normal lung function and how it may impede homeostasis, and diving capacity. In addition, the use of breathing frequency as a proxy for metabolic rate requires a better estimate of the normal range of tidal volume, respiratory flow, and breath durations. In the current study, we use data on clinically healthy bottlenose dolphins (Tursiops spp.) collected over a decade to define how lung function varies with body mass, age, and sex while in water or during voluntary beaching. The data show that tidal volume consistently varies with body mass both during spontaneous and forced breaths both in water and while beached. Both peak expiratory and inspiratory flow varies with body mass, but also in some circumstances with sex and age. Total and inspiratory breath durations only varied with body mass during forced breaths on land. Expired tidal volume varied with both body mass and either total or expiratory breath duration. These data provide baseline for respiratory function in healthy bottlenose dolphins and suggest that either total or expiratory breath duration provide a useful proxy for tidal volume.