Linking diet quality and energy demand in free-living guanacos: an eco-physiological innovative approach

GREGORIO PABLO; PANEBIANCO A.; RAMIRO J. A. OVEJERO; TARABORELLI, P; MORENO, P. G; SCHROEDER, N. M; LEGGIERI, L. R; MAROZZI, A; CARMANCHAHI P.

JOURNAL OF ZOOLOGY (1987)

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2019

0952-8369

In adaptive terms, the animals are subject to challenges imposed by the environment. To address physiological patterns in wild mammals, the non-invasive study of glucocorticoid hormones becomes the main approach through two well-defined conceptual frameworks: one is related to the stress responses, while another refers to the glucocorticoids as physiological mediators of the allostatic load, necessary for the maintenance of homeostasis. A key factor to analyse the energy demands is the understanding of the relationship with the nutritional attributes. Nitrogen is a component of proteins and its content in faeces is the most frequently used indicator of diet quality in ruminants.The objective of this study was to assess the incidence of diet quality on physiological mediators of energy mobilization in two populations of wild guanacos (Lama guanicoe) from Northern Patagonia. In order to evaluate energy mobilization and its relationship with diet quality, nitrogen content and cortisol metabolite concentrations were quantified in fresh faeces. Samples were collected in two contrasting seasons (winter and summer, representing the non-breeding and breeding seasons, respectively). Summer was identified as the period of highest diet quality and energy mobilization, in both sexes and populations. Quadratic relationships were detected between cortisol levels and nitrogen percentage, which could correspond to two different factors that would be operating: one of energetic-nutritional nature (during winter, the non-reproductive season), and another of energetic-reproductive nature (during summer, the reproductive season). This evidence shows changes in the administration of energy resources in the guanaco, giving rise to a new conceptual framework, the Biphasic Model of energy demand. These results reinforce the knowledge of the adaptive eco-physiological attributes of guanaco, and the new conceptual model may be explaining the energy management patterns for this specie and possibly for other ungulates, within the breeding and non-breeding seasons.