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

Abstract

In adaptive terms, animals are subject to challenges imposed by their environment. To address physiological patterns in wild mammals, the non‐invasive study of glucocorticoid hormones has become the main approach through two well‐defined conceptual frameworks: one is related to stress responses, whereas another refers to the glucocorticoids as physiological mediators of the allostatic load, necessary for the maintenance of homeostasis. A key factor to analyse the physiology of wild animals is to understand the relationship between energetic demands and nutritional attributes. The objective of this study was to assess the influence 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, we quantified nitrogen content and cortisol metabolite concentrations in fresh faeces. Samples were collected in two contrasting seasons (summer and winter, representing the breeding and non‐breeding seasons respectively). Summer was identified as the period of highest diet quality and energy mobilization, in both sexes and populations. We found quadratic relationships between cortisol levels and nitrogen percentage, which we hypothesize corresponds to two different factors: one of an energetic‐nutritional nature (during winter, the non‐reproductive season), and the other of an energetic‐reproductive nature (during summer, the reproductive season). Our evidence suggests variation in the administration of energy resources in guanacos in response to internal and external stimuli, giving rise to a novel Biphasic Model of energy demand. Our results reinforce the knowledge of the adaptive eco‐physiological attributes of guanaco, and we describe a new conceptual model which explains the energy management patterns for this species and possibly for other ungulates, within the breeding and non‐breeding seasons.

Cabo Dos Bahías y el manejo del guanaco en la Patagonia argentina

“…Se colectaron ~20 boñigas por bosteadero y se conservaron en bolsas de papel. El contenido de nitrógeno en fecas o nitrógeno fecal (N fecal) es considerado un indicador útil de la calidad relativa de la dieta de una población en distintas estaciones del año, o distintos años, así como de poblaciones de la misma especie expuestas a condiciones ambientales similares (Leslie and Starkey 1987;Gregorio et al 2019). Además de las 13 muestras de 2007 y 2008 mencionadas previamente, se incluyeron muestras colectadas en verano 2014 (n=2), otoño 2016 (n=6), invierno 2016 (n=17), verano 2016 (n=12) y otoño 2017(n=8).…”

Male aggressiveness in a polygynous ungulate varies with social and ecological context

“…Considering that aggressiveness is influenced by resource availability (Fattorini, et al, 2018;Sirot, 2000;Taillon & Côté, 2007) (Jurgensen, 1985;Panebianco, 2019;Young & Franklin, 2004b). Further evidence in favour of this argument comes from the relatively high concentration of faecal cortisol metabolites observed in guanaco males during the post-mating period of 2014 (Panebianco, 2019), suggesting that individuals had higher energy demands during this time (Gregorio et al, 2019;Romero et al, 2009). Similarly, in other ungulate species, such as Apennine chamois (Rupicapra pyrenaica ornata) and white-tailed deer (Odocoileus virginianus), food depletion influenced intraspecific social behaviour by increasing aggression (Fattorini, et al, 2018;Taillon & Côté, 2007) and endocrine correlates (Fattorini, et al, 2018), in accordance with competition theory (Sirot, 2000).…”

“…In both sedentary and migratory populations, these main social units are similar, with the exception that mixed groups are primarily found in migratory populations in varying proportions throughout the annual cycle (Franklin, 1983). This wild camelid has been successfully used as an ecological model of adaptation due to anatomical, physiological and behavioural traits that allow it to inhabit hostile environments (Franklin, 1983;González et al, 2006;Gregorio et al, 2019;Marino & Baldi, 2008;Ovejero et al, 2016;Taraborelli et al, 2012).…”

Hunting Site Behaviour of Sympatric Common Buzzard Buteo buteo and Rough-Legged Buzzard Buteo lagopus on Their Wintering Grounds

“…In addition to the negative impact of low temperatures, the lack or limited availability of food also leads to considerable energy losses in animals and possibly their death [1][2][3][4]. This is why an adequate supply of energy in the form of high-calorie food [5][6][7] or sufficient amounts of other food [8] is so important during this season. Vertebrates wintering in the northern regions of the Northern Hemisphere adjust their foraging behavior accordingly to compensate for great losses of energy and/or to prepare for winter food deficiency.…”