Nutritional ecology and digestive response to dietary shift in the large South American fox, Pseudalopex culpaeus

Abstract

We tested the role of dietary shifts (from rodents to fruits and to mixed diets) on the nutritional ecology of the culpeo fox Pseudalopex culpaeus, a native canid of South America. We studied the effects of food quality on digestive processes, nutrition, and mass balance, and the implications of diet quality for fox survival. We observed at the end of the nutritional trials that body mass differed significantly between the three diet groups (fruits, rats and mixed diets), while percentage of body mass change differed significantly only in the fruit diet treatment. Foxes fed with fruits consumed more food to meet their dietary and metabolic needs. Across diets, dry-matter as well as energy digestibility increased significantly with diet quality. Also, mean retention time was negatively and significantly correlated with dry-matter intake. We put forth that mixed diet may yield higher assimilation efficiencies and hence higher nutrient intakes than those predicted from the ingestion and assimilation of pure diets (i.e,. only rats, only fruits). We hypothesize that during periods of low availability of mammalian prey, a mixed diet should yield a positive energy/mass balance for the fox. We conclude that temporal and spatial variation in nutrient, energy, and water contents of prey available in a given habitat could have an important effect on fox nutrition, energy use, and mass balance. Finally, we postulate that P. culpaeus could not survive on fruits only past seven days.Key words: nutritional bottleneck, fox, dietary shift, fruit consumption. RESUMENSometimos a prueba el papel del cambio de dieta (desde roedores a frutos y dieta mixta) sobre la ecología nutricional del zorro culpeo Pseudalopex culpaeus, especie nativa de Sudamérica. Estudiamos el efecto de la calidad del alimento sobre los procesos digestivos, nutrición, balance de masas y las implicancias de la calidad de la dieta sobre la sobrevivencia de los zorros. La masa corporal al final de los ensayos nutricionales difirió significativamente entre los tres grupos de dietas (frutos, ratas y dieta mixta), en tanto que el porcentaje de cambio en masa corporal solo fue significativo en el caso de la dieta de frutos. Los zorros alimentados con frutos consumieron más alimento para satisfacer sus necesidades dietarias y metabólicas. Tanto la ingesta de materia seca como la digestibilidad se incrementaron significativamente con la calidad de la dieta. Más aún, el tiempo de retención promedio estuvo negativa y significativamente correlacionado con la ingesta de materia seca. Pensamos que la dieta mixta puede entregar mayores eficiencias de asimilación y por lo tanto mayores ingestas de nutrientes que lo predicho por la ingesta y asimilación de dietas puras (i.e., solo ratas, solo frutos). Proponemos la hipótesis que durante períodos de baja disponibilidad de presas (micromamíferos) una ingesta de dieta mixta podría entregar un balance energía/masa positivo para los zorros. Concluimos que la variación temporal y espacial de nutrientes, energía y contenido d...

Carnivorous mammals: nutrient digestibility and energy evaluation

“…There was a close fit between the estimated and the experimentally determined dietary ME content (Fig. 6) except for diets of low digestibility-in particular, these consisted of two diets fed to foxes that contained native fruits as the only or the dominant ingredient and had CF levels of 12.5-15.2% DM [Silva et al, 2005], and one diet of pine nuts only that contained TDF at 40% DM fed to bears [Pritchard and Robbins, 1990]. When these three diets were excluded, the regression equation for ME estimated was 0.835 ME experimental 14.226 (n 5 87, R 2 5 0.883, Po0.001).…”

“…In the case of several bear diets, a proxy for NfE was calculated using TDF rather than CF values, which were not analyzed in the respective studies. The resulting NfE values were 0%; Harris et al, 1951;Mautz, 1976, 1980;Hamor, 1983;Szymeczko and Skrede, 1991;Ball and Golightly, 1992;Barboza et al, 1994;Skrede, 1995, 1998;Dahlman et al, 2002;Ahlstrom et al, 2003;Silva et al, 2005;Childs-Sanford and Angel, 2006 Felids Acinonyx jubatus, Caracal caracal, Felis concolor, F. margarita, F. pardalis, F. viverrina, F. temminckii, Leptailurus serval, Lynx lynx, L. rufus, Neofelis nebulosa, Panthera leo, P. onca, P. pardus, P. tigris, Prionailurus bengalensis, Uncia uncia Golley et al, 1965;Morris et al, 1974;Wittmeyer Mills, 1980;Barbiers et al, 1982;Hackenburger and Atkinson, 1983;Hamor, 1983;Wynne, 1989;Allen et al, 1995;Crissey et al, 1997;Edwards et al, 2001;Bechert et al, 2002;…”

Comparative trophic ecology of two sympatric canids in the Brazilian Pampa

“…The consumption of invertebrates may be especially important during periods of low availability of vertebrate prey, when both foxes must eat whatever is available for survival. Invertebrate items do not perhaps satisfy all the nutritional requirements of these canids; however, they probably represent an important source of nutritional compounds (Silva et al, 2005). For L. gymnocercus, insects were frequent in the diet, but usually represent small contributions in biomass intake, as observed in Varela et al (2008) for Argentinean Chaco or Canel et al (2016) in Argentinean grasslands.…”

“…There is no information available on the daily ingested biomass for the crab-eating fox and Pampas fox. Therefore, we considered the value of 210 g day À1 , described for culpeo fox, Lycalopex culpaeus (Silva, Jaksic & Bozinovic, 2005), as a parameter for both species once it is similar in size, being just slightly larger (adult weight: 6-8 kg) than them (Di Bitetti et al, 2009). This value was used as the estimated ingested biomass of prey too large to be consumed entirely.…”

Temporal changes in the diet of two sympatric carnivorous mammals in a protected area of south–central Chile affected by a mixed–severity forest fire

“…The sharp decrease in rodents is associated with interannual fluctuation processes in the availability of resources, as has been reported for rodents in the Northern Hemisphere (Hansson and Henttonen, 1988). Consequently, a reconfiguration of the culpeo fox's dietary pattern was observed, which is demonstrated in particular by the disproportionate appearance of arthropods in the dietary range compared to the previous year, greater even than that reported for the same biogeographical area (Zúñiga and Fuenzalida, 2016).The absence of reptile con-sumption compared to the previous year could be the result of a disincentive of its search due to its low energy reward, which would force this canid to prioritize the search for larger prey, as well as a physiological constraint to favor this type of consumption (Silva et al, 2005). This pattern, added to the smaller number of fecal records compared to the previous year, supposes the migration of individuals to habitat patches with a greater supply of resources, a fact facilitated by the wide habitat area of this species (Salvatori et al, 1999).The absence of selectivity in the predation of Cricetidae rodents in the first year is explained by the great availability of this resource, which was observed by the capture success in live traps, which was around 20 % (A. H. Zúñiga, unpublished data).…”