Endogenous Nitrogen Excretion by Red Kangaroos (<i>Macropus rufus</i>): Effects of Animal Age and Forage Quality

Munn, Adam J.; Dawson, Terence J.; Hume, I. D.

doi:10.1086/499980

Cited by 8 publications

(2 citation statements)

References 41 publications

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“…Therefore smaller‐bodied, younger herbivores may adopt a different feeding strategy to larger‐bodied, older herbivores in different stages of reproductive output (Clauss et al 2003). The influence of body size and nutritional requirement could apply to both between species differences (Gordon & Illius 1994, Robbins et al 1995), as well as to intraspecific differences between juveniles and adults (Munn et al 2006) and different sexes of mature individuals within the same species (Shannon et al 2006a).…”

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confidence: 99%

Foraging Strategy within African Elephant Family Units: Why Body Size Matters

2011

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Differences in intraspecific foraging strategies have been documented between sexes of strongly dimorphic large herbivore species. Body size implications on diet quality requirements, however, can be extended to within-species age-specific comparisons. We investigated the hierarchical separation of foraging behavior at the scale of plant type, plant species, plant part and vertically through the canopy. For this, we studied African elephant adult females (lower quality diet required) and weaned calves (higher quality diet) within the elephant family unit, which is socially constrained to traverse the landscape together. Grass and browse were used with similar seasonal frequency. Both females and calves tracked the phenology of woody species, including these species in the diet when new growth was available. Forage utilization differed at the plant part level, with calves selecting for less fibrous and more nutritious plant parts (e.g., stripped leaves), while adult females selected branches, bark and roots with greater frequency. There was displacement of females to higher foraging levels in the canopy when these females fed o 3 m away from calves. Elephant family unit foraging strategies were driven by body size, age-specific nutritional requirements and intraspecific competition. This has broader application to other large herbivore species with great variance in intraspecific body size.

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confidence: 99%

Foraging Strategy within African Elephant Family Units: Why Body Size Matters

2011

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“…Today, elemental and stable isotopes analyses are well-stablished tools to assess wild animals’ diet and foraging ecology in a wide range of animal tissues as well as in urine and excreta samples [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. Overall, the elemental analysis of faecal material allows us to gather valuable information as the carbon and nitrogen percentages may indicate the nutritional quality of the diet, i.e., the availability of resources and/or how they are being exploited [ 34 , 35 ].…”

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confidence: 99%

An Experimental Study in Wild Wood Mice Testing Elemental and Isotope Analysis in Faeces to Determine Variations in Food Intake Amount

Navarro-Castilla

Hernández

Barja

2023

Animals

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The analysis of carbon and nitrogen elemental (C, N) and isotopic compositions (δ13C, δ15N) in faeces are considered reliable methodologies for the study of diet in wildlife. Here, we tested the suitability of these techniques to detect variations in the amount of food intake. We captured wild wood mice (Apodemus sylvaticus) with Sherman live traps where bait access was initially free, and later it was experimentally limited inside by four different devices to cause intended variations in the amount ingested. The total C and N (%) and stable δ13C and δ15N isotopic values were determined for the bait and in mice faecal samples. Faecal values were lower than bait ones except for N, likely due to animal matter ingested before capture. No significant differences in total C, N and δ13C were found due to individual traits. However, breeding males showed higher δ15N values than breeding females, probably due to differences in energy and protein demands between both sexes during the breeding season. Only δ13C detected food intake variations (≥2 g). Despite further research being needed, these results initially support the potential of δ13C to provide information on the amount ingested, thus being useful to complement trophic ecology studies.

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Modelling digestive constraints in non-ruminant and ruminant foregut-fermenting mammals

Munn

Streich

Hummel

et al. 2008

Comparative Biochemistry and Physiology Part A: Molecular &

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It has been suggested that large foregut-fermenting marsupial herbivores, the kangaroos and their relatives, may be less constrained by food intake limitations as compared with ruminants, due mainly to differences in their digestive morphology and management of ingesta particles through the gut. In particular, as the quality of forage declines with increasing contents of plant fibre (cellulose, hemicelluloses and lignin; measured as neutral-detergent fibre, NDF), the tubiform foregut of kangaroos may allow these animals to maintain food intakes more so than ruminants like sheep, which appear to be limited by fibrous bulk filling the foregut and truncating further ingestion. Using available data on dry matter intake (DMI, g kg(-0.75) d(-1)), ingesta mean retention time (MRT, h), and apparent digestibility, we modelled digestible dry matter intake (DDMI) and digestible energy intake (DEI) by ruminant sheep (Ovis aries) and by the largest marsupial herbivore, the red kangaroo (Macropus rufus). Sheep achieved higher MRTs on similar DMIs, and hence sheep achieved higher DDMIs for any given level of DMI as compared with kangaroos. Interestingly, MRT declined in response to increasing DMI in a similar pattern for both species, and the association between DMI and plant NDF contents did not support the hypothesis that kangaroos are less affected by increasing fibre relative to sheep. However, when DEI was modelled according to DDMIs and dietary energy contents, we show that the kangaroos could meet their daily maintenance energy requirements (MER) at lower levels of DMI and on diets with higher fibre contents compared with sheep, due largely to the kangaroos' lower absolute maintenance and basal energy metabolisms compared with eutherians. These results suggest that differences in the metabolic set-point of different species can have profound effects on their nutritional niche, even when their digestive constraints are similar, as was the case for these ruminant and non-ruminant foregut fermenters.

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Endogenous Nitrogen Excretion by Red Kangaroos (Macropus rufus): Effects of Animal Age and Forage Quality

Cited by 8 publications

References 41 publications

Foraging Strategy within African Elephant Family Units: Why Body Size Matters

Foraging Strategy within African Elephant Family Units: Why Body Size Matters

An Experimental Study in Wild Wood Mice Testing Elemental and Isotope Analysis in Faeces to Determine Variations in Food Intake Amount

Modelling digestive constraints in non-ruminant and ruminant foregut-fermenting mammals

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