植食性小哺乳类营养生态学的研究：高原鼠兔的食物选择模式与食物质量

本文报道了高原鼠兔(Ochotona curzoniae)的食物模式,食物选择指数及食物项目的营养成分,并探讨食物质量与食物选择的关系。高原鼠兔主要选食双子叶植物叶片。食物组成与饲料可利用量的比较分析,揭示出高原鼠兔对各种食物项目的选择程度。在排除其它营养因子的作用后,复回归分析的结果表明,食物百分率与磷含量之间具有显著的正相关。各种食物项目不同营养成分与食物百分率之间相关关系不一致。从而进一步验证了食物选择决定于饲料可利用量和食物质量的假设。     

Nutritional ecology provides insights into competitive interactions between closely related Martes species

1. Closely related predator species often share several prey items, making it hard to differentiate the effects on their feeding habits of variation in food availability and of competition. We hypothesised that we could overcome this obstacle by quantifying and comparing nutritional niches.
2. We reviewed dietary studies that assessed the relative bulk of each food item, as either per cent biomass or per cent mean volume, in the diet of two closely related species, pine marten Martes martes and stone marten Martes foina, and calculated the nutrient profiles (intakes of protein, lipids and carbohydrates) of each diet.
3. Both martens’ diets were tightly clustered (mean values: 47% of energy from protein, 39% from lipid, and 14% from carbohydrate). In allopatry, the nutritional niches of the two species did not differ, but in sympatry, the stone marten ate more carbohydrates and less protein than the pine marten. In allopatry, the protein intake of the stone marten remained high (45–52%) in very different habitats, from cultivated lowland to Alpine forests.
4. Our data suggest that stone marten frugivory may, at least partially, be the result of interspecific competition. By analysing dietary data in the framework of nutritional ecology, we could compare the feeding requirements of pine martens and stone martens more effectively than by using classical estimates of trophic niche overlap at the food item level. This approach may help to shed light on the trophic relationships of other competing species.

     

A review of feeding and nutrition of herbivorous land crabs: adaptations to low quality plant diets

This paper reviews the nutritional ecology, the digestive physiology, and biochemistry of herbivorous land crabs and the adaptations that they possess towards a diet of plant material. Land crab species that breathe air and forage out of water can be divided into three feeding specialisations: primarily carnivorous, deposit feeders feeding on micro-organisms and organic matter in the sediment, and herbivores consuming mainly plant material and its detritus. The last forms the focus of this review. The diets of the herbivores are low in nitrogen and high in carbon, are difficult to digest since they contain cellulose and hemicellulose, and may disrupt digestion due to the presence of tannins. Herbivorous crustaceans are able to efficiently utilise plant material as their primary nutrient source and are indeed able to meet their nitrogen requirements from it. Herbivorous land crabs display a range of adaptations towards a low nitrogen intake and these are discussed in this review. They also appear to endogenously produce cellulase and hemicellulase enzymes for the digestion of cellulose and hemicellulose. Generalised and specific adaptations allow them to inhibit the potentially negative digestive effects of tannins. To digest plant material, they possess a plastic digestive strategy of high food intake, short retention time, high assimilation of cell contents, and substantial digestion of cellulose and hemicellulose.     

Nutritional quality of gorilla diets: consequences of age,sex, and season

We tested the effects of age, sex, and season on the nutritional strategies of a group of mountain gorillas (Gorilla beringei) in the Bwindi Impenetrable National Park, Uganda. Through observations of food intake of individual gorillas and nutritional analyses of dietary components over different seasons and environments, we estimated nutrient intake and evaluated diet adequacy. Our results suggest that the nutritional costs of reproduction and growth affect nutrient intake; growing juveniles and adult females ate more food and more protein per kilogram of metabolic body mass than did silverbacks. The diets of silverback males, adult females, and juveniles contained similar concentrations of protein, fiber, and sugar, indicating that adult females and juveniles did not select higher protein foods than silverbacks but rather consumed more dry matter to ingest more protein. Juveniles consumed more minerals (Ca, P, Mg, K, Fe, Zn, Mn, Mo) per kilogram of body mass than adult females and silverback males, and juveniles consumed diets with higher concentrations of phosphorous, iron, and zinc, indicating that the foods they ate contained higher concentrations of these minerals. Seasonally, the amount of food consumed on a dry weight basis did not vary, but with increased frugivory, dietary concentrations of protein and fiber decreased and those of water-soluble carbohydrates increased. Energy intake did not change over the year. With the exception of sodium, gorillas ate diets that exceeded human nutrient requirements. A better understanding of the relative importance of food quantity and quality for different age–sex classes provides insights into the ways in which gorillas may be limited by food resources when faced with environmental heterogeneity.     

Feeding preferences and nutritional niche of wild water buffalo (Bubalus arnee) in Koshi Tappu Wildlife Reserve,Nepal

The nutritional characteristics of food resources play an important role in the foraging behavior of animals and can provide information valuable to their conservation and management. We examined the nutritional ecology of wild water buffalo (Bubalus arnee; hereafter “buffalo”) in the Koshi Tappu Wildlife Reserve of Nepal during autumn using a multidimensional nutritional niche framework. We identified 54 plant species as being foraged by buffalo. We found that buffalo consumed graminoids and forbs 2–3 times more frequently than browse items. Proximate analyses of the 16 most frequently foraged plants indicated that buffalo diets were highest in carbohydrate (40.41% ± 1.82%) followed by crude protein (10.52% ± 0.93%) and crude fat (1.68% ± 0.23%). The estimated macronutrient balance (i.e., realized nutrient niche) of the buffalo diet (20.5% protein: 72.8% carbohydrate: 6.7% lipid) was not significantly different than the average balance of all analyzed food items based on 95% confidence regions. Our study suggests that buffalo are likely macronutrient specialists, yet may be generalists in the sense that they feed on a wide range of food items to achieve a nutrient balance similar to that available in forage items. However, the four most frequently consumed items tended to be higher in protein energy than less frequently consumed foods, suggesting some preference for higher protein forage relative to relatively abundant carbohydrates. Although limited in scope, our study provides important information on the nutritional ecology of buffalo, which may be useful for the conservation and management of this endangered species.     

Voluntary intake and digestibility in horses: effect of forage quality with emphasis on individual variability

Food intake is a key biological process in animals, as it determines the energy and nutrients available for the physiological and behavioural processes. In herbivores, the abundance, structure and quality of plant resources are known to influence intake strongly. In ruminants, as the forage quality declines, digestibility and total intake decline. Equids are believed to be adapted to consume high-fibre low-quality forages. As hindgut fermenters, it has been suggested that their response to a reduction in food quality is to increase intake to maintain rates of energy and nutrient absorption. All reviews of horse nutrition show that digestibility declines with forage quality; for intake, however, most studies have found no significant relationship with forage quality, and it has even been suggested that horses may eat less with declining forage quality similarly to ruminants. A weakness of these reviews is to combine data from different studies in meta-analyses without allowing the differences between animals and diets to be controlled for. In this study, we analysed a set of 45 trials where intake and digestibility were measured in 21 saddle horses. The dataset was analysed both at the group (to allow comparisons with the literature) and at the individual levels (to control for individual variability). As expected, dry matter digestibility declined with forage quality in both analyses. Intake declined slightly with increasing fibre contents at the group level, and there were no effects of crude protein or dry matter digestibility on intake. Overall, the analysis for individual horses showed a different pattern: intake increased as digestibility and crude protein declined, and increased with increasing fibre. Our analysis at the group level confirms previous reviews and shows that forage quality explains little of the variance in food intake in horses. For the first time, using mixed models, we show that the variable 'individual' clarifies the picture, as the horses showed different responses to a decrease in forage quality: some compensated for the low nutritional value of the forages by increasing intake, few others responded by decreasing intake with declining forage quality, but not enough to cause any deficit in their energy and protein supplies. On the whole, all the animals managed to meet their maintenance requirements. The individual variability may be a by-product of artificial selection for performance in competition in saddle horses.     

Nutritional Ecology of <Emphasis Type="Italic">Ateles chamek</Emphasis> in lowland Bolivia: How Macronutrient Balancing Influences Food Choices

All free-living animals must make choices regarding which foods to eat, with the choices influencing their health and fitness. An important goal in nutritional ecology is therefore to understand what governs animals’ diet selection. Despite large variation in the availability of different food items, Peruvian spider monkeys (Ateles chamek) maintain a relatively stable daily protein intake, but allow total energy intake to vary as a function of the composition of available food items. This is referred to as protein-dominated macronutrient balancing. Here we assess the influence of this nutritional strategy on daily and seasonal nutritional intakes, estimate the nutritional value of different foods, and interpret unusual food choices. We conducted continuous all-day observations of focal spider monkeys inhabiting a semideciduous forest in Bolivia. We recorded feeding events, collected foods, and analyzed their nutrient content. By using the Geometric Framework for nutrition, we show that individuals reached their daily end-point in nutrient space —balance between protein and nonprotein energy intake— by consuming nutritionally balanced foods or by alternating between nutritionally complementary foods. The macronutritionally balanced figs of Ficus boliviana were their primary staple food and therefore dominated their overall nutritional intake. Our results also demonstrate that spider monkeys consumed a diverse array of ripe fruits to overcome periods of fig scarcity rather than vice versa; they could obtain sufficient protein on a diet of pure fruit; and unripe figs constituted a nutritionally rewarding and reliable food resource. We hope that the approaches taken and the conclusions reached in this study will catalyze further inquiries into the nutritional ecology of frugivorous primates.     

New insights in insect prey choice by chimpanzees and gorillas in southeast Cameroon: the role of nutritional value

The insect diet of chimpanzees and gorillas living at the northern periphery of the Dja Biosphere Reserve in southeast Cameroon and its nutritional contribution is described. We analyzed fecal samples and recorded additional evidence of insectivory. A detailed prey species list is presented for both apes. We carried out nutritional analyses (macronutrients, macro- and micro-minerals) on 11 important and eight nonimportant, but accessible, ant and termite prey species, and estimated the average nutrient intake/day through insects. Although gorillas ate insects more frequently, the average prey biomass intake/day by chimpanzees was twice that by gorillas. The lack of tool-use by gorillas cannot be the main reason for the small overlap of important prey species. Both apes did not seem to consume ant prey for one or more specific nutrients. Also other factors, such as medicinal use, should be considered. Termites, on the other hand, seemed to be selected for particular nutrients. Gorilla intake of the important termite prey, Cubitermes and Thoracotermes, met with estimated iron requirements. Their potential role as antidiarrheal treatment is as yet unclear. Chimpanzee intake of the important termite prey, Macrotermes spp., met with estimated manganese requirements and the protein intake/day (mean: 2 g/d) reached significant values (>20 g/d). To fully understand the importance of nutritional contributions of insects to ape diets in Cameroon, the chemical composition and nutrient intake of fruit and foliage in their diets should be investigated.     

Digestive responses of two omnivorous rodents (<Emphasis Type="Italic">Peromyscus maniculatus</Emphasis> and <Emphasis Type="Italic">P. alstoni</Emphasis>) feeding on epigeous fungus (<Emphasis Type="Italic">Russula occidentalis</Emphasis>)

The sporocarps of hypogeous and epigeous fungi are important dietary items for forest dwelling rodents in temperate and tropical forests throughout the world. However, results of some pioneering works have demonstrated that fungi cannot be considered as nutritionally high-quality food items for some mycophagous small rodents. According to these studies, when mycophagous rodents feed on fungus, they showed a minimal digestibility, but whether this applies to most rodent species that include fungi in their diets is unknown. In this study, we experimentally evaluated body mass changes and feed preferences in captive deer (Peromyscus maniculatus) and volcano (P. alstoni) mice when fed on epigeous fungus (Russula occidentalis). In experiment 1, the animals were fed with fungus as the only feedstuff in comparison to regular rodent chow and oat. In experiment 2, the animals were fed with fungus in a free-choice arrangement together with equal amounts of rodent chow and oat. Both species lost ∼15% of their body mass within 4 days when fed on fungus alone, but gained 5–10% body mass during the same time period when ingesting oat and rodent chow, respectively, as the only feedstuff. However, in contrast, in the free-choice arrangement with all three feedstuffs, both species gained 20–30% body mass, and showed the highest feed preference for fungus followed by oat and rodent chow. In addition, apparent digestibility of energy and nitrogen were analyzed in both rodent species, which were 50–60% for fungus, whereas approximately 90–94% for rodent chow and oat. According to our results, animals need to supplement their diets with alternative high-quality food items in order to maintain and increase their body mass, suggesting that epigeous fungi are only of moderate nutritional value for small rodents. Futures studies should focus on exploring the importance of a mixture of fungal species in the diet of small mycophagous rodents.     

Intake and digestion of horned guan Oreophasis derbianus diets measured in three Mexican zoos

We conducted nutritional analyses of diets offered to and ingested by seven pairs of horned guans (Oreophasis derbianus) in three zoos. Digestibility was calculated with individually housed birds (n=1 at each zoo). Diets offered varied widely among institutions, both in ingredients fed as well as in nutrient composition. Feeding selectivity was evident through differences in composition of diets offered vs. consumed, with fruit (bananas, grape, and/or plantain) and avocado (when offered) highly preferred; green leaves, poultry pellets, and other vegetables comprised lesser proportions of the diet. All facilities fed 2–3X more food than consumed, allowing a great degree of choice of preferred items and potentially consumption of nutritionally imbalanced diets—in particular, mineral constituents. Diets were highly digestible; dry matter (DM) digestion coefficients ranged from 70 to ∼90%; protein digestibility varied from 30 to 80%; fat was >90% digestible. Diet composition was compared with known nutritional requirements of domestic avian species, and feeding recommendations discussed. Despite the wide variability in nutrient composition of diets eaten (i.e. protein 6–10% of DM; fat 2–17% of DM), no overt health problems were noted and all pairs had successfully reproduced on these diets. It is suggested that horned guans may have nutrient requirements more similar to those suggested for other frugivorous birds than values determined for poultry as the physiologic model. Comparisons with native food items, as well as more detailed nutrient balance studies, may provide even better guidelines for captive management of this highly endangered species. Zoo Biol 28:319–330, 2009. © 2009 Wiley-Liss, Inc.