Nutritional geometry and macronutrient variation in the diets of gannets: the challenges in marine field studies

Tait, Alice H.; Raubenheimer, David; Stockin, Karen A.; Merriman, Monika; Machovsky‐Capuska, Gabriel E.

doi:10.1007/s00227-014-2544-1

Cited by 42 publications

(59 citation statements)

References 52 publications

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“…For example, the average log ratio of protein to lipid in garfish was 29.7 % higher in 2015 than in 2014. These results support previous findings in this species (Tait et al 2014) and also emphasize the nutritional variability of prey consumed by marine predators (Wanless et al 2005;Spitz et al 2010;Lenky et al 2012), and draws into question the long-term assumption that wild predators feed on prey that are similar in their nutritional composition (Westoby 1978;Stephens and Krebs 1986;Galef 1996).…”

Section: Foraging In a Complex Marine Nutritional Environmentsupporting

confidence: 85%

“…Despite such temporal variation, the gannet colony at FS has shown continuous growth (Schuckard et al 2012). Our findings may thus be seen as further evidence of this species' ability to successfully adjust to nutritional fluctuations of prey (Grémillet et al 2008;Tait et al 2014). In addition, during the three breeding seasons, adult chickrearing Australasian gannets consistently composed around 80 % of their diet from three different types of prey.…”

Section: Foraging In a Complex Marine Nutritional Environmentmentioning

confidence: 79%

“…Following Tait et al (2014), undigested samples of the main prey species found in the diets of Australasian gannets were selected for proximate composition analyses. Prior to analysis, each sample was partially thawed and weighed to within 0.1 g, dried overnight in a convection oven at 60 °C and ground to powder with a laboratory mill.…”

Section: Macronutrient Composition Of Preymentioning

confidence: 99%

“…First, foods are complex mixtures of many nutrients parcelled at differing ratios, and each nutrient has its 75 Page 2 of 14 own functional implications for the forager . In addition, the nutritional composition of foods varies geographically (Tait et al 2014;Rothman et al 2015). Second, within populations optimal nutrient intake can be variable, for example where nutrient requirements are sex-or age specific Senior et al 2015).…”

Section: Introductionmentioning

confidence: 98%

“…Gannets are carnivorous central place foragers , 2014a, and a developing model species for testing field-based nutritional ecology questions (Tait et al 2014). Here we combined the use of dietary analysis, proximate composition and nutritional geometry (right-angled mixture triangle nutritional models-RMT) to examine the macronutrient preferences of Australasian gannets at Farewell Spit gannetry (FS) in New Zealand.…”

Section: Introductionmentioning

confidence: 99%

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Sex-specific macronutrient foraging strategies in a highly successful marine predator: the Australasian gannet

et al. 2016

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Farewell Spit gannetry in New Zealand. Our results showed intra-and inter-specific variation in the protein, lipid and water composition of prey captured by our sample of 111 Australasian gannets. In addition, we observed significant differences in the Australasian gannets' nutritional niche between seasons. We provide evidence of sex-specific macronutrient foraging strategies in a successful marine predator in the wild. We have shown that in spite of fluctuations in the nutritional composition of foods available to Australasian gannets, males consistently capture prey with higher protein-to-lipid ratios and lower lipid-to-water ratios than females. These results aid to better understand the evolutionary relationship between macronutrient selection and sex-specific traits in wild animals. They also suggest an incentive for these predators to combine individually imbalanced but nutritionally complementary foods to achieve dietary balance, further highlighting the likelihood that prey selection is guided by the balance of macronutrients, rather than energy alone.

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Section: Foraging In a Complex Marine Nutritional Environmentsupporting

confidence: 85%

Section: Foraging In a Complex Marine Nutritional Environmentmentioning

confidence: 79%

Section: Macronutrient Composition Of Preymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Sex-specific macronutrient foraging strategies in a highly successful marine predator: the Australasian gannet

et al. 2016

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Dietary protein supplementation and its consequences for intake, digestion, and physical activity of a carnivorous marsupial, Sminthopsis crassicaudata

Yuan

Wilder

Raubenheimer

et al. 2018

Ecology and Evolution

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Diet regulation behavior can mediate the consequences of imbalanced diets for animal well‐being, particularly for captive species that have little dietary choice. Dasyurids (carnivorous marsupials) are of conservation concern in Australia, and many species are in captive breeding programmes. However, their nutrient targets and dietary regulation behaviors are poorly understood, a limitation that may decrease the breeding success and well‐being of captive animals. We tested how dietary protein content influenced the intake and utilization of nutrients, physical activity, and body mass of fat‐tailed dunnarts Sminthopsis crassicaudata. Twelve adult dunnarts from six sibling pairs (one female and one male per pair) were provided ad libitum access to three diets in a repeated measures design: cat food, cat food supplemented with raw lean beef (1:1), and cat food supplemented with cooked lean beef (1:1). Food intake, activity level, and fecal output were measured daily. Dunnarts significantly decreased food intake, increased protein digestion, and physical activity, but body mass was unchanged when on the high‐protein diet compared to the normal cat food diet. These observations suggest a capacity of dunnarts to maintain constant body mass using a dynamic balance of feeding, digestion, and activity. We also found a significant effect of family, with differences between families as large as the difference between the diet treatments, suggesting a genetic component to diet selection. The nutrient regulation responses of dunnarts to high‐protein diets and the strong family effects provide important messages for the management of populations of small carnivores, including the aspects of dietary manipulation and conservation of genetic diversity.

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Functional macronutritional generalism in a large omnivore, the brown bear

Coogan

Raubenheimer

Stenhouse

et al. 2018

Ecology and Evolution

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We combine a recently developed framework for describing dietary generalism with compositional data analysis to examine patterns of omnivory in a large widely distributed mammal. Using the brown bear (Ursus arctos) as a model species, we collected and analyzed data from the literature to estimate the proportions of macronutrients (protein, carbohydrate, and lipid) in the diets of bear populations. Across their range, bears consumed a diversity of foods that resulted in annual population diets that varied in macronutrient proportions, suggesting a wide fundamental macronutrient niche. The variance matrix of pairwise macronutrient log‐ratios indicated that the most variable macronutrient among diets was carbohydrate, while protein and lipid were more proportional or codependent (i.e., relatively more constant log‐ratios). Populations that consumed anthropogenic foods, such agricultural crops and supplementary feed (e.g., corn), had a higher geometric mean proportion of carbohydrate, and lower proportion of protein, in annual diets. Seasonally, mean diets were lower in protein and higher in carbohydrate, during autumn compared to spring. Populations with anthropogenic subsidies, however, had higher mean proportions of carbohydrate and lower protein, across seasons compared to populations with natural diets. Proportions of macronutrients similar to those selected in experiments by captive brown bears, and which optimized primarily fat mass gain, were observed among hyperphagic prehibernation autumn diets. However, the majority of these were from populations consuming anthropogenic foods, while diets of natural populations were more variable and typically higher in protein. Some anthropogenic diets were close to the proportions selected by captive bears during summer. Our results suggest that omnivory in brown bears is a functional adaptation enabling them to occupy a diverse range of habitats and tolerate variation in the nutritional composition and availability of food resources. Furthermore, we show that populations consuming human‐sourced foods have different dietary macronutrient proportions relative to populations with natural diets.

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Nutritional geometry and macronutrient variation in the diets of gannets: the challenges in marine field studies

Cited by 42 publications

References 52 publications

Sex-specific macronutrient foraging strategies in a highly successful marine predator: the Australasian gannet

Sex-specific macronutrient foraging strategies in a highly successful marine predator: the Australasian gannet

Dietary protein supplementation and its consequences for intake, digestion, and physical activity of a carnivorous marsupial, Sminthopsis crassicaudata

Functional macronutritional generalism in a large omnivore, the brown bear

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