Mean Body Mass (mean + body_mass)

Distribution by Scientific Domains

Terms modified by Mean Body Mass

  • mean body mass index

  • Selected Abstracts

    Estimating fat and protein fuel from fat and muscle scores in passerines

    IBIS, Issue 4 2009
    Fat is the prime energy source for birds during prolonged exercise, but protein is also catabolized. Estimates of the amount of catabolizable fat and protein (termed fat and protein fuel) are therefore important for studying energetics of birds. As fat and protein fuel can only be measured by sacrificing individuals or by use of technically complex methods, scoring systems were invented to estimate fat and protein fuel of birds in the field. The visible subcutaneous fat deposits and the thickness of the flight muscles are each scored on an ordinal scale but these scales do not correspond linearly to fat and protein fuel within species, which is needed for analyses such as flight range estimates. We developed an anova -type model to estimate fat and protein fuel from fat scores (FS) and muscle scores (MS) along with total mass and a size measurement. Using data from 11 337 individuals of eight passerine species (Common Nightingale Luscinia megarhynchos, Eurasian Reed Warbler Acrocephalus scirpaceus, Melodious Warbler Hippolais polyglotta, Willow Warbler Phylloscopus trochilus, Orphean Warbler Sylvia hortensis, Garden Warbler Sylvia borin, Common Whitethroat Sylvia communis, Subalpine Warbler Sylvia cantillans) mist-netted in Mauritania, West Africa, we tested for independence of FS and MS and for variation in the relationship between scores and associated mass in response to physiological state. FS, MS and third primary length (size) explained variation in body mass of all eight species analysed (R2: 0.56,0.77). The parameter estimates of the model showed that fat and protein fuel increased monotonically with increasing fat and muscle scores. In two species we found small differences in the estimates between physiological states (seasons). We evaluated our model by comparing the predicted body mass of birds with both FS and MS equal to 0 with the mean body mass of individuals mist-netted with both scores equal to zero. The values were very close. The amount of fat extracted from dead Garden and Willow Warblers was within the range of predicted fat fuel derived from the model. We conclude that our model is a useful non-invasive method to estimate simultaneously mean fat and protein fuel of small passerines and we provide recommendations on its use. [source]

    Effects of food limitation and emigration on self-thinning in experimental minnow cohorts

    J. B. Dunham
    Summary 1.,The theory of food-regulated self-thinning (FST) for mobile animals predicts population density (N) to be an inverse function of mean body mass (W) scaled to an exponent (b), such that N = k W,b, where k is a constant. FST also predicts energy requirements (or energy flow) to remain constant over time (termed energetic equivalence) as losses to cohorts (e.g. emigration and mortality) are balanced by increased growth of surviving individuals. 2.,To test these predictions, we analysed the dynamics of six experimental minnow cohorts. Replicate populations of fish were held under identical conditions with a constant and limited supply of food over a 126-day period. Half of the cohorts were open to emigration, and half were closed so that fish could only be lost through starvation mortality. 3.,Patterns of self-thinning indicated non-linear changes in population density and energy flow in relation to changes in mean body mass and time, respectively. Non-linear patterns of self-thinning were probably due to a delayed growth response to changes in population density effected through mortality and/or emigration. Contrary to results of similar experiments on other fish, emigration did not have a significant influence on the pattern of self-thinning. 4.,These results may be attributed to trophic interactions within cohorts and the importance of social behaviour to cohort dynamics. Both population density and energy flow in our experimental populations appeared to cycle, with episodes of starvation and mortality alternating with food recovery and weight gain, as predicted by recent models of stepwise die-off and stunted growth in animal cohorts. 5.,Most of the support for FST in mobile animals comes from observational data on mean body mass and population density. Potentially important mechanisms, including the manner in which individuals are lost or retained in populations, are usually not investigated directly. Such tests of FST can only provide equivocal support. Detailed observational study and controlled experiments are needed to understand casual mechanisms. [source]

    Reproduction of the raccoon dog (Nyctereutes procyonoides) after feeding or food deprivation in winter

    J. Asikainen
    Summary The wild raccoon dog (Nyctereutes procyonoides, Canidae, Carnivora) goes through autumn fattening followed by winter sleep. Farmed raccoon dogs also exhibit autumn fattening but not winter sleep, as a result of daily feeding and lack of nests. We studied the effects of food deprivation and winter sleep or active winter feeding on the physiology and reproduction of farm-born raccoon dogs. Eighty-six animals were put on a 2-month fast in November,December. The fast caused no deleterious effects on the health of the raccoon dogs. In the spring the food-deprived animals had slightly more cubs per mated female than the fed animals. There was a significant negative correlation between the number of cubs obtained and the mean body mass of the females at the beginning of the mating season. The highest mean number of cubs was obtained by the females that weighed 5,7 kg. The results indicate that the raccoon dog is finely adapted to a long period of food deprivation in the winter. Furthermore, winter sleep and food deprivation could be introduced to farm conditions by providing the raccoon dogs with nestboxes and withholding food for a period of 6,8 weeks in mid-winter. [source]

    Primary productivity can affect mammalian body size frequency distributions

    OIKOS, Issue 2 2001
    Birgitta Aava
    Frequency distributions of mammal body sizes in large-scale assemblages have often been found to show a positive skew. In an attempt to explain this pattern, a model has been put forward which incorporates energetic constraints on fitness and thereby predicts optimal body sizes corresponding to the mode of the distribution. A key assumption of the model is that energy is unlimited. However, if energy is limited, the input of energy into a herbivorous mammal community should influence the shape of the frequency distribution. Thus, I propose that increases in primary productivity will decrease the variation of body size and increase the mean body size in a distribution. So, in low-productivity environments we should see a predominance of small-sized species, but with a great variation of body sizes due to limitations of resources (energy). I tested this hypothesis using the herbivorous mammal fauna (rodents, bats and marsupials) in seven biomes of Australia. Because herbivorous marsupials generally are fairly large-bodied while rodents and bats are small-sized and because marsupials also have a different mode of reproduction from placental mammals, the hypothesis was also tested on placental mammals and marsupials separately. There was no clear mode for the entire assemblage in any biome, but as primary productivity increased, the variation of body masses decreased and the mean body mass of the distribution increased. Body mass distributions of both placental mammals and marsupials displayed clear modes. Placental mammals also showed an increase in mean body mass. The variation in body mass of marsupials was highest for the intermediately productive biomes. Primary productivity does seem to have some effect on mammalian body mass in this case, but the results here need to be complemented with studies of other assemblages before any general conclusions can be drawn. It is also important to distinguish which taxa are affected in a heterogeneous assemblage like the Australian herbivorous mammal fauna. [source]

    Lack of discontinuous gas exchange in a tracheate arthropod, Leiobunum townsendi (Arachnida, Opiliones)

    John R. B. Lighton
    Abstract The discontinuous gas exchange cycle, characterized by stringent spiracular control and periods of near-zero external CO2 emission separated by ,bursts' of CO2 emission, has evolved independently in several taxa of tracheate arthropods. These include the hexapoda, diplopoda, and several arachnid taxa; ticks, pseudoscorpions and solphugids. This paper presents the first data on gas exchange kinetics in a harvestman (Arachnida; Opiliones). The experimental animal, Leiobunum townsendi Weed, from an arid area of the south-western United States, displayed a metabolic rate similar to those of other arthropods at 25 °C (129 ± 22 µW). Their CO2 emission kinetics showed, when the animals were motionless, only minor variations about a mean value of 0.0217 ± 0.0037 mL/h (n = 6, mean body mass 86 mg). Expressed on an intra-recording basis, the coefficient of variation of CO2 emission (= SD/MEAN), which is an index of short-term gas emission fluctuations and thus of spiracular control, had a mean value of only 0.082. In contrast, the coefficient of variation of animals employing a discontinuous gas exchange cycle is >,1.5. Gas exchange in opilionids, unlike the case with most other tracheate arthropods, may therefore be dominated by simple diffusion without a prominent role for wide modulations of spiracular conductance. Contributory to this conservative spiracular control strategy may be the weak degree of tracheation in opilionids, combined with circulating haemocyanin, which acts as both a transport medium and a buffering reservoir for respiratory gas exchange. [source]

    Cultural consonance and body morphology: Estimates with longitudinal data from an Amazonian society

    Victoria Reyes-García
    Abstract Researchers have hypothesized that the degree to which an individual's actual behavior approximates the culturally valued lifestyle encoded in the dominant cultural model has consequences for physical and mental health. We contribute to this line of research by analyzing data from a longitudinal study composed of five annual surveys (2002,2006 inclusive) from 791 adults in one society of foragers,farmers in the Bolivian Amazon, the Tsimane'. We estimate the association between a standard measure of individual achievement of the cultural model, cultural consonance, and three indicators of body morphology. Drawing on research suggesting that in societies in the early stages of economic development an increase in socioeconomic status is associated with an increase in mean body mass, we expect to find a positive association between cultural consonance and three anthropometric measures. We found the expected positive association between cultural consonance and anthropometric measures,especially for men,only when using ordinary least square (OLS) regression models, but not when using fixed-effects regression models. The real magnitude of the association was low. The comparison of estimates from OLS and fixed-effect regression models suggests that previous findings on the effects of cultural consonance on body morphology using cross-sectional data should be read with caution because the association might be largely explained by fixed characteristics of individuals not accounted in OLS models. Am J Phys Anthropol 143:167,174, 2010. © 2010 Wiley-Liss, Inc. [source]

    Variability and size in mammals and birds

    Body size, its variability, and their ecological correlates have long been important topics in evolutionary biology. Yet, the question of whether there is a general relationship between size and size-relative variability has not previously been addressed. Through an analysis of body-mass and length measurements from 65 074 individuals from 351 mammalian species, we show that size-relative variability increases significantly with mean species body size. Analysis of mean body mass and standard deviations for 237 species of birds revealed the same pattern. We present three plausible alternatives explanations and eliminate several others. Of these, the hypothesis that the increase in size-relative variability with mean body mass is related to the scaling of body mass components is most strongly supported. In effect, larger mammals and birds are more variable because their body mass is composed to greater relative degree of components with higher intrinsic variability (bone, fat, and muscle). In contrast, smaller mammals and birds have lower body mass variability because they are composed to a greater relative extent of components (viscera and nervous system) in which size variation is more highly constrained by energetic and functional factors. [source]

    A shortening of the manus precedes the attenuation of other wing-bone elements in the evolution of flightlessness in birds

    ACTA ZOOLOGICA, Issue 1 2010
    R. L. Nudds
    Abstract Nudds, R. L. and Slove Davidson, J. 2010. A shortening of the manus precedes the attenuation of other wing-bone elements in the evolution of flightlessness in birds. ,Acta Zoologica (Stockholm) 91: 115,122 This is the first study to present evidence for a general pattern of wing-bone attenuation during the early stages of the evolution of flightlessness. A comparative analysis using phylogenetic independent contrasts showed that in families that contain both flighted (volant) and flightless species, the volant species have shorter wings and total-arm (humerus + ulna + manus) lengths relative to their body masses than the species within their wholly volant sister families. A shortening of the manus may typify the early stages of the evolution of flightlessness, with the humerus and ulna attenuating later, perhaps because of their role in maintaining the position of the aerodynamically important alula. A shorter wing relative to body mass was not the result of the inverse (i.e. heavier body mass relative to wing length) because mean body masses of volant members of flightless families were similar to or lower than those of their wholly volant sister families. Despite finding a common trend in the wing morphologies of volant members of flightless families, it seems unlikely that a general model of selection pressures driving the evolution of flightlessness exists. At the very least, a dichotomy between those birds that have lost the ability to fly in order to gain the ability to swim and terrestrial forms, may persist. [source]

    Partitioning phylogenetic and adaptive components of the geographical body-size pattern of New World birds

    GLOBAL ECOLOGY, Issue 1 2008
    Lizabeth Ramirez
    ABSTRACT Aim To evaluate seasonal body-size patterns for New World birds in geographical space, to develop environmental models to explain the gradients, and to estimate phylogenetic and adaptive contributions. Location The Western Hemisphere. Methods We used range maps to generate gridded geometric mean body masses. Summer and winter patterns were distinguished based on breeding and non-breeding ranges. We first generated the geographical gradients, followed by phylogenetic eigenvector regression to generate body sizes predicted by the birds' positions in a phylogenetic tree, which were used to generate the expected phylogenetic gradient. Subtracting the expected pattern from the observed pattern isolated the adaptive component. Ordinary least squares multiple-regression models examined factors influencing the phylogenetic, adaptive and combined components of the seasonal body-size patterns, and non-spatial and spatial models were compared. Results Birds are larger in the temperate zones than in the tropics. The gradient is quantitatively stronger in winter than in summer. Regression models explained 66.6% of the variance in summer mass and 45.9% of the variance in winter mass. In summer, phylogenetic and adaptive responses of birds contribute equally to the gradient. In winter, the gradient in North America is much stronger than that expected by taxonomic turnover, and responses of species independent of their family membership drive the overall pattern. Main conclusions We confirm Bergmann's rule in New World birds and conclude that winter temperatures ultimately drive the pattern, exerting selection pressures on birds that overwhelm patterns expected by phylogenetic inertia at the family level. However, in summer, the movement of migratory species into the temperate zone weakens the gradient and generates a pattern more congruent with that expected from the taxonomic composition of the fauna. The analytical method we develop here represents a useful tool for partitioning the phylogenetic and non-phylogenetic components of spatially explicit macroecological data. [source]