Body weight,energy metabolism,and time in the life of birds

The breeding of birds, both large and small, is affected by two specific factors: (1) hypometry of egg weight relative to female body weight and (2) seasonality of breeding, with the favorable period being limited and almost equal for birds of different body sizes. Dozens of published allometric formulas describing the dependence of energy parameters of eggs and nestlings at different growth stages and the energy cost of parental care on the body weight of parents, eggs, and nestlings, respectively, are reviewed. It is shown that birds, especially species with a large body weight, repeatedly change their metabolic parameters during ontogeny in order to shorten the period of breeding and growth. In most species, the energy costs of breeding in both sexes are approximately equal. Bringing food in the bill allows birds to supply nestlings with the amount of energy that is dozens of times greater than that expended for obtaining the food. In placental mammals, only females are involved in offspring development. Therefore, the growth rate of embryos and energy expenditures for milk feeding are limited by the metabolic potential of the mother. As a consequence, mammalian offspring grow ten times slower than bird nestlings, the body weights of females being equal.     

Body size in proboscideans, with notes on elephant metabolism

Mass estimates for a number of fossil proboscideans were computed using regression analyses on appendicular bones to body mass, for seven specimens of modern elephants, for which body masses had been recorded prior to death. The marked differences in physical proportions between extant Loxodonta and Elephas , implying substantial differences in body mass at any given shoulder height, were not present in their long bone parameters. Length and least circumferences proved to be the best parameters for prediction of body mass. Some extinct proboscideans, notably certain Mammuthus and Deinotherium , were much larger than extant elephants. Both the basal and the field metabolic rates of extant elephants are lower than predicted for a hypothetical mammal, in accordance with their body size and subsistence on low-quality foods. The feeding quantities often ascribed to extant wild elephants are exaggerated, and would in fact have sufficed to nourish much larger species.  © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 140 , 523–549.     

Body temperature regulation,energy metabolism,and foraging in light-seeking and shade-seeking robber flies

Summary Robber flies (Diptera: Asilidae) were studied in Panama from May through August. Of the 16 species examined, 5 perched and foraged in the sun and 11 perched and foraged in the shade. Thoracic body temperatures of light-seeking flies ranged from 35.2–40.6°C during foraging. Light-seeking flies regulated body temperature behaviorally by microhabitat selection and postural adjustments, and physiologically by transferring warmed haemolymph from the thorax to the cooler abdomen. Thoracic temperatures of shade-seeking flies passively followed ambient temperature in the shade and these flies did not thermoregulate. None of these robber flies warmed endothermically in the absence of flight. Resting oxygen consumption ( ) of both groups scaled with body mass to the 0.77 power. The factorial increment in resulting from hovering flight ranged from 12 to 56. The increased markedly with body temperature in light-seeking flies and probably explains the greater foraging effort observed in these species. Wing loading of all 16 species of robber flies scaled with body mass to the 0.39 power. Large light-seeking flies had heavier wing loading than large shade-seeking flies. The differences in body temperature and wing loading between light-seeking and shade-seeking robber flies may be related to differences in flight speed and maneuverability during foraging.     

Body size, mortality, and longevity

The body-size dependent relationships of mortality and longevity are examined for birds and eutherian mammals. Differences between mass exponents for maximum recorded longevity and survival times for fractions of original adult populations confirm the age-dependence of mortality in both classes and a size-dependency of population-age distribution. The potential number of offspring produced by a surviving fraction of a mammalian population appears to be a size-independent ecological constant. Social structure would be more likely in larger animals since greater continuity would be provided when a higher proportion of the population consisted of senior, experienced animals, as described by the ratio of time for survival of 1 in 1000 to maximum potential lifespan: t0.001/tmax = 0.91 m0.32/2.94 m0.20 = 0.31 m0.12, that is, the expected lifespan approaches the maximum as size increases.     

Body size and human energy requirements: reduced mass-specific resting energy expenditure in tall adults.

Two observations favor the presence of a lower mass-specific resting energy expenditure (REE/weight) in taller adult humans: an earlier report of height (H)-related differences in relative body composition; and a combined model based on Quetelet and Kleiber's classic equations suggesting that REE/weight proportional, variantH(-0.5). This study tested the hypothesis stating that mass-specific REE scales negatively to height with a secondary aim exploration of related associations between height, weight (W), surface area (SA), and REE. Two independent data sets (n = 344 and 884) were evaluated, both with REE measured by indirect calorimetry and the smaller of the two including fat estimates by dual-energy X-ray absorptiometry. Results support Quetelet's equation (W proportional, variantH(2)), but Kleiber's equation approached the interspecific mammal form (REE proportional, variantW(0.75)) only after adding adiposity measures to weight and age as REE predictors. REE/weight scaled as H( approximately (-0.5)) in support of the hypothesis with P values ranging from 0.17 to <0.001. REE and SA both scaled as H( approximately 1.5), and REE/SA was nonsignificantly correlated with height in all groups. These observations suggest that adiposity needs to be considered when evaluating the intraspecific scaling of REE to weight; that relative to their weight, taller subjects require a lower energy intake for replacing resting heat losses than shorter subjects; that fasting endurance, approximated as fat mass/REE, increases as H(0.5); and that thermal balance is maintained independent of stature by evident stable associations between resting heat production and capacity of external heat release. These observations have implications for the modeling of adult human energy requirements and associate with anthropological concepts founded on body size.     

Effects of meal size, clutch, and metabolism on the energy efficiencies of juvenile Burmese pythons, Python molurus

We explored meal size and clutch (i.e., genetic) effects on the relative proportion of ingested energy that is absorbed by the gut (apparent digestive efficiency), becomes available for metabolism and growth (apparent assimilation efficiency), and is used for growth (production efficiency) for juvenile Burmese pythons (Python molurus). Sibling pythons were fed rodent meals equaling 15%, 25%, and 35% of their body mass and individuals from five different clutches were fed rodent meals equaling 25% of their body mass. For each of 11–12 consecutive feeding trials, python body mass was recorded and feces and urate of each snake was collected, dried, and weighed. Energy contents of meals (mice and rats), feces, urate, and pythons were determined using bomb calorimetry. For siblings fed three different meal sizes, growth rate increased with larger meals, but there was no significant variation among the meal sizes for any of the calculated energy efficiencies. Among the three meal sizes, apparent digestive efficiency, apparent assimilation efficiency, and production efficiency averaged 91.0%, 84.7%, and 40.7%, respectively. In contrast, each of these energy efficiencies varied significantly among the five different clutches. Among these clutches production efficiency was negatively correlated with standard metabolic rate (SMR). Clutches containing individuals with low SMR were therefore able to allocate more of ingested energy into growth.     

Effects of meal size, clutch, and metabolism on the energy efficiencies of juvenile Burmese pythons, Python molurus.

We explored meal size and clutch (i.e., genetic) effects on the relative proportion of ingested energy that is absorbed by the gut (apparent digestive efficiency), becomes available for metabolism and growth (apparent assimilation efficiency), and is used for growth (production efficiency) for juvenile Burmese pythons (Python molurus). Sibling pythons were fed rodent meals equaling 15%, 25%, and 35% of their body mass and individuals from five different clutches were fed rodent meals equaling 25% of their body mass. For each of 11-12 consecutive feeding trials, python body mass was recorded and feces and urate of each snake was collected, dried, and weighed. Energy contents of meals (mice and rats), feces, urate, and pythons were determined using bomb calorimetry. For siblings fed three different meal sizes, growth rate increased with larger meals, but there was no significant variation among the meal sizes for any of the calculated energy efficiencies. Among the three meal sizes, apparent digestive efficiency, apparent assimilation efficiency, and production efficiency averaged 91.0%, 84.7%, and 40.7%, respectively. In contrast, each of these energy efficiencies varied significantly among the five different clutches. Among these clutches production efficiency was negatively correlated with standard metabolic rate (SMR). Clutches containing individuals with low SMR were therefore able to allocate more of ingested energy into growth.     

Body size, biomic specialization and range size of African large mammals

Aim The goal of this paper is to examine the relationships between body size, biomic specialization and range size in the African large mammals, which are defined as all the African species corresponding to the orders Primates, Carnivora, Proboscidea, Perissodactyla, Hyracoidea, Tubulidentata, Artiodactyla and Pholidota. Location The study used the large mammal assemblage from Africa. Methods The degree of biomic specialization of African large mammals is investigated using the biomic specialization index (BSI) for each mammal species, based on the number of biomes it inhabits. Range size for each species is measured as the latitudinal extent of the geographical distribution of the species. We have analysed our data using both conventional cross‐species analyses and phylogenetically independent contrasts. Results There is a polygonal relationship between species biomic specialization and body size. While small and large species are biomic specialists, medium‐sized species are distributed along the whole range of biomic specialization. The latitudinal extent–body size relationship is approximately triangular. Small‐bodied species may have either large or small ranges, whereas large‐bodied ones have only large ranges. A positive correlation between latitudinal extent and biomic specialization is evident, although their relationship is better described as triangular. Main conclusions We found a polygonal relationship between species biomic specialization and body size, which agrees with previous arguments that small‐bodied species have more limited dispersal and, therefore, they may come to occupy a lesser proportion of their potential inhabitable biomes. On the other hand, large‐bodied species are constrained to inhabit biomes with a high productivity. A polygonal relationship between species latitudinal extent and body size in African large mammals agrees with previous studies of the relationship between range size and body size in other continents. The independent study of the macroecological pattern in biomic specialization highlights different factors that influence the body size–range size relationship. Although body size is usually implicated as a correlate of both specialization and geographical range size in large mammals, much of the variation in these variables cannot be attributed to size differences but to biome specific factors such as productivity, area, history, etc.     

Bone remodeling, energy metabolism, and the molecular clock

The adult skeleton is constantly renewed through bone remodeling. Four recent papers (Baldock et al., 2007; Lee et al., 2007; Lundberg et al., 2007; Sato et al., 2007) provide new insights into central and peripheral control of this remodeling sequence. Two of the studies add to our knowledge of the complex hypothalamic modulation of bone turnover mediated by NMU and NPY via the sympathetic nervous system, while the other two focus on the peripheral neural target, the osteoblast, and its regulation by neuropeptides and osteocalcin. These findings support a new paradigm concerning the regulation of bone remodeling and provide a foundation for novel approaches to preventing osteoporosis.     

Scaling of home range size: Body size, metabolic needs and ecology

It is hardly surprising that elephants range over larger areas than rabbits. We expect larger animals to need to cover more ground to obtain their food. Equally, we expect herbivores to require less area over which to forage than carnivores of the same size. It might be thought that home range areas, or the sizes of feeding territories, would vary with body size and ecology in a straightforward manner. In fact we still do not know the precise reasons why animals have the home range sizes that they do.     

Body size, competitive interactions, and the local distribution of Triturus newts

1. Pairs of European Triturus newt species of similar size tend not to co-occur syntopically, suggesting that similarity in body size is associated with competitive interactions that prevent coexistence. I tested this hypothesis with an experiment involving larvae of four species in 675-L artificial ponds. 2. There were strong interactions between most species pairs. Even the small T. helveticus had a clear impact on the larger T. alpestris. Pairs of species with different body sizes did not interact less strongly. 3. A standard increase in competitor biomass (c. 2 g mass at metamorphosis) caused 42% lower expected survival from hatching to 1 year of age, regardless of whether the species were of similar or different size. In most cases this resulted from delayed metamorphosis, reduced size at emergence, and slightly lower larval survival. 4. A standard increase in competitor density (0.74 individuals m(-2)) caused a greater reduction in expected 1-year survival when the competitor was larger (18% decline) than when both species were of similar size (6% decline), primarily because the very large T. cristatus consumed the smallest species. 5. These findings suggest that species interactions during the larval stage cannot explain distribution patterns of same- and different-sized Triturus.     

Body size, age and reproduction in the Smooth newt, Triturus vulgaris

Data on the relationships between individual body size, age and reproduction were obtained for a sample of Smooth newts collected from several sites in southern England. Age was determined by counting lines of arrested growth in histological sections of humerus. In males and females, body size increases with age, but only in the former sex is the correlation statistically significant. In both sexes, there is great inter-individual variability in body size within a year class. Measures of fecundity (testis size, ovary size, clutch size and oocyte size) are positively correlated with body size, but not age. The timing of first reproduction does not seem to depend on the attainment of a fixed body size; the earliest age at first reproduction is two or three years. Together with information obtained during previous studies, the data we present support the hypothesis that the Smooth newt may be an r -selected, colonizing species.     

Body size, age and reproduction in the leopard toad, Bufo pardalis

Data on the relationships between body size and age were obtained for a sample of leopard toads Bufo pardalis from a breeding population of this species from the Cape Peninsula, South Africa. Age was determined by counting the number of lines of arrested growth in histological sections of a digit clipped from each individual. In males there was a positive, but weak, correlation (explaining only 18% of the variance) between body size and age, and in females no correlation at all existed between these two variables. Males which were successful in obtaining matings were not older than unsuccessful males. Age of males at the breeding site ranged from one to three years, whereas females ranged from two to six years old. This represents both the earliest age of reproduction, as well as the greatest difference in longevity between the sexes, documented for an anuran species.