Commuting fruit bats beneficially modulate their flight in relation to wind

When animals move, their tracks may be strongly influenced by the motion of air or water, and this may affect the speed, energetics and prospects of the journey. Flying organisms, such as bats, may thus benefit from modifying their flight in response to the wind vector. Yet, practical difficulties have so far limited the understanding of this response for free-ranging bats. We tracked nine straw-coloured fruit bats (Eidolon helvum) that flew 42.5 ± 17.5 km (mean ± s.d.) to and from their roost near Accra, Ghana. Following detailed atmospheric simulations, we found that bats compensated for wind drift, as predicted under constant winds, and decreased their airspeed in response to tailwind assistance such that their groundspeed remained nearly constant. In addition, bats increased their airspeed with increasing crosswind speed. Overall, bats modulated their airspeed in relation to wind speed at different wind directions in a manner predicted by a two-dimensional optimal movement model. We conclude that sophisticated behavioural mechanisms to minimize the cost of transport under various wind conditions have evolved in bats. The bats’ response to the wind is similar to that reported for migratory birds and insects, suggesting convergent evolution of flight behaviours in volant organisms.     

Predicted impact of climate change on European bats in relation to their biogeographic patterns

There has been considerable recent interest concerning the impact of climate change on a wide range of taxa. However, little is known about how the biogeographic affinities of taxa may affect their responses to these impacts. Our main aim was to study how predicted climate change will affect the distribution of 28 European bat species grouped by their biogeographic patterns as determined by a spatial Principal Component Analysis. Using presence‐only modelling techniques and climatic data (minimum temperature, average temperature, precipitation, humidity and daily temperature range) for four different climate change scenarios (IPCC scenarios ranging from the most extreme A1FI, A2, B2 to the least severe, B1), we predict the potential geographic distribution of bat species in Europe grouped according to their biogeographic patterns for the years 2020–2030, 2050–2060 and 2090–2100. Biogeographic patterns exert a great influence on a species' response to climate change. Bat species more associated with colder climates, hence northern latitudes, could be more severely affected with some extinctions predicted by the end of the century. The Mediterranean and Temperate groups seem to be more tolerant of temperature increases, however, their projections varied considerably under different climate change scenarios. Scenario A1FI was clearly the most detrimental for European bat diversity, with several extinctions and declines in occupied area predicted for several species. The B scenarios were less damaging and even predicted that some species could increase their geographical ranges. However, all models only took into account climatic envelopes whereas available habitat and species interactions will also probably play an important role in delimiting future distribution patterns. The models may therefore generate ‘best case’ predictions about future changes in the distribution of European bats.     

Coastal plain halophytes and their relation to soil ionic composition

Halophytic coastal communities in Bahia Blanca, Argentina, were examined in relation to soil salinity along a transect from inland to the sea. The relationships between soil electrical conductivity and dominance-abundance values for different species were determined. The Chañaral community with its most conspicuous species Geoffroea decorticans was present in soils with the lowest salinity levels in the area. Halophytic underbush develops at soil salinity values of intermediate soil electrical conductivity, the characteristic species being Cyclolepis genistoides, Atriplex undulata and Salicornia ambigua. Halophytic shrub-like steppe vegetation, dominated by Allenrolfea patagonica or Heterostachys ritteriana, is present in soils with high salinity. It is concluded that the ionic composition of plants was a stable characteristic for different species and did not vary with changes in soil salinity.     

Lipid composition of cultured human keratinocytes in relation to their differentiation

The present study was undertaken to explore the possibility of the use of cultured human keratinocytes for the study of changes in lipid composition in relation to epidermal differentiation. In a submerged culture system, in which the stratification is incomplete, no significant differences have been found between the lipid composition of cells grown either at low calcium concentration (0.06 mM) (at which the keratinocyte differentiation is markedly retarded) or at normal calcium concentration (1.6 mM) (at which some differentiation takes place). Under these conditions the amount of phospholipids and sterols was high and that of ceramides was low. Furthermore, the acylglucosylceramides (AGC) and acylceramides (AC), the latter one known to be involved in water barrier function, were found to be absent. Contrary to this, both AGC and AC were found to be present in significant amounts in an air-exposed model using de-epidermized dermis (DED) as a substrate (in which, as judged from morphologic criteria, the extent of keratinocyte stratification is similar to that seen under the in vivo conditions). Fatty acid analysis revealed significantly lower content of 18:2 and higher content of 16:1 and 18:1 acids with all culture conditions used, as compared to the parent epidermis. This is probably a result of fatty acid levels and composition in fetal calf serum (which was used in the present study) that differ markedly from the in vivo situation. The 20:4 content was similar to that in the epidermis only in cells cultured under the submerged conditions, during which they have been found (Isseroff et al. 1987. J. Lipid Res. 28: 1342-1349) to be able to convert 18:2 to 20:4. In DED cultures, however, the 20:4 content was markedly lower. Under all culture conditions used, the triglyceride content was higher as compared to the non-cultured epidermis. The high content of triglycerides and the fatty acid composition of the various lipid fractions showed a resemblance with what is found in the epidermis in essential fatty acid-deficient animals. This resemblance was confirmed by electron micrographs which revealed the presence of some partially or completely empty lamellar bodies. The results of the present study suggest that the air-exposed culture model, in which the keratinocytes show a high extent of stratification, could be of great value in the study of epidermal lipid metabolism. However, further alterations in culture conditions are necessary to more closely approximate the lipid composition of noncultured epidermis.     

Optimization and characterization of walnut beverage emulsions in relation to their composition and structure

A central composite rotatable design (CCRD) was used to evaluate the effects of walnut oil (WO, 3-6%, w/w) and gum arabic (GA, 5-10%, w/w) on the average droplet size (D(32)), specific surface area (SSA), polydispersity index (span), apparent viscosity, interfacial tension and opacity of walnut-beverage emulsions. The response surface methodology (RSM) showed that the significant second-order polynomial regression equations with high R(2) (>0.95) were successfully fitted for all responses as function of independent variables. The linear effect of WO had a significant term in all reduced models. The overall optimum region was found to be at the combined level of 10% (w/w) GA content and 5.84% (w/w) WO concentration. At this optimum point, D(32), SSA, span, apparent viscosity, interfacial tension and opacity of emulsions were 0.609 μm, 8.236 m(2)/ml, 0.886, 1.336 Pa s, 51.37 mN/m and 0.810, respectively. No significant (p>0.05) difference was found between the actual values and predicted values. Moreover, principal component analysis (PCA), conducted via PCA variable loadings and cluster dendrogram was able to discriminate the emulsions with different formulations into separate classes.     

Multiple Paths to Encephalization and Technical Civilizations

We propose consideration of at least two possible evolutionary paths for the emergence of intelligent life with the potential for technical civilization. The first is the path via encephalization of homeothermic animals; the second is the path to swarm intelligence of so-called superorganisms, in particular the social insects. The path to each appears to be facilitated by environmental change: homeothermic animals by decreased climatic temperature and for swarm intelligence by increased oxygen levels.     

Mating system and brain size in bats

The contribution of sexual selection to brain evolution has been little investigated. Through comparative analyses of bats, we show that multiple mating by males, in the absence of multiple mating by females, has no evolutionary impact on relative brain dimension. In contrast, bat species with promiscuous females have relatively smaller brains than do species with females exhibiting mate fidelity. This pattern may be a consequence of the demonstrated negative evolutionary relationship between investment in testes and investment in brains, both metabolically expensive tissues. These results have implications for understanding the correlated evolution of brains, behaviour and extravagant sexually selected traits.     

Activity levels of bats and katydids in relation to the lunar cycle

Animals are exposed to many conflicting ecological pressures, and the effect of one may often obscure that of another. A likely example of this is the so-called “lunar phobia” or reduced activity of bats during full moon. The main reason for lunar phobia was thought to be that bats adjust their activity to avoid predators. However, bats can be prey, but many are carnivorous and therefore predators themselves. Thus, they are likely to be influenced by prey availability as well as predation risk. We investigated the activity patterns of the perch-hunting Lophostoma silvicolum and one of its main types of prey, katydids, to assess the influence of the former during different phases of the lunar cycle on a gleaning insectivorous bat. To avoid sampling bias, we used sound recordings and two different capture methods for the katydids, as well as video monitoring and radio-telemetry for the bats. Both, bats and katydids were significantly more active during the dark periods associated with new moon compared to bright periods around the full moon. We conclude that foraging activity of L. silvicolum is probably influenced by prey availability to a large extent and argue that generally the causes of lunar phobia are species-specific.     

The chemical composition and energy contents of copepods and cladocerans in relation to their size

The chemical composition and energy contents of four different species of cladocerans, one species of a calenoid copepod, and mixed samples of four species of cyclopoid copepods were quantitatively determined. The relative chemical composition, expressed as a percentage of the total organic matter (excluding chitin) of each of the different species analysed, were very similar. The mean relative composition for all species was 71·2% protein, 9·5% carbohydrates, 19·3% lipids, 16·5% total nitrogen and 2·1% total phosphate–phosphorus. A substantial amount of the total nitrogen was found to be non-protein nitrogen (mean of 23·3% of total nitrogen). The calorific value was calculated from the estimated amounts of proteins, carbohydrates and lipids using conversion factors. The relationship between the calculated organic matter and the chemical oxygen demand (COD) was found to be constant and did not vary much for the different species. The ratio of total organic matter to COD has a mean value of 0·51. Calorific values ranged from 5847 to 6353 cal/g total organic matter. The amounts of chemical substances or energy contents per individual Copepoda or Cladocera were calculated. Regression lines together with their correlation coefficients have been computed to describe the relationship between the amount of chemical constituents and energy contents per individual, and the length of the individual. The results are extensively compared with those given in the literature and differences are discussed.     

Echolocating bats cry out loud to detect their prey

Echolocating bats have successfully exploited a broad range of habitats and prey. Much research has demonstrated how time-frequency structure of echolocation calls of different species is adapted to acoustic constraints of habitats and foraging behaviors. However, the intensity of bat calls has been largely neglected although intensity is a key factor determining echolocation range and interactions with other bats and prey. Differences in detection range, in turn, are thought to constitute a mechanism promoting resource partitioning among bats, which might be particularly important for the species-rich bat assemblages in the tropics. Here we present data on emitted intensities for 11 species from 5 families of insectivorous bats from Panamá hunting in open or background cluttered space or over water. We recorded all bats in their natural habitat in the field using a multi-microphone array coupled with photographic methods to assess the bats' position in space to estimate emitted call intensities. All species emitted intense search signals. Output intensity was reduced when closing in on background by 4-7 dB per halving of distance. Source levels of open space and edge space foragers (Emballonuridae, Mormoopidae, Molossidae, and Vespertilionidae) ranged between 122-134 dB SPL. The two Noctilionidae species hunting over water emitted the loudest signals recorded so far for any bat with average source levels of ca. 137 dB SPL and maximum levels above 140 dB SPL. In spite of this ten-fold variation in emitted intensity, estimates indicated, surprisingly, that detection distances for prey varied far less; bats emitting the highest intensities also emitted the highest frequencies, which are severely attenuated in air. Thus, our results suggest that bats within a local assemblage compensate for frequency dependent attenuation by adjusting the emitted intensity to achieve comparable detection distances for prey across species. We conclude that for bats with similar hunting habits, prey detection range represents a unifying constraint on the emitted intensity largely independent of call shape, body size, and close phylogenetic relationships.     

食鱼蝙蝠形态和行为特化研究

总结了食鱼蝙蝠种类、分布 ,及其形态结构、回声定位功能和捕食行为的研究成果。比较食鱼蝙蝠与近水面“拖网式”食虫蝙蝠在形态、回声定位信号及捕食行为方面的异、同 ,推测食鱼蝙蝠起源于“拖网式”食虫蝙蝠类 ;体形和回声定位信号的几种特异性是捕食行为进化压力 ,而环境是决定因素。     

Encephalization and the evolution of longevity in mammals

Allometric principles account for most of the observed variation in maximum life span among mammals. When body-size effects are controlled for, most of the residual variance in mammalian life span can be explained by variations in brain size, metabolic rate and body temperature. It is shown that species with large brains for a given body size and metabolic rate, such as anthropoid primates, also have long maximum life spans. Conversely, mammals with relatively high metabolic rates and low levels of encephalization, as in most insectivores and rodents, tend to have short life spans. The hypothesis is put forward that encephalization and metabolic rate, which may govern other life history traits, such as growth and reproduction, are the primary determinants directing the evolution of mammalian longevity.