Intra-specific variation in wing morphology and its impact on take-off performance in blue tits (Cyanistes caeruleus) during escape flights

Diurnal and seasonal increases in body mass and seasonal reductions in wing area may compromise a bird's ability to escape, as less of the power available from the flight muscles can be used to accelerate and elevate the animal's centre of mass. Here, we investigated the effects of intra-specific variation in wing morphology on escape take-off performance in blue tits (Cyanistes caeruleus). Flights were recorded using synchronised high-speed video cameras and take-off performance was quantified as the sum of the rates of change of the kinetic and potential energies of the centre of mass. Individuals with a lower wing loading, WL (WL=body weight/wing area) had higher escape take-off performance, consistent with the increase in lift production expected from relatively larger wings. Unexpectedly, it was found that the total power available from the flight muscles (estimated using an aerodynamic analysis) was inversely related to WL. This could simply be because birds with a higher WL have relatively smaller flight muscles. Alternatively or additionally, variation in the aerodynamic load on the wing resulting from differences in wing morphology will affect the mechanical performance of the flight muscles via effects on the muscle's length trajectory. Consistent with this hypothesis is the observation that wing beat frequency and relative downstroke duration increase with decreasing WL; both are factors that are expected to increase muscle power output. Understanding how wing morphology influences take-off performance gives insight into the potential risks associated with feather loss and seasonal and diurnal fluctuations in body mass

Landscape scale habitat suitability modelling of bats in the Western Ghats of India: Bats like something in their tea

To conserve biodiversity it is imperative that we understand how different species respond to land use change, and determine the scales at which habitat changes affect species' persistence. We used habitat suitability models (HSMs) at spatial scales from 100-4000. m to address these concerns for bats in the Western Ghats of India, a biodiversity hotspot of global importance where the habitat requirements of bats are poorly understood. We used acoustic and capture data to build fine scale HSMs for ten species (Hesperoptenus tickelli, Miniopterus fuliginosus, Miniopterus pusillus, Myotis horsfieldii, Pipistrellus ceylonicus, Megaderma spasma, Hipposideros pomona, Rhinolophus beddomei, Rhinolophus indorouxii and Rhinolophus lepidus) in a tea-dominated landscape. Small (100-500. m) scale habitat variables (e.g. percentage tea plantation cover) and distances to habitat features (e.g. distance to water) were the strongest predictors of bat occurrence, likely due to their high mobility, which enables them to exploit even small or isolated foraging areas. Most species showed a positive response to coffee plantations grown under native shade and to forest fragments, but a negative response to more heavily modified tea plantations. Two species were never recorded in tea plantations. This is the first study of bats in tea plantations globally, and the first ecological Old World bat study to combine acoustic and capture data. Our results suggest that although bats respond negatively to tea plantations, tea-dominated landscapes that also contain forest fragments and shade coffee can nevertheless support many bat species

A New Metaheuristic Bat-Inspired Algorithm

Metaheuristic algorithms such as particle swarm optimization, firefly algorithm and harmony search are now becoming powerful methods for solving many tough optimization problems. In this paper, we propose a new metaheuristic method, the Bat Algorithm, based on the echolocation behaviour of bats. We also intend to combine the advantages of existing algorithms into the new bat algorithm. After a detailed formulation and explanation of its implementation, we will then compare the proposed algorithm with other existing algorithms, including genetic algorithms and particle swarm optimization. Simulations show that the proposed algorithm seems much superior to other algorithms, and further studies are also discussed.Comment: 10 pages, 2 figure

The mechanical properties of fish myotomal muscle

CHAPTER 1 A brief introduction is given to the structure, biochemistry and electrophysiological and mechanical properties of fish muscle. CHAPTER 2 1. The neuromuscular end plates and preterminal axons of cod, Gadus morhua, fast myotomal muscle were stained for cholinesterase activity. 2. The number of end plates per fibre on superficial fast fibres (17.88 ± 2.13, mean ± 1 S.D.) was significantly higher than that of deep fast fibres (14.79 ± 2.48, P<< 0.001). A small degree of multi-terminal innervation was noted. The end plates showed a great variety in structure and size. 3. Fast muscle contains fibres with a wide range of diameters (20-240 µm). However, no correlation was found between the number of end plates per fibre and fibre diameter. CHAPTER 3 1. The force-velocity characteristics of threads of natural actomyosin, and purified component proteins, from dogfish fast and slow muscle, and rabbit fast skeletal and cardiac muscle have been investigated. 2. Maximum isometric tensions were around 30-70 g cm⁻². The time taken to reach full tension after activation with ATP was 2-8 min. 3. Force-velocity curves obtained could be fitted to a linear form of Hill's equation (1938). In common with intact and skinned fibre studies, points below 0.7 P₀ were found to lie on a straight line. 4. Maximum contraction velocities were around 10⁻² Ls⁻¹, 2-3 orders of magnitude lower than those of intact muscle fibres. 5. The relative velocities of the different thread types do not reflect those of the corresponding muscles, on the basis of measurements on intact fibres, and on measurements of actomyosin/myofibrillar ATPase activities. 6. It is concluded that filament formation, geometry and packing, and not differences in cross bridge cycling rates, largely determine the observed properties of actomyosin threads. CHAPTER 4 A description of the apparatus used to study the isometric and isotonic properties of skinned fibres is given, together with the methods and protocol used in Chapters 5-7. CHAPTER 5 1. The pCa-tension relationship of cod, Gadus morhua, and dogfish, Scyliorhinus canicula, fast and slow skinned fibres isolated from the myotomal muscles was investigated. 2. Maximum isometric tensions were 1.9 ± 0.12 (mean ± 1 S.E.) (fast) and 0.85 ± 0.10 (slow) for cod fibres, and 1.87 ± 0.09 (fast) and 0.84 ± 0.04 (slow) for dogfish (All values : kg cm⁻²). 3. Sigmoid pCa-tension curves were obtained for all fibre types. Values for the half maximally activating [Ca²⁺], and n, the minimum number of Ca²⁺ binding sites involved in activation, were calculated: Thus, the minimum number of Ca²⁺ binding sites in cod is two, in dogfish, four. In both fish, greater cooperativity is exhibited by the fast muscle. CHAPTER 6 1. Force-velocity curves were derived from fast and slow skinned fibres isolated from cod and dogfish myotomal muscles. 2. The extrapolated V and the constants a and b were calculated max from a linear form of Hill's equation: 3. These results are discussed with reference to previous studies of the P-V relationship in amphibian and mammalian muscle. The relationship between a/P₀ and efficiency, and its bearing on the present results is discussed.4. Velocity transients showed a small departure from linearity in all experiments, with velocity decreasing continuously during release (usually < 25% over the first 250 ms after release). This is a feature common to many previous experiments on skinned and intact fibres. The decrease in velocity during release was particularly marked in cod slow fibres. Similar results have been reported in amphibian slow muscle. CHAPTER 7 1. Contraction velocity at low loads was studied in dogfish fast fibres during maximal and submaximal activations. 2. The velocity of contraction during the second 50 ms interval after the onset of release was reduced significantly at low [Ca²⁺], The shape of the velocity transient was found to be dependent on [Ca²⁺]. The rate of decrease of velocity was greater in submaximal than in maximal activations. 3. A brief review of previous studies on the dependence of Vmax on max [Ca²⁺] is given. 4. The results are discussed in the light of recent evidence for length dependent changes in the contractile system. Possible mechanisms for a Ca²⁺ and length dependent inactivation process are considered. CHAPTER 8 The major outstanding problems are stated, and suggestions are made for further work which may give a greater insight into the molecular events underlying contraction in fish muscle. (Abstract shortened

Sex biases in bird and mammal natural history collections.

Natural history specimens are widely used across ecology, evolutionary biology and conservation. Although biological sex may influence all of these areas, it is often overlooked in large-scale studies using museum specimens. If collections are biased towards one sex, studies may not be representative of the species. Here, we investigate sex ratios in over two million bird and mammal specimen records from five large international museums. We found a slight bias towards males in birds (40% females) and mammals (48% females), but this varied among orders. The proportion of female specimens has not significantly changed in 130 years, but has decreased in species with showy male traits like colourful plumage and horns. Body size had little effect. Male bias was strongest in name-bearing types; only 27% of bird and 39% of mammal types were female. These results imply that previous studies may be impacted by undetected male bias, and vigilance is required when using specimen data, collecting new specimens and designating types.Copyright and usage: © 2019 The Author(s) Published by the Royal Society. All rights reserved The attached file is the final approved manuscript (Author Generated Postprint), you are advised to consult the publisher’s version if you wish to cite from it

Variable ranking and selection with random forest for unbalanced data

When one or several classes are much less prevalent than another class (unbalanced data), class error rates and variable importances of the machine learning algorithm random forest can be biased, particularly when sample sizes are smaller, imbalance levels higher, and effect sizes of important variables smaller. Using simulated data varying in size, imbalance level, number of true variables, their effect sizes, and the strength of multicollinearity between covariates, we evaluated how eight versions of random forest ranked and selected true variables out of a large number of covariates despite class imbalance. The version that calculated variable importance based on the area under the curve (AUC) was least adversely affected by class imbalance. For the same number of true variables, effect sizes, and multicollinearity between covariates, the AUC variable importance ranked true variables still highly at the lower sample sizes and higher imbalance levels at which the other seven versions no longer achieved high ranks for true variables. Conversely, using the Hellinger distance to split trees or downsampling the majority class already ranked true variables lower and more variably at the larger sample sizes and lower imbalance levels at which the other algorithms still ranked true variables highly. In variable selection, a higher proportion of true variables were identified when covariates were ranked by AUC importances and the proportion increased further when the AUC was used as the criterion in forward variable selection. In three case studies, known species–habitat relationships and their spatial scales were identified despite unbalanced data

An Exercise-Induced Improvement In Isolated Skeletal Muscle Contractility Does Not Affect The Performance-Enhancing Benefit Of 70 [Mu]M Caffeine Treatment.

This study aimed to examine the effects of exercise-induced increases in skeletal muscle contractile performance on isolated skeletal muscle caffeine sensitivity. 30-week old CD1 mice (n=28) either acted as controls or underwent eight weeks of voluntary wheel running. Following the treatment intervention, whole soleus (SOL) or a section of the costal diaphragm (DIA) was isolated from each mouse and tested to determine the effect of 70μM caffeine on work loop power output. Although caffeine elicited a significant increase in power of both the SOL and the DIA, relative to a non-caffeine control, the effect was not different between the experimental groups, despite the muscles of the trained group producing significantly greater muscle power. There was no significant relationship between training volume or baseline work loop power and the caffeine response. These results indicate that an exercise-induced increase in muscle performance did not influence the performance-enhancing effects of caffeine.N/

Bats in the Ghats: Agricultural intensification reduces functional diversity and increases trait filtering in a biodiversity hotspot in India

The responses of bats to land-use change have been extensively studied in temperate zones and the neotropics, but little is known from the palaeotropics. Effective conservation in heavily-populated palaeotropical hotspots requires a better understanding of which bats can and cannot survive in human-modified landscapes. We used catching and acoustic transects to examine bat assemblages in the Western Ghats of India, and identify the species most sensitive to agricultural change. We quantified functional diversity and trait filtering of assemblages in forest fragments, tea and coffee plantations, and along rivers in tea plantations with and without forested corridors, compared to protected forests. Functional diversity in forest fragments and shade-grown coffee was similar to that in protected forests, but was far lower in tea plantations. Trait filtering was also strongest in tea plantations. Forested river corridors in tea plantations mitigated much of the loss of functional diversity and the trait filtering seen on rivers in tea plantations without forested corridors. The bats most vulnerable to intensive agriculture were frugivorous, large, had short broad wings, or made constant frequency echolocation calls. The last three features are characteristic of forest animal-eating species that typically take large prey, often by gleaning. Ongoing conservation work to restore forest fragments and retain native trees in coffee plantations should be highly beneficial for bats in this landscape. The maintenance of a mosaic landscape with sufficient patches of forest, shade-grown coffee and riparian corridors will help to maintain landscape wide functional diversity in an area dominated by tea plantations