John D. Altringham

Bats : biology and behaviour

Introduction 1. The evolution and diversity of bats 2. Bat flight 3. Echolocation 4. Torpor and hibernation 5. Reproduction and development 6. Behavioural ecology 7. Community ecology and the interactions between bats and other organisms 8. Conservation References Index

Old World fruit bats can be long–distance seed dispersers through extended retention of viable seeds in the gut

Seed dispersal and pollination by animals play a crucial role in the maintenance of forest ecosystems worldwide. Frugivorous bats are important pollen and seed dispersers in both the Palaeo– and Neotropics, and at least 300 plant species are known to rely on Old World fruit bats (Megachiroptera, Pteropodidae) for their propagation. However, rapid food transit times (generally less than 30 minutes) in frugivorous bats have been thought to limit their ability to disperse seeds to just a few tens of kilometres. Here we demonstrate regular daytime (>12 hours) retention of food and viable fig seeds (Ficus, Moraceae) in the gut of the Old World fruit bat Cynopterus sphinx: a behaviour not previously reported for any frugivorous bat. Field observations indicate that this behaviour also occurs in other genera. Old World fruit bats are highly mobile and many species undertake considerable foraging and migration flights. Our findings indicate that Old World fruit bats have the potential to disperse small seeds hundreds of kilometres. This necessitates a reappraisal of their importance in transporting zoochorous seeds to remote areas and facilitating gene flow between isolated populations of plants, both within mainlands and across ocean barriers.

The distribution of Daubenton's bats (Myotis daubentonii) and pipistrelle bats (Pipistrellus pipistrellus) (Vespertilionidae) in relation to small-scale variation in riverine habitat.

The distribution of foraging Myotis daubentonii and Pipistrellus pipistrellus bats (Vespertilionidae) was investigated along an upland river in relation to the smoothness of the water surface and the extent of bankside vegetation. It was found that both bat species significantly preferred sections of the river with smooth water surfaces and trees on both banks. The abundance of insects flying just above the water surface was also significantly greater in sections with a smooth water surface with trees on both sides. The distribution of bats thus probably correlated with the higher densities of insects, and may also have been related to the avoidance of noise from rough water areas which interferes with echolocation. The results suggest that in upland river systems, maintenance and enhancement of bankside vegetation and tree cover in association with the maintenance and enhancement of a mosaic of water surfaces (to include some smooth water where trees are present) will increase the value of the riverine habitat to bats.

Genetic population structure of Natterer's bats explained by mating at swarming sites and philopatry.

During autumn ‘swarming’, large numbers of temperate bats chase each other in and around underground sites. Swarming has been proposed to be a mating event, allowing interbreeding between bats from otherwise isolated summer colonies. We studied the population structure of the Natterers bat (Myotis nattereri), a swarming species in northern England, by sampling bats at seven sites in two swarming areas and at 11 summer colonies. Analysis of molecular variance (amova) and genetic assignment analyses showed that the swarming areas (60 km apart) support significantly different populations. A negative correlation was found between the distance of a summer colony from a swarming area and the assignment of bats to that area. High gene diversity was found at all sites (HE = 0.79) suggesting high gene flow. This was supported by a low FST (0.017) among summer colonies and the absence of isolation by distance or substructure among colonies which visit one swarming area. The FST, although low, was significantly different from zero, which could be explained by a combination of female philopatry and male‐mediated gene flow through mating at swarming sites with bats from other colonies. Modelling suggested that if effective size of the summer colonies (Ne) was low to moderate (10–30), all mating must occur at the swarming sites to account for the observed FST. If the Ne was higher (50), in addition to random mating during swarming, there may be nonrandom mating at swarming sites or some within‐colony mating. Conservation of swarming sites that support potentially large populations is discussed.

THE pCa-TENSION AND FORCE-VELOCITY CHARACTERISTICS OF SKINNED FIBRES ISOLATED FROM FISH FAST AND SLOW MUSCLES

1. Single fast fibres and small bundles of two to six slow fibres were dissected from the myotomal muscles of the cod, Gadus morhua, and the dogfish, Scyliorhinus canicula. Fibres were chemically skinned with the non‐ionic detergent Brij 58.

Isometric and isotonic muscle properties as determinants of work loop power output

The power output of rabbit latissimus dorsi muscle was calculated under isotonic conditions and during oscillatory work. Isotonic shortening studies yielded a maximum power output of 120 W·kg−1 at a P/P0 of 0.4 compared to a maximum power output of 32 W·kg−1 obtained using the work loop technique. This difference can largely be explained by comparing actual work loops with those constructed using force velocity (P/V) and isometric data. At low cycle frequencies, work loop power output is quite close to that predicted from P/V and isometric data. However, at higher frequencies other dynamic muscle properties appear to exert a more marked effect.

Evolutionary adaptation of muscle power output to environmental temperature: force-velocity characteristics of skinned fibres isolated from antarctic, temperate and tropical marine fish.

Abstract1.Single fast fibres were isolated from the myotomal muscles of icefish (Chaenocephalus aceratus Lönnberg, Antarctica), North Sea Cod (Gadus morhua L.) and Pacific Blue Marlin (Makaira nigricans Wakiya, Hawaii). Fibres were chemically skinned with the non-ionic detergent Brij-58.2.Maximum tensions (Po, kN m−2) developed at the characteristic body temperature of each species are 231 for icefish (−1°C), 187 for cod (8°C) and 156 for marlin (20°C). At 0°CPo is 7 times higher for fibres from the icefish than from the marlin.3.Fibres from icefish and cod failed to relax completely following activations at temperatures above approximately 12°C. The resultant post-contraction force is associated with a proportional increase in stiffness, suggesting the formation of a population of Ca-insensitive cross bridges.4.At 0°C there is little interspecific variation in unloaded contraction velocity (Vmax) among the three species.Vmax (muscle lengths s−1) at normal body temperatures are 0.9 for icefish (−1°C), 1.0 for cod (8°C) and 3.4 for marlin (20°C).5.The force-velocity (P-V) relationship becomes progressively more curved with increasing temperature for all three species.6.Maximum power output for the fast muscle fibres from the Antarctic species at −1°C is around 60% of that of the tropical fish at 20°C. Evolutionary temperature compensation of muscle power output appears largely to involve differences in the ability of cross bridges to generate force.

Effects of phosphate on the contractile properties of fast and slow muscle fibres from an Antarctic fish.

Single fast myotomal fibres and small bundles of slow fibres (from the adductor pectoralis profundus muscle) were isolated from the Antarctic teleost Notothenia neglecta. Fibres were skinned by a brief detergent treatment. The effects of phosphate on the mechanical properties and ATPase activity of fast and slow fibres were studied. 20 mM‐phosphate inhibited maximum isometric tension in slow fibres by 34%, but by only 11% in fast fibres. A half‐maximal response was obtained at approximately 5 mM‐phosphate. These concentrations are within the range measured in muscle, and the effect is probably of physiological significance. This species is of particular interest, since there is evidence that the energy supply to the fast muscle is largely based on phosphocreatine breakdown, which would result in large changes in intracellular phosphate concentration during exercise. The maximum contraction velocity of both fast and slow fibres was not affected by 10 mM‐phosphate, nor was the ATPase activity of the slow fibres during isometric contraction. The phosphate‐induced depression in tension in slow fibres was associated with a proportional decrease in stiffness. The rate of force recovery after rapid, small amplitude stretches and releases was increased by phosphate, as was the rate of rise of force during stretch activation. The results are discussed with reference to the different patterns of energy supply for contraction in muscle, and an attempt is made at explaining the data in terms of changes in cross‐bridge kinetics.

Identification of bat species in Greece from their echolocation calls

ABSTRACT Bats are the second most speciose order of mammals and are under significant threat throughout the world. Survey and monitoring of bats for conservation are severely hampered by the lack of a reliable and user-friendly method of identifying bats from their echolocation calls. We recorded and described time-expanded echolocation calls from 23 bat species in the National Park of Dadia-Lefkimi-Soufli, Greece. We compared the performance of quadratic and linear discriminant function analysis (DFA) of calls as a means of identifying species. Quadratic rather than linear DFA has been used by several researchers because of the violation of the methods basic assumption (homogeneity of variance-covariance matrices). However, when linear DFA was applied for the classification of recorded species in this study, correct classification rate was identical to the quadratic functions (82.4%) and linear models did not misclassify bats to the species with the greatest dispersion, the main problem caused by violation of the homogeneity assumption. The advantage of linear DFA is that it provides discriminant function coefficients. The linear combination of these coefficients and parameters from calls from unidentified bats can be used for species identification without access to the original data sets, an option not provided by quadratic analysis. When separate models were developed for Myotis species and for FM/QCF species, correct classification rates increased to 84.8% and 93.4%, respectively. DF coefficients thus provide a reliable identification tool, but intraspecific geographic variation must be taken into account.

The mechanical properties of polyneuronally innervated, myotomal muscle fibres isolated from a teleost fish (Myoxocephalus scorpius)

Single or small bundles of fibres were isolated from the abdominal myotomes of the sculpinMyoxocephalus scorpius, a teleost with a polyneuronal pattern of fast muscle innervation. Fibres responded to a supra-threshold stimulus with an all-or-none twitch. Tetanic fusion frequency at 3°C was 40–60 Hz, and the twitch tetanus ratio 0.70. Maximum isometric tension was 281 kN m−2. Similar isometric contractile properties were obtained from the focally innervated fast muscle fibres of another teleost, the eel,Anguilla anguilla. The response of sculpin fibres to stretch during tetanus was similar to that reported for frog twitch fibres. A 5% stretch of 25–50 ms duration increased force to 1.4P0 which decayed to a steady level 5–10% above that of a control tetanus. The force-velocity relationship was also studied. Maximum contraction velocity was 4.75 Ls−1. Force-velocity data were not adequately described by a simple hyperbola. Alternative methods of curve fitting have been explored and discussed.