Paleoecology of early middle Eocene bats from Messel,FRG. aspects of flight,feeding and echolocation

By their diversified flight apparatus Messel bats occupied specific flight niches similar to those of extant tropical bats. The small Palaeochiropteryx tupaiodon is considered to be most specialized for hunting close to the ground and for hovering inside dense vegetation. Contrarily, Hassianycteris spp. most likely were high and fast flyers in the open space.

The analysis of gut contents proves that Palaeochiropteryx spp. exclusively fed on small moths and caddis flies, i.e. slow and low flying insects. For P. tupaiodon this confirms the foraging strategy independently from wing morphology. Hassianycteris spp. preyed mainly on beetles or other insects with thick cuticules.

Inner ears of Messel microbats are less specialized compared to those of recent species. Especially P. tupaiodon shows no acoustical specialization with regard to its hunting habitat. Thus, we assume that during the early evolution of bats the development of different flight styles and wing shapes preceded acoustical refinements of the echolocation system.     

The power requirements (Glossophaginae: Phyllostomidae) in nectar-feeding bats for clinging to flowers

Nectar-feeding bats are the heaviest pollinators exploiting flowers in a hovering foraging mode. As hovering flight is considered to be energetically costly, clinging to flowers would be beneficial from an energetic perspective. I examined the rate of oxygen consumption and carbon dioxide release during clinging flower visitation in two 10-g Glossophaga soricina (Glossophinae: Phyllostomidae) to evaluate the potential energetic benefit of clinging versus hovering. In addition, I measured the duration of flower visits of free-ranging glossophagine bats to Markea neurantha (Solanaceae), a bat-pollinated plant that allows both hovering and clinging flower visitation. After 20 s of clinging to an artificial respiratory mask, the bats respiratory exchange ratio did not significantly deviate from 1, indicating the combustion of sugar. The average oxygen uptake rate equaled 1.39 ml min^–1 (±0.38 SD, STPD) and the carbon dioxide release rate equaled 1.33 ml min^–1 (±0.20 SD, STPD) for feeder visits longer than 20 s (n=79). Converting the oxygen uptake rate into power input yielded 0.49 W, less than a third of the power requirements for hovering for a 10-g bat. Free-ranging 10-g glossophagine bats exploited flowers of M. neurantha for, on average, 0.32 s ( ±0.14 SD, n=273) during hovering and for 0.39 s (±0.18 SD, n=152) during clinging visitations. A comparison between the power requirements of flower exploitation in differently sized bats indicates that clinging would benefit larger nectar-feeding bats to a greater extent than smaller species.Communicated by G. Heldmaier     

食虫蝙蝠与昆虫之间的相互作用和协同进化关系

食虫蝙蝠与昆虫之间是捕食和被捕食的关系,夜行性昆虫是食虫蝙蝠主要的食物来源。在漫长的协同进化中,蝙蝠施加的捕食压力导致夜行性昆虫一系列特征的进化,其中一部分昆虫进化出能听到蝙蝠的超声波信号并采取逃跑行为或者能通过其它方式躲避蝙蝠,同时昆虫的适应性特征同样影响着蝙蝠的回声定位和捕食策略。本文从蝙蝠捕食昆虫的种类、昆虫对蝙蝠捕食的反应和食虫性蝙蝠对昆虫防卫的适应对策等三个方面对食虫蝙蝠与昆虫之间的相互关系进行了概述。     

The role of echolocation in the hunting of terrestrial prey – new evidence for an underestimated strategy in the gleaning bat, Megaderma lyra

The observation that gleaning bats detect prey by its noises, together with difficulties in recording their faint sonar calls, have led some authors to conclude that gleaning bats may not use echolocation in certain hunting situations. In particular, it is conjectured that echolocation plays no role in the classification and tracking of prey. In the present study, we show that the gleaning bat, Megaderma lyra, is able to find silent and motionless prey on the ground. The significance of sonar for catching a variety of terrestrial prey is established in a standardized situation. Sonar calls were found to be emitted during all stages, i.e. approach, hovering above the prey, and return to the roost, of every hunting flight. The harmonic pattern of the calls differed significantly between these stages, calls with three or more prominent components prevailing during hovering. Bats identified prey and rejected dummies while hovering above them. During this stage, increased call rates and reduced call durations were found. Echolocation activity during, and the duration of, the hovering phase depended on prey type, in particular on prey movement. The prey-dependent shifts in sonar activity, the broadband call structure with an emphasis on higher harmonics, and a systematic shift of the calls' peak frequencies during hovering, are discussed as adaptations to identifying prey by sonar.     

Energetic cost of hovering flight in a nectar-feeding bat measured with fast-response respirometry

Hover-feeding glossophagine bats provide, in addition to the hummingbirds, a second vertebrate model for the analysis of hovering flight based on metabolic measurement and aerodynamic theory. In this study, the power input of hovering Glossophaga soricina bats (11.9 g) was measured by standard respirometry and fast-response (<0.2 s) oxygen analysis. Bats needed 5–7 s after a rest-to-flight transition to return to a respiratory steady state. Therefore, only hovering events preceeded by a 7-s flight interval were evaluated. V˙_O2 during hovering fluctuated with a frequency of 3–5 Hz, which corresponded in frequency to the licking movement of the tongue. During hovering, bats often may have hypoventilated as indicated by reduced V˙_O2 and a respiratory exchange ratio (RER) well below the steady-state value of 1. Steady-state oxygen consumption (and derived power input) during hovering was estimated to be 27 (25–29) ml O₂ g⁻¹ h⁻¹ (158 W kg⁻¹ or 1.88 W) in the 11.9-g bats as indicated by three independent findings: (1) V˙_O2 was 26 ml O₂ g⁻¹ h⁻¹ after 6.5 s of hovering, (2) the mean RER during single hovering events was at its steady-state level of 1 only at oxygen uptake rates of 25–29 ml g⁻¹ h⁻¹, and (3) when the oxygen potentially released from estimated oxygen stores was added to the measured oxygen uptake, the upper limit for oxygen consumption during hovering was found to be 29 ml O₂ g⁻¹ h⁻¹. Hovering power input was about 1.2 times the value of minimum flight power input (Winter and von Helversen 1998) and thus well below the 1.7–2.6 difference in power output postulated by aerodynamic theory (Norberg et al. 1993). Mass specific power input was 40% less than in hummingbirds. Thus, within the possible modes of hovering flight, Glossophaga bats seem to operate at the high-efficiency end of the spectrum. Accepted: 28 April 1998     

Pollination of the understorey palm Calyptrogyne ghiesbreghtiana by hovering and perching bats

Inflorescences of the Central American understorey palm Calyptrogyne ghiesbreghtiana offer bats fruit-like flower tissue as reward for visitation. Bats visited the inflorescences in two different modes: frugivores (Phyllostomidae: Stenodermatinae, Carolliinae) foraged on the inflorescence while perched, whereas bats that were primarily nectarivores (Phyllostomidae: Glossophaginae) also consumed flower tissue, but did so while hovering. Fruit set was significantly lower in inflorescences that had received only hovering visits, indicating that perching behaviour offers better possibilities for pollen transfer. The pollination system of C. ghiesbreghtiana is probably adapted to perching frugivorous bats with nectar-specialist Glossophagines as non-optimal participants. Seen in an evolutionary perspective the C. ghiesbreghtiana– glossophagine bat interactions may demonstrate recruitment of new pollinators from non-destructive visitors.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80 , 281–288.     

Energetic cost of hovering flight in nectar-feeding bats (Phyllostomidae: Glossophaginae) and its scaling in moths, birds and bats

Three groups of specialist nectar-feeders covering a continuous size range from insects, birds and bats have evolved the ability for hovering flight. Among birds and bats these groups generally comprise small species, suggesting a relationship between hovering ability and size. In this study we established the scaling relationship of hovering power with body mass for nectar-feeding glossophagine bats (Phyllostomidae). Employing both standard and fast-response respirometry, we determined rates of gas exchange in Hylonycteris underwoodi (7 g) and Choeronycteris mexicana (13–18 g) during hover-feeding flights at an artificial flower that served as a respirometric mask to estimate metabolic power input. The O₂ uptake rate (V˙ _o2) in ml g⁻¹ h⁻¹ (and derived power input) was 27.3 (1.12 W or 160 W kg⁻¹) in 7-g Hylonycteris and 27.3 (2.63 W or 160 W kg⁻¹) in 16.5-g Choeronycteris and thus consistent with measurements in 11.9-g Glossophagasoricina (158 W kg⁻¹, Winter 1998). V˙ _o2 at the onset of hovering was also used to estimate power during forward flight, because after a transition from level forward to hovering flight gas exchange rates initially still reflect forward flight rates. V˙ _o2 during short hovering events (<1.5 s) was 19.0 ml g⁻¹ h⁻¹ (1.8 W) in 16-g Choeronycteris, which was not significantly different from a previous, indirect estimate of the cost of level forward flight (2.1 W, Winter and von Helversen 1998). Our estimates suggest that power input during hovering flight P _h (W) increased with body mass M (kg) within 13–18-g Choeronycteris (n = 4) as P _h  = 3544 (±2057 SE) M ^{1.76 (±0.21 SE)} and between different glossophagine bat species (n = 3) as P _h  = 128 (±2.4 SE) M ^{0.95 (±0.034 SE)}. The slopes of three scaling functions for flight power (hovering, level forward flight at intermediate speed and submaximal flight power) indicate that: 1. The relationship between flight power to flight speed may change with body mass in the 6–30-g bats from a J- towards a U-shaped curve. 2. A metabolic constraint (hovering flight power equal maximal flight power) may influence the upper size limit of 30–35 g for this group of flower specialists. Mass-specific power input (W kg⁻¹) during hovering flight appeared constant with regard to body size (for the mass ranges considered), but differed significantly (P < 0.001) between groups. Group means were 393 W kg⁻¹ (sphingid moths), 261 W kg⁻¹ (hummingbirds) and 159 W kg⁻¹ (glossophagine bats). Thus, glossophagine bats expend the least metabolic power per unit of body mass supported during hovering flight. At a metabolic power input of 1.1 W a glossophagine bat can generate the lift forces necessary for balancing 7 g against gravitation, whereas a hummingbird can support 4 g and a sphingid moth only 3 g of body mass with the same amount of metabolic energy. These differences in power input were not fully explained by differences in induced power output estimated from Rankine-Froude momentum-jet theory. Accepted: 10 November 1998     

Mortality of bats at wind turbines links to nocturnal insect migration?

This note is based on a literature search and a recent review of bat mortality data from wind farms in Europe (published elsewhere). We suggest that mortality of bats at wind turbines may be linked to high-altitude feeding on migrating insects that accumulate at the turbine towers. Modern wind turbines seem to reach high enough into the airspace to interfere with the migratory movements of insects. The hypothesis is consistent with recent observations of bats at wind turbines. It is supported by the observation that mortality of bats at wind turbines is highly seasonal (August–September) and typically peaks during nights with weather conditions known to trigger large-scale migratory movements of insects (and songbirds). We also discuss other current hypotheses concerning the mortality of bats at wind turbines.     

Sugar flux through the flight muscles of hovering vertebrate nectarivores: a review

In most vertebrates, uptake and oxidation of circulating sugars by locomotor muscles rises with increasing exercise intensity. However, uptake rate by muscle plateaus at moderate aerobic exercise intensities and intracellular fuels dominate at oxygen consumption rates of 50 % of maximum or more. Further, uptake and oxidation of circulating fructose by muscle is negligible. In contrast, hummingbirds and nectar bats are capable of fueling expensive hovering flight exclusively, or nearly completely, with dietary sugar. In addition, hummingbirds and nectar bats appear capable of fueling hovering flight completely with fructose. Three crucial steps are believed to be rate limiting to muscle uptake of circulating glucose or fructose in vertebrates: (1) delivery to muscle; (2) transport into muscle through glucose transporter proteins (GLUTs); and (3) phosphorylation of glucose by hexokinase (HK) within the muscle. In this review, we summarize what is known about the functional upregulation of exogenous sugar flux at each of these steps in hummingbirds and nectar bats. High cardiac output, capillary density, and blood sugar levels in hummingbirds and bats enhance sugar delivery to muscles (step 1). Hummingbird and nectar bat flight muscle fibers have relatively small cross-sectional areas and thus relatively high surface areas across which transport can occur (step 2). Maximum HK activities in each species are enough for carbohydrate flux through glycolysis to satisfy 100 % of hovering oxidative demand (step 3). However, qualitative patterns of GLUT expression in the muscle (step 2) raise more questions than they answer regarding sugar transport in hummingbirds and suggest major differences in the regulation of sugar flux compared to nectar bats. Behavioral and physiological similarities among hummingbirds, nectar bats, and other vertebrates suggest enhanced capacities for exogenous fuel use during exercise may be more wide spread than previously appreciated. Further, how the capacity for uptake and phosphorylation of circulating fructose is enhanced remains a tantalizing unknown.     

Do the evolutionary interactions between moths and bats promote niche partitioning between bats and birds?

Ecological theory suggests that the coexistence of species is promoted by the partitioning of available resources, as in dietary niche partitioning where predators partition prey. Yet, the mechanisms underlying dietary niche partitioning are not always clear. We used fecal DNA metabarcoding to investigate the diets of seven nocturnal insectivorous bird and bat species. Low diet overlap (2%–22%) supported resource partitioning among all species. Differences in diet corresponded with species identity, prey detection method, and foraging behavior of predators. Insects with ultrasonic hearing capabilities were consumed significantly more often by birds than bats, consistent with an evolved avoidance of echolocating strategies. In turn, bats consumed a greater proportion of noneared insects such as spruce budworms. Overall, our results suggest that evolutionary interactions among bats and moths translate to dietary niche partitioning and coexistence among bats and nocturnal birds.     

The effect of local land use and loss of forests on bats and nocturnal insects

Land‐use intensification at local and landscape level poses a serious threat to biodiversity and affects species interactions and ecosystem function. It is thus important to understand how interrelated taxa respond to land‐use intensification and to consider the importance of different spatial scales. We investigated whether and how local land‐use intensity and landscape features affect the predator–prey interaction of bats and insects. Bats and nocturnal insects were assessed on 50 grassland sites in the Schorfheide‐Chorin. We analyzed the effect of local land use and distance to forested areas as a proxy for site accessibility on bats and insects and their biological interaction measured in bat's feeding activity. Insect abundance increased with higher land‐use intensity, while size and diversity of insects decreased. In contrast, bat activity, diversity, and species composition were determined by the distance to forested areas and only slightly by land‐use intensity. Feeding attempts of bats increased with higher insect abundance and diversity but decreased with insect size and distance to forested areas. Finally, our results revealed that near forested areas, the number of feeding attempts was much lower on grassland sites with high, compared to those with low land‐use intensity. In contrast, far from forests, the feeding attempts did not differ significantly between intensively and extensively managed grassland sites. We conclude that the two interrelated taxa, bats and insects, respond to land‐use intensification on very different scales. While insects respond to local land use, bats are rather influenced by surrounding landscape matrix. Hereby, proximity to forests reveals to be a prerequisite for higher bat species diversity and a higher rate of feeding attempts within the area. However, proximity to forest is not sufficient to compensate local high land‐use intensity. Thus, local land‐use intensification in combination with a loss of forest remnants weakens the interaction of bats and insects.     

A Review of Research on the Mechanical Design of Hoverable Flapping Wing Micro-Air Vehicles

Most insects and hummingbirds can generate lift during both upstroke and downstroke with a nearly horizontal flapping stroke plane,and perform precise hovering flight.Further,most birds can utilize tails and muscles in wings to actively control the flight performance,while insects control their flight with muscles based on wing root along with wing's passive deformation.Based on the above flight principles of birds and insects,Flapping Wing Micro Air Vehicles(FWMAVs)are classified as either bird-inspired or insect-inspired FWMAVs.In this review,the research achievements on mechanisms of insect-inspired,hoverable FWMAVs over the last ten years(2011-2020)are provided.We also provide the definition,func-tion,research status and development prospect of hoverable FWMAVs.Then discuss it from three aspects:bio-inspiration,motor-driving mechanisms and intelligent actuator-driving mechanisms.Following this,research groups involved in insect-inspired,hoverable FWMAV research and their major achievements are summarized and classified in tables.Problems,trends and challenges about the mechanism are compiled and presented.Finally,this paper presents conclusions about research on mechanical structure,and the future is discussed to enable further research interests.     

Megafauna associations with deepwater corals (Primnoa spp.) in the Gulf of Alaska

Our study showed that one species of water strider (Aquarius najas) dominated the insect fauna (>90% of the biomass) on and near the surface of a small stream in southern Sweden, but the diet of Daubenton's bats (Myotis daubentonii), regularly feeding over the same stream, contained <1% of these insects. To explain why the bats did not eat water striders in proportion to the apparent abundance of these insects, we tested three hypotheses, with the following results: (1) The water striders did not respond to artificial bat calls and therefore their defence against bats is not based on ultrasonic hearing. (2) Water striders hand-fed to the bats were eaten with similar frequency as palatable controls (caddis flies), so there is no evidence that water striders are unpalatable to bats. (3) Attempted prey-captures by the bats occurred less often than expected within 1 m of the bank of the stream (the bank consisted of a stone wall), indicating that the bats' flight or, alternatively, their detection or capture of insects, was difficult within that area, possibly constrained by clutter. At dusk and just before the bats emerged to feed, the water striders moved away from the open water. They remained motionless close to the bank for as long as the bats were active.     

Discrimination of insect wingbeat-frequencies by the batRhinolophus ferrumequinum

Summary Five Greater Horseshoe bats,Rhinolophus ferrumequinum, were trained in a two-alternative forced-choice procedure to discriminate between artificial echoes of insects fluttering at different wingbeat rates. The stimuli were electronically produced phantom targets simulating fluttering insects with various wingbeat frequencies (Figs. 3, 4). Difference thresholds for wingbeat rates of 50 Hz and 100 Hz were determined. For an S+ of 50 Hz the difference threshold values lay between 2.8 and 4.6 Hz for individual bats; with an S+ of 100 Hz they increased to between 9.8 and 12.0 Hz (Figs. 5, 6, Table 1).Three bats, previously trained to discriminate between a S+ of 50 Hz and a S– with a lower wingbeat rate, were tested with higher frequency stimuli. When they had to decide between their old S+ of 50 Hz and either a 60 or 70 Hz echo two bats continued to select the 50 Hz stimulus while the third bat now preferred the faster fluttering insects (Table 2).During the discrimination task the echolocation behavior of the bats was monitored. When the phantom targets were presented all bats increased their duty-cycle of sound emission from about 40% to sometimes near 70%. They did so by either emitting longer echolocation calls or by increasing the sound repetition rate (Figs. 7, 8).The results show that Greater Horseshoe bats can determine the wingbeat rate of flying insects with an accuracy between 6 and 12%. Possible cues for flutter rate determination by cf-fm bats from natural and artificial insect echoes are discussed.Abbreviations DC duty-cycle - PD pulse duration - PI pulse interval - cf constantfrequency - fm frequency modulation     

Effect of emergent aquatic insects on bat foraging in a riparian forest

1. Riparian zones serve several ecological functions for bats. They provide a source of prey and likely provide favourable structural habitats and shelter from predators. Many studies have shown that bats use the space above streams, ponds or riparian vegetation as feeding habitat. These studies, however, have never distinguished between the effects of habitat structure and prey availability on the foraging activities of bats. Such effects can only be distinguished by an experimental approach. We predicted that bat activity along a stream is influenced by the number of emerged aquatic insects. 2. We evaluated the response of terrestrial consumers, insectivorous bats, to changes in the abundance of emergent aquatic insects by conducting a manipulative field experiment. In a deciduous riparian forest in Japan, aquatic insect flux from the stream to the riparian zone was controlled with an insect-proof cover over a 1.2 km stream reach. 3. We estimated the abundance of emergent aquatic and flying terrestrial arthropods near the treatment and control reaches using Malaise traps. The foraging activity of bats was evaluated in both treatment and control reaches using ultrasonic detectors. 4. The insect-proof cover effectively reduced the flux of emergent aquatic insects to the riparian zone adjacent to the treatment reach. Adjacent to the control reach, adult aquatic insect biomass was highest in spring, and then decreased gradually. Terrestrial insect biomass increased gradually during the summer at both treatment and control reaches. 5. Foraging activity of bats was correlated with insect abundance. In spring, foraging activity of bats at the control reach was significantly greater than at the treatment reach, and increased at both sites with increasing terrestrial insect abundance. 6. Our result suggests that the flux of aquatic insects emerging from streams is one of the most important factors affecting the distribution of riparian-foraging bats. As is the case with other riparian consumers, resource subsidies from streams can directly enhance the performance or population density of riparian-dependent bats. To conserve and manage bat populations, it is important to protect not only forest ecosystems, but also adjacent aquatic systems such as streams.     

Orientation to distant sounds by foraging big brown bats (Eptesicus fuscus)

Big brown bats (Eptesicus fuscus) detect and orient toward relatively low-frequency sounds produced by chorusing frogs or groups of stridulating insects. This response occurs at distances of at least 600 m. The bats are also attracted to a broadcasted recording of the sounds. If recently fed, they do not orient to these sounds. Bats that fly toward the most intense sound field locate insects at a significantly greater rate than those that choose another direction. This suggests that the use of these long-distance acoustic cues may be important for locating concentrations of flying insects.     

Vascular–Platelet and Plasma Hemostasis Regulators from Bloodsucking Animals

Saliva of bloodsuckers (leeches, insects, ticks, vampire bats) contains various regulators of some hemostatic stages. This review summarizes information on their structural characteristics and mechanisms of action. Most bloodsuckers are shown to inhibit vascular–platelet hemostasis by blocking collagen induced platelet adhesion/aggregation. Plasma hemostasis is inhibited by blocking activation of factor X or factor Xa directly.     

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.     

Dynamic Flight Stability of a Model Hoverfly in Inclined-Stroke-Plane Hovering

Most hovering insects flap their wings in a horizontal plane,called ‘normal hovering'.But some of the best hoverers,e.g.true hoverflies,hover with an inclined stroke plane.In the present paper,the longitudinal dynamic flight stability of a model hoverfly in inclined-stroke-plane hovering was studied.Computational fluid dynamics was used to compute the aerodynamic derivatives and the eigenvalue and eigenvector analysis was used to solve the equations of motion.The primary findings are as follows.(1) For inclined-stroke-plane hovering,the same three natural modes of motion as those for normal hovering were identified:one unstable oscillatory mode,one stable fast subsidence mode,and one stable slow subsidence mode.The unstable oscillatory mode and the fast subsidence mode mainly have horizontal translation and pitch rotation,and the slow subsidence mode mainly has vertical translation.(2) Because of the existence of the unstable oscillatory mode,inclined-stroke-plane hovering flight is not stable.(3) Although there are large differences in stroke plane and body orientations between the inclined-stroke-plane hovering and normal hovering,the relative position between the mean center of pressure and center of mass for these two cases is not very different,resulting in similar stability derivatives,hence similar dynamic stability properties for these two types of hovering.     

Wingbeat frequency, temperature and body size in bees and flies

ABSTRACT. This paper describes the relationship between ambient temperature and wingbeat frequency in bees and flies of different sizes, and presents new data from insects in free fight. The slope of the relationship changes with the size of the insect, and was different for insects in hovering flight compared with individuals of the same species in forward flight.