Overall Dynamic Body Acceleration in Straw-Colored Fruit Bats Increases in Headwinds but Not With Airspeed

O’Mara, M. Teague; Scharf, Anne K.; Fahr, Jakob; Abedi-Lartey, Michael; Wikelski, Martin; Dechmann, Dina K. N.; Safi, Kamran

doi:10.3389/fevo.2019.00200

Cited by 16 publications

(26 citation statements)

References 75 publications

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“…In western sandpipers Calidris mauri and cockatiels Nymphicus hollandicus, wingbeat frequency declined with flight speed in a wind tunnel, while lowest wingbeat frequency was recorded at intermediate speed in teals Anas crecca and thrush nightingales Luscinia luscinia (Pennycuick et al 1996, Hedrick et al 2003, Maggini et al 2017. Outside of avian flight, wingbeat frequency of strawcoloured fruit bats Eidolon helvum, is not modified with changes in speed, again suggesting other wingbeat kinematics may be more important (O'Mara et al 2019). Across a wide variety of birds and bats, flight muscle efficiency decreases with forward speed (Guigueno et al 2019), implying that any change in wingbeat frequency leads to inefficiencies in conversion to mechanical work.…”

Section: Discussionmentioning

confidence: 99%

Coping with the commute: behavioural responses to wind conditions in a foraging seabird

Collins

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Elliott

et al. 2020

Journal of Avian Biology

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Movement is a necessary yet energetically expensive process for motile animals. Yet how individuals modify their behaviour to take advantage of environmental conditions and hence optimise energetic costs during movement remains poorly understood. This is especially true for animals that move through environments where they cannot easily be observed. We examined the behaviour during commuting flights of black‐legged kittiwakes Rissa tridactyla breeding on Middleton Island, Alaska in relation to wind conditions they face. By simultaneously deploying GPS and accelerometer devices on incubating birds we were able to quantify the timing, destination, course and speed of flights during commutes to foraging patches, as well as how wing beat frequency and strength relate to flight speeds. We found that kittiwakes did not preferentially fly in certain wind conditions. However, once in the air they exhibited plasticity through modulation of effort by increasing air speed (the speed at which they fly relative to the wind) when travelling into headwinds and decreasing their air speed when flying with tailwinds. Moreover, we identified a biomechanical link behind this behaviour: that to achieve these changes in flight speeds, kittiwakes altered their wing beat strength, but not wing beat frequency. Using this information, we demonstrate that the cost of flying into a headwind outweighs the energy saving benefit of flying with a tailwind of equivalent speed; therefore, exploiting a tailwind when commuting to a foraging patch would not be beneficial if having to return in the same direction with the same conditions. Our findings suggest that extrinsic factors, such as prey availability, have a more influential role in determining when and where kittiwakes fly during foraging trips than do wind conditions. However, once flying, kittiwakes exhibit behavioural plasticity to minimise transport costs.

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Section: Discussionmentioning

confidence: 99%

Coping with the commute: behavioural responses to wind conditions in a foraging seabird

Collins

Green

Elliott

et al. 2020

Journal of Avian Biology

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“…Data were retrieved using a base station connected to a directional high-gain antenna. Further details on field procedures and the tracking devices can be found in earlier studies that used data from the same bats [ 25 , 26 , 31 , 37 , 40 ].…”

Section: Methodsmentioning

confidence: 99%

“…Bats were captured with mist nets set at the level of the canopy, which disturbed animals that were roosting in the nearby trees, and we expected their escape flights to spread throughout the roost affecting bats tagged in previous trapping sessions. We also assumed that solar irradiance, precipitation and wind speed could potentially influence daytime flight behaviour of bats in the roosts based on earlier studies [34][35][36][37]. These variables were obtained from open access weather databases (http://www.sasscalweathernet.org for Zambia roosts and https://globalweather.tamu.edu for all the others) with a temporal resolution of one day.…”

Section: Predictors Of Roost Disturbance and Natural Stressorsmentioning

confidence: 99%

“…The occurrence of daytime roost flights was then modelled against our activity in the roosts during the days of trapping, as a predictor of roost disturbance, and natural stressors that may influence flight probability during the roosting period. We predicted that: (1) our presence in the roosts will lead to higher daytime flight probability; (2) bats will be more prone to fly in days of high solar irradiance to find shaded perches and avoid heat stress [ 34 , 35 ]; (3) bats will fly less during daytime when it rains, as rain increases flight energy costs [ 36 ]; (4) bats will fly less at higher wind speeds, which might increase flight energy costs [ 37 ].…”

Section: Introductionmentioning

confidence: 99%

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Assessing roost disturbance of straw-coloured fruit bats (Eidolon helvum) through tri-axial acceleration

et al. 2020

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The disturbance of wildlife by humans is a worldwide phenomenon that contributes to the loss of biodiversity. It can impact animals’ behaviour and physiology, and this can lead to changes in species distribution and richness. Wildlife disturbance has mostly been assessed through direct observation. However, advances in bio-logging provide a new range of sensors that may allow measuring disturbance of animals with high precision and remotely, and reducing the effects of human observers. We used tri-axial accelerometers to identify daytime flights of roosting straw-coloured fruit bats (Eidolon helvum), which were used as a proxy for roost disturbance. This bat species roosts on trees in large numbers (often reaching hundreds of thousands of animals), making them highly vulnerable to disturbance. We captured and tagged 46 straw-coloured fruit bats with dataloggers, containing a global positioning system (GPS) and an accelerometer, in five roosts in Ghana, Burkina Faso and Zambia. Daytime roost flights were identified from accelerometer signatures and modelled against our activity in the roosts during the days of trapping, as a predictor of roost disturbance, and natural stressors (solar irradiance, precipitation and wind speed). We found that daytime roost flight probability increased during days of trapping and with increasing solar irradiance (which may reflect the search for shade to prevent overheating). Our results validate the use of accelerometers to measure roost disturbance of straw-coloured fruit bats and suggest that these devices may be very useful in conservation monitoring programs for large fruit bat species.

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“…We used only data from individuals with at least one complete night of tracking, on average: 4.4 ± 1.9 nights (see electronic supplementary material, table S2). We classified the GPS locations into three behaviours (resting, commuting and foraging) before analysing foraging parameters, based on the percentage of flapping flight identified within an accelerometry segment [30] (additional description, see moveACC: https://gitlab.com/anneks/moveACC). The percentage of flapping bouts per GPS fix was used to determine the behavioural classes.…”

Section: Behavioural Classificationmentioning

confidence: 99%

Foraging movements are density-independent among straw-coloured fruit bats

et al. 2020

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Intraspecific competition in large aggregations of animals should generate density-dependent effects on foraging patterns. To test how large differences in colony size affect foraging movements, we tracked seasonal movements of the African straw-coloured fruit bat ( Eidolon helvum ) from four colonies that range from 4000 up to 10 million animals. Contrary to initial predictions, we found that mean distance flown per night (9–99 km), number of nightly foraging sites (2–3) and foraging and commuting times were largely independent of colony size. Bats showed classic central-place foraging and typically returned to the same day roost each night. However, roost switching was evident among individuals in three of the four colonies especially towards the onset of migration. The relatively consistent foraging patterns across seasons and colonies indicate that these bats seek out roosts close to highly productive landscapes. Once foraging effort starts to increase due to local resource depletion they migrate to landscapes with seasonally increasing resources. This minimizes high intraspecific competition and may help to explain why long-distance migration, otherwise rare in bats, evolved in this highly gregarious species.

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Overall Dynamic Body Acceleration in Straw-Colored Fruit Bats Increases in Headwinds but Not With Airspeed

Cited by 16 publications

References 75 publications

Coping with the commute: behavioural responses to wind conditions in a foraging seabird

Coping with the commute: behavioural responses to wind conditions in a foraging seabird

Assessing roost disturbance of straw-coloured fruit bats (Eidolon helvum) through tri-axial acceleration

Foraging movements are density-independent among straw-coloured fruit bats

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