Person: O'Mara, M. Teague
O'Mara, M. Teague
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O'Mara
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M. Teague
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- Data packageData from: European free-tailed bats use topography and nocturnal updrafts to fly high and fast(2021-02-04) O'Mara, M. Teague; Amorim, Francisco; McCracken, Gary F.; Mata, Vanessa; Safi, Kamran; Wikelski, Martin; Beja, Pedro; Rebelo, Hugo; Dechmann, Dina K.N.During the day, flying animals exploit the environmental energy landscape by seeking out thermal or orographic uplift, or extracting energy from wind gradients. However, most of these energy sources are not thought to be available at night because of the lower thermal potential in the nocturnal atmosphere, as well as the difficulty of locating features that generate uplift. Despite this, several bat species have been observed hundreds to thousands of meters above the ground. Individuals make repeated, energetically costly high-altitude ascents, and others fly at some of the fastest speeds observed for powered vertebrate flight. We hypothesized that bats use orographic uplift to reach high altitudes, and that both this uplift and bat high-altitude ascents would be highly predictable. By superimposing detailed three-dimensional GPS tracking of European free-tailed bats (Tadarida teniotis) on high-resolution regional wind data, we show that bats do indeed use the energy of orographic uplift to climb to over 1,600 m, and also that they reach maximum sustained self-powered airspeeds of 135 km h−1. We show that wind and topography can predict areas of the landscape able to support high-altitude ascents, and that bats use these locations to reach high altitudes while reducing airspeeds. Bats then integrate wind conditions to guide high-altitude ascents, deftly exploiting vertical wind energy in the nocturnal landscape.
- Data packageData from: Foraging and roosting behaviour of the fringe-lipped bat, Trachops cirrhosus, on Barro Colorado Island, Panamá(2017-12-18) Hämsch, Frank; O'Mara, M. Teague; Jones, Patricia L.The Neotropical fringe-lipped bat, Trachops cirrhosus, is a generalist predator that hunts frogs and insects by homing in on their mating calls. Although research has examined cognition and prey preferences of bats in captivity, little is known of the foraging or roosting behaviour of this species in the wild. We radio tracked six T. cirrhosus individuals on Barro Colorado Island, Panamá. Bat day roosts were all in hollow cashew trees, Anacardium excelsum, in mixed sex groups of three to five T. cirrhosus individuals, with frequent roost switching. Radio tracked individuals flew an average of 218 ± 227 m from their day roosts to 12.0 ± 10.17 ha foraging areas (50% utilization distribution [UD] kernels = area where bats spent 50% of their time as estimated from a probability distribution). These 50% UD kernels were less than 10% of their average total range use, but larger than previously reported for T. cirrhosus. Radio tracked individuals overlapped in 50% UD kernel foraging areas by only 2.1 ± 5.9 % on average. Foraging behaviour consisted predominantly of short sally flights of less than one minute, indicating bats were likely perch hunting. Bats were more frequently in flight, and had longer flight durations, at the beginning of the night and just before dawn than throughout the rest of the night. These data provide insight into the foraging behaviour of T. cirrhosus in the wild that is a species fast becoming a model system of cognition in captivity.
- Data packageData from: Overall dynamic body acceleration in straw-colored fruit bats increases in headwinds but not with airspeed(2019-05-21) Scharf, Anne K.; Fahr, Jakob; Abedi-Lartey, Michael; Safi, Kamran; Dechmann, Dina K.N.; Wikelski, Martin; O'Mara, M. TeagueAtmospheric conditions impact how animals use the aerosphere, and birds and bats should modify their flight to minimise energetic expenditure relative to changing wind conditions. To investigate how free-ranging straw-colored fruit bats (Eidolon helvum) fly with changing wind support, we use data collected from bats fit with GPS loggers and an integrated triaxial accelerometer and measure flight speeds, wingbeat frequency, and overall dynamic body acceleration (ODBA) as an estimate for energetic expenditure. We predicted that if ODBA reflects energetic expenditure, then we should find a curvilinear relationship between ODBA and airspeed consistent with aerodynamic theory. We expected that bats would lower their airspeed with tailwind support and that ODBA will decrease with increasing tailwinds and increase with wingbeat frequency. We found that wingbeat frequency has the strongest positive relationship with ODBA. There was a small, but negative, relationship between airspeed and ODBA, and bats decreased ODBA with increasing tailwind. Bats flew at ground speeds of 9.6 ± 2.4 ms-1 (mean ± sd, range: 4.3 to 23.9 ms-1) and airspeeds of 10.2 ± 2.5 ms-1, and did not modify their wingbeat frequency with speed. Free-ranging straw-colored fruit bats therefore exerted more total ODBA in headwinds but not when they changed their airspeed. It is possible that the flexibility in wingbeat kinematics may make flight of free-ranging bats less costly than currently predicted or alternatively that the combination of ODBA and airspeed at our scales of measurement does not reflect this relationship in straw-colored fruit bats. Further work is needed to understand the full potential of free-ranging bat flight and how well bio-logging techniques reflect the costs of bat flight.
- Data packageData from: Greater spear nosed bats commute long distances alone, rest together, but forage apart(2023-08-22) O'Mara, M. Teague; Dechmann, Dina K.N.Animals frequently forage in groups on ephemeral resources to profit from social information and increased efficiency. Greater spear-nosed bats, Phyllostomus hastatus, develop group-specific social calls, which are hypothesized to coordinate social foraging to feed on patchily distributed balsa flowers. To test this, we tagged all members of three social groups of P. hastatus on Isla Colo n, Panama , using high-frequency GPS during a season when balsa had begun to flower. We found that bats commuted 20-30 km to foraging sites, more than double the distance reported previously. In contrast to our expectations, we found that tagged individuals did not commute together, but did join group members in small foraging patches with high densities of flowering balsas on the mainland. We hypothesized that close proximity to group members would increase foraging efficiency if social foraging were used to find flower clusters, but distance between tagged individuals did not predict foraging efficiency or energy expenditure. However, decreased distance among tagged bats positively influenced the time spent outside roosting caves and increased the duration and synchrony of resting. These results suggest that social proximity appears to be more important during resting and that factors other than increased feeding efficiency may structure social relationships of group members while foraging. It appears that, depending on the local resource landscape, these bats have an excellent map even of distant resources and may use social information only for current patch discovery. They then may no longer rely on social information during daily foraging.
- Data packageData from: First three-dimensional tracks of bat migration reveal large amounts of individual behavioral flexibility(2019-05-28) O'Mara, M. Teague; Wikelski, Martin; Kranstauber, Bart; Dechmann, Dina K.N.It is generally assumed that small migrating birds and bats explore wind conditions and then choose a flight altitude, which they then maintain. Because of their high metabolism and flight costs, bats should also minimize energy expenditure during migratory flight, but we know little of how individuals make their migratory journeys. We followed migrating common noctules (Nyctalus noctula) fitted with miniaturized barometric pressure radio transmitters by airplane to record three dimensional migratory movements. Mean airspeeds were 7.2-15.9 m/s and overall climb rates were faster than overall descent rates. While all bats migrated in the same northeasterly direction, they showed flexibility in their altitudes, distances and stopover sites both within and among individuals. This suggests that individuals make decisions to take advantage of wind, landscape, and navigational conditions or other, yet unknown factors, to optimize their nightly flights. Our results once more confirm that the flexibility and behavioral repertoire of individuals in the wild is greater than we assume.
- Data packageData from: Common noctules exploit low levels of the aerosphere(2019-02-21) O'Mara, M. Teague; Wikelski, Martin; Kranstauber, Bart; Dechmann, Dina K.N.Aerial habitats present a challenge to find food across a large potential search volume, particularly for insectivorous bats that rely on echolocation calls with limited detection range and may forage at heights over 1000 m. To understand how bats use vertical space, we tracked one to five foraging flights of eight common noctules (Nyctalus noctula). Bats were tracked for their full foraging session (87.27 ± 24 mins) using high-resolution atmospheric pressure radio transmitters that allowed us to calculate height and wingbeat frequency. Bats used diverse flight strategies, but generally flew lower than 40 m, with scouting flights to 100 m and a maximum of 300 m. We found no influence of weather on height and high-altitude ascents were not preceded by an increase in foraging effort. Wingbeat frequency was independent from climbing or descending flight, and bats skipped wingbeats or glided in 10% of all observations. Wingbeat frequency was positively related to capture mass, and wingbeat frequency was positively related to time of night, indicating an effect of load increase over a foraging bout. Overall, individuals used a wide range of airspace including altitudes that put them at increased risk from human-made structures. Further work is needed to test the context of these flight decisions, particularly as individuals migrate throughout Europe.
- Data packageData from: Tracking post-hibernation behavior and early migration does not reveal the expected sex-differences in a "female-migrating“ bat(2015-03-23) Varga, Katarina; Dechmann, Dina K.N.; O'Mara, M. Teague; Wikelski, MartinLong-distance migration is a rare phenomenon in European bats. Genetic analyses and banding studies show that females can cover distances of up to 1,600 km, whereas males are sedentary or migrate only short distances. The onset of this sex-biased migration is supposed to occur shortly after rousing from hibernation and when the females are already pregnant. We therefore predicted that the sexes are exposed to different energetic pressures in early spring, and this should be reflected in their behavior and physiology. We investigated this in one of the three Central European long-distance migrants, the common noctule (Nyctalus noctula) in Southern Germany recording the first individual partial migration tracks of this species. In contrast to our predictions, we found no difference between male and female home range size, activity, habitat use or diet. Males and females emerged from hibernation in similar body condition and mass increase rate was the same in males and females. We followed the first migration steps, up to 475 km, of radio-tagged individuals from an airplane. All females, as well as some of the males, migrated away from the wintering area in the same northeasterly direction. Sex differences in long-distance migratory behavior were confirmed through stable isotope analysis of hair, which showed greater variation in females than in males. We hypothesize that both sexes faced similarly good conditions after hibernation and fattened at maximum rates, thus showing no differences in their local behavior. Interesting results that warrant further investigation are the better initial condition of the females and the highly consistent direction of the first migratory step in this population as summering habitats of the common noctule occur at a broad range in Northern Europe. Only research focused on individual strategies will allow us to fully understand the migratory behavior of European bats.