title: Tracking post-hibernation behavior and early migration does not reveal the expected sex-differences in a "female-migrating" bat.
abstract: Long-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.
authors.affiliation: Max Planck Institute for Ornithology, Department of Migration and Immuno-Ecology, Am Obstberg 1, 78315 Radolfzell, Germany; University of Konstanz, Department of Biology, 78457 Konstanz, Germany; Smithsonian Tropical Research Institute, Balboa, Ancón, Panama.
authors.forename: Dina K N
authors.initials: DK
authors.lastname: Dechmann
authors.affiliation: Max Planck Institute for Ornithology, Department of Migration and Immuno-Ecology, Am Obstberg 1, 78315 Radolfzell, Germany; University of Konstanz, Department of Biology, 78457 Konstanz, Germany; Smithsonian Tropical Research Institute, Balboa, Ancón, Panama.
authors.forename: Martin
authors.initials: M
authors.lastname: Wikelski
authors.affiliation: University of Konstanz, Department of Biology, 78457 Konstanz, Germany.
authors.forename: Katarina
authors.initials: K
authors.lastname: Varga
authors.affiliation: University of Konstanz, Department of Biology, 78457 Konstanz, Germany.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Yohannes
authors.affiliation: Max Planck Institute for Ornithology, Department of Migration and Immuno-Ecology, Am Obstberg 1, 78315 Radolfzell, Germany; University of Konstanz, Department of Biology, 78457 Konstanz, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Fiedler
authors.affiliation: Max Planck Institute for Ornithology, Department of Migration and Immuno-Ecology, Am Obstberg 1, 78315 Radolfzell, Germany; University of Konstanz, Department of Biology, 78457 Konstanz, Germany.
authors.forename: Kamran
authors.initials: K
authors.lastname: Safi
authors.affiliation: Gumpisloch 2, 8597 Landschlacht, Switzerland.
authors.forename: Wolf-Dieter
authors.initials: WD
authors.lastname: Burkhard
authors.affiliation: Max Planck Institute for Ornithology, Department of Migration and Immuno-Ecology, Am Obstberg 1, 78315 Radolfzell, Germany; University of Konstanz, Department of Biology, 78457 Konstanz, Germany; Smithsonian Tropical Research Institute, Balboa, Ancón, Panama.
authors.forename: M Teague
authors.initials: MT
authors.lastname: O'Mara
mesh_terms: D025041:Animal Migration; D000818:Animals; D001835:Body Weight; D002685:Chiroptera / Q000254:growth & development / Q000502:physiology*; D004032:Diet; D005260:Female; D006197:Hair; D006605:Hibernation; D008297:Male; D018978:Molting; D012621:Seasons; D012727:Sex Characteristics