Variability and repeatability of noctule bat migration in Central Europe: evidence for partial and differential migration

Abstract

Each year, large numbers of bats move across Europe between their summer and winter areas, yet even though many of them are endangered and legally protected, we are unaware about many aspects of their migratory behaviour. Here, taking Nyctalus noctula as a model species, we used stable hydrogen isotopic values in fur ( δ 2 H f ) as an endogenous marker to shed light on the migratory behaviour of more than 1000 bats from hibernacula across Central Europe. Specifically, we asked the following questions: how flexible is migration in temperate zone bats? Which general migration pattern do noctule bats follow? How repeatable and thus predictable is the migratory behaviour of individuals? Do morphological correlates of migration occur in bats? Our study confirmed that noctule bats engage in partial and female-biased migration across Europe, suggesting the strongest migration pressures for northern populations. Further, we revealed a combination of partial and differential migration patterns with highly variable migration distances which lead to a pronounced mixing of different source populations in hibernacula where mating occurs. Most individuals were consistent in their migration strategy over time, i.e. 86% could be repeatedly assigned to either long-distance or regional origin across years. This is consistent with our finding that the between-individual component explained 84% of the variation in δ 2 H f values, suggesting specialized individual migratory behaviours and a strong natal philopatry. We discovered a positive correlation between forearm length and migration distance and support for sex-specific effects of migration on body condition. Our study elucidated migration patterns over large geographical scales, demonstrating that considerable numbers of migratory bats originating from distant populations depend on hibernacula across Central Europe, calling for international conservation management.

Using trace elements to identify the geographic origin of migratory bats

“…However, relative to the use of such approaches to document migratory behavior of birds ( Norris & Marra, 2007 ; Irwin, Irwin & Smith, 2011 ; Hobson et al, 2014 ; Nelson et al, 2015 ), the use of biomarkers to track migration in migratory bats is relatively unexplored. To date, the most common type of biomarker used in bats has been stable hydrogen isotopes, which has provided some insights to their migratory behaviors (e.g., Cryan et al, 2004 ; Fraser et al, 2012 ; Ossa et al, 2012 ; Fraser, Brooks & Longstaffe, 2017 ; Lehnert et al, 2018 ). However, hydrogen isotopes are most useful for identifying broad patterns of latitudinal or elevational migration, whereas they are less useful along longitudinal gradients ( Voigt & Lehnert, 2019 ).…”

Nathusius' bats optimize long-distance migration by flying at maximum range speed

“…Migration between summer and wintering habitats has been recorded in several bat species (Fleming and Eby, 2003;Steffens et al, 2004;Hutterer et al, 2005;Popa-Lisseanu and Voigt, 2009;Voigt et al, 2014;Lehnert et al, 2018). However, compared with the large amount of information available on migration in other taxa, bat migration has received little attention.…”

Windenergievorhaben und Fledermausschutz: Was fordern Expert*innen zur Lösung des Grün-Grün-Dilemmas?

“…Ein weiteres Kriterium für die Erteilung von Ausnahmen gemäß §45 BNatSchG ist der günstige Erhaltungs-zustand der Populationen, der sich nicht verschlechtern darf. Aus wissenschaftlicher Sicht sind Populationsgrößen von Fledermäusen nur schwer zu ermitteln und kumulative Effekte auf die Gesamtpopulationen nicht auszuschließen (Lehnert et al 2018;Lindemann et al 2018;Fritze et al 2019).…”