The risk faced by the early bat: individual plasticity and mortality costs of the timing of spring departure after hibernation

Hibernation is a widespread adaptation in animals to seasonally changing environmental conditions. In the face of global anthropogenic change, information about plastic adjustments to environmental conditions and associated mortality costs are urgently needed to assess population persistence of hibernating species. Here, we used a five-year data set of 1,047 RFID-tagged individuals from two bat species, Myotis nattereri and Myotis daubentonii that were automatically recorded each time they entered or left a hibernaculum. Because the two species differ in foraging strategy and activity pattern during winter, we expected species–specific responses in the timing of hibernation relative to environmental conditions, as well as different mortality costs of early departure from the hibernaculum in spring. Applying mixed-effects modelling, we were able to disentangle population-level and individual-level plasticity in the timing of departure. To estimate mortality costs of early departure, we u..., Bat capture and data logging
We studied arrival (first recorded activity per hibernation period) and timing of departure from the hibernaculum (last recorded activity per hibernation period) of individually marked Natterer’s bats (M. nattereri n = 540) and Daubenton’s bats (M. daubentonii: n = 507) at a hibernaculum in North-Rhine Westphalia (Figure S1) (Stumpf et al. 2017, Meier et al. 2022). We caught bats using harp traps at the entrance of the hibernaculum, sexed them and distinguished two age classes, young of the year (1st hibernation) and adults (>1 hibernation; for details see Reusch et al. 2019). At this site, bats have been marked with individual RFID-tags (ID 100, Trovan) since 2002 for Natterer’s bats and since 2008 for Daubenton’s bats. Here, we focused on the years 2011 to 2015, for which we had continuous monitoring of bats entering and exiting the hibernaculum. All capture and marking were conducted under the permits (50.0835.2.1, 84-02.04.2015.A508, 70.2-2012/0254, 7..., Data file may be opened with excel, any text editor, and R. All Analyses were performed with R.