Long-term individualized monitoring of sympatric bat species reveals distinct species- and demographic differences in hibernation phenology

Abstract

Background Hibernation allows species to conserve energy and thereby bridge unfavorable environmental conditions. At the same time, hibernation imposes substantial ecological and physiological costs. Understanding how hibernation timing differs within and between species can provide insights into the underlying drivers of this trade-off. However, this requires individualized long-term data that are often unavailable. Here, we used automatic monitoring techniques and a reproducible analysis pipeline to assess the individualized hibernation phenology of two sympatric bat species. Our study is based on data of more than 1100 RFID-tagged Daubenton’s bats (Myotis daubentonii) and Natterer’s bats (Myotis nattereri) collected over seven years at a hibernaculum in Germany. We used linear mixed models to analyze species-, sex- and age-specific differences in entrance, emergence and duration of the longest continuous period spent in the hibernaculum. Results Overall, Daubenton’s bats entered the hibernaculum earlier and emerged later than Natterer’s bats, resulting in a nearly twice as long hibernation duration. In both species, adult females entered earlier and emerged from hibernation later than adult males. Hibernation duration was shorter for juveniles than adults with the exception of adult male Natterer’s bats whose hibernation duration was shortest of all classes. Finally, hibernation timing differed among years, but yearly variations in entrance and emergence timing were not equally shifted in both species. Conclusions Our results suggest that even in sympatric species, and across sex and age classes, hibernation timing may be differentially affected by environmental conditions. This highlights the necessity of using individualized information when studying the impact of changing environments on hibernation phenology.

Sex-biased infections scale to population impacts for an emerging wildlife disease

“…Second, more active males may be able to inhibit pathogen growth through euthermia compared to females, as euthermic mammals mount more robust immune defenses than torpid or hibernating mammals (83, 84). Our activity estimates, which are consistent with other studies (61, 85), suggest that vast differences between male and female bats likely contribute to differences in infection.…”

Long-term field study reveals that warmer summers lead to larger and longer-lived females only in northern populations of Natterer’s bats

“…7–10 g, Dietz et al 2016 ) enters hibernation relatively late in autumn compared to other European bat species and shows some foraging activity in the winter season (Hope and Jones 2012 ; Hope et al 2014 ; Meier et al 2022 ). Mating occurs in autumn and winter and Natterer’s bats emerge from hibernation between January and April (Reusch et al 2019 ; Meier et al 2022 ). Female Natterer’s bats give birth to one offspring per year between June and July (Linton and Macdonald 2018 ).…”

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

“…As only one antenna was employed per entrance, we could not directly assess whether a tagged bat entered or left the hibernaculum when detected by the RFID‐logger. Therefore, we defined an arrival period (1 Aug–31 Dec) and a departure period (1 Jan–30 Apr) for each hibernation (H t ) based on activity patterns known from direct observations in the field, light barrier recordings (that count the number of bats entering and emerging) and RFID recordings (as in Meier et al 2022).…”