This work highlights the power of long-term individualized monitoring! Frauke deserves immense credit for her perseverance and diligence in running this unique study site. 💪🫶

Bottom line: bat hibernation phenology can respond rapidly to climate change, but these shifts can’t continue forever. Now, more than ever, we need high-quality monitoring data to track bat population trends over the next decades. (Like:
batlas.info/en/trends/my...)

This may also come with risks, as sudden/early cold snaps may leave them with insufficient reserves. Such an event happened in the winter of 2010/11 in this population, resulting in ±60% winter mortality.

Finally, what about the Natterer’s? It's likely that they will become increasingly active in winter, only showing up at hibernacula during particularly cold periods (not unlike Barbastelle bats).

Whatever the reason, the current rate of shift is likely unsustainable long-term. Hibernation entry is already encroaching on the mating period, and the fat reserves these little fluffballs can accumulate is limited. What happens when limits are reached? Time will tell, but I fear it won’t be good

Indeed, we observe almost no weight gain in juveniles throughout autumn capture season, which contrasts strongly with adults.

This scenario may be particularly problematic for juvenile Daubenton’s, as their entry into the hibernaculum has not shifted to the same degree as in adults. Having only been born a few months prior, they may simply need more time to fully develop and learn how to hunt effectively.

Accumulating fat for winter is a tricky task for bats. The fatter they get, the more energetically costly it becomes to fly. So in order to keep ‘putting on the grams’, bats need progressively higher prey densities. With insect peaks shifting earlier, Daubs may have no choice but to shift along

In the most optimistic scenario, Daubenton’s bats are taking advantage of this shift, fattening up quickly, and diving into the safety of the hibernaculum as soon as they can. However, it could also be an attempt to make the best of a bad job...

Daubenton’s are specialists at scooping insects off water bodies (trawling). As water bodies have gotten warmer, peaks in insect emergence from these water bodies have advanced. As a result, the last big peak of prey availability for the Daubenton’s in late summer is getting earlier and earlier.

Surprisingly, Daubenton’s bats (at the same site and over the same time-frame) have EXTENDED their hibernation duration, with adult bats entering the hibernaculum much earlier than they used to (males: 2 days/year, females 1 day/year). But why? We think in response to their prey…

With temps rising, winters are getting milder and shorter, causing many organisms to extend their active periods in autumn and spring.
Natterer’s bats are doing this at an exceptional rate! Entering later, emerging earlier, reducing their hibernation period by nearly a month in just over a decade!

We're looking for a PhD candidate who will characterise what echolocating agents do in groups using a multi-sensor rigs in the field. Wouldn't it be cool to finally figure out how bats manage their calling and flying - and even reconstruct what they may be hearing to make these decisions? 5/n

Systematic genetic monitoring of the species would be an incredibly valuable tool to track population dynamics, and we hope our work inspires the establishment of such a program! (6/6)
Big shoutout to the entire team that made this work possible! (none on Bsky unfortunately)

While the study only covered 4 years, we did observe a very subtle reduction in allelic richness (genetic diversity) over time, suggesting that the population may be declining. This fits to observations that it is amongst the most frequently observed bat fatalities at wind farms across Europe. (5/6)

More broadly, we found that the population is genetically very well-mixed and shows no signs of sub-structuring, suggesting the entire catchment area that passes through the Netherlands on their migration acts as a single genetic population. (4/6)

Turns out, this is not the case, as we found no mother-offspring pairs in any of the individuals sampled together, or even across the entire 4 year dataset. (3/6)

In autumn, male bats defend roosting sites along the migratory pathway, and try to attract females that are passing by to stopover and mate. We noticed that juveniles often stopped at these roosts together with the adult females. So we wondered whether mothers and their offspring migrate together?