One of the things about bats that really got me interested (apart from them being really cute!) was that there is always something new to learn about them. When asking the question, “Where do all the bats go in winter?” you may get a stock answer of “usually underground, caves, mines, that kind of place…” But in reality, for most bat species, we don’t really know! When comparing the known summer roosts to the known hibernation roosts there is a big gap in our knowledge – we just don’t know where all the bats go in winter!
As autumn comes, temperatures drop and insects become scarcer. Which means bats start to become less and less active, and begin to enter periods of torpor (a kind of sleepy, inactive state). As winter progresses and temperatures continue to drop, these periods of torpor get longer and longer – until bats enter periods of extended hibernation. For their hibernation sites, bats require temperatures to be relatively constant. Large fluctuations in temperature tend to wake bats up, and if they become active they burn their fat reserves more quickly. This can be very risky as they may need those fat reserves to sustain them through the whole winter. Many bats’ hibernation sites are significant distances from their summer roosts – highlighting the importance of a well-connected and well managed landscape.
The complexity of the different bat species becomes all the more apparent when thinking about hibernation sites.
The 17 different breeding UK species all have individual characteristics. Different habitat requirements, different feeding habits, different maternity roosts – and different hibernation sites. For example, the two long-eared species (that are very similar in appearance) are likely to prefer different hibernation sites. The Grey Long-eared Bat is much less tolerant of cold – which means they are roused more frequently during the winter and tend to lose more weight than Brown Long-eared Bats. This lack of tolerance to cold could also explain their range being restricted to southern England, where higher winter temperatures than most of the UK mean that some insects frequently fly in winter.
As climate change progresses, this could mean the range of the Grey Long-eared Bat will expand northwards – but will there be suitable habitat to support them? This is something that the project aims to ensure by protecting and increasing suitable habitats and improving the connectivity between them.
There is always something new to learn about the natural world, and UK bats are a prime example of this. In the past couple of decades we have seen the separation of two species, (Common and Soprano Pipistrelles in 1999) a new species being discovered (Myotis alcathoe in 2010) and learnt more about the rarity of Grey Long-eared Bats, and the reasons for this - prompting this project.
With so much more to discover about bats, who knows - one day we might find out where they all go in winter!
If you live in the project area, would like to volunteer or find out more about this threatened species, please do get in touch (details below).
Grey Long-eared Bat Project Officer (Bat Conservation Trust).