Hibernating bats?

[JohnRoss]

Every year we get bats behind our upstairs shutters in the Summer months. This year they are still there which is strange as in previous years they have usually gone away for their Winter holidays. They look as if they are hibernating or dead and resemble the Common Pipistrelle  though maybe not quite so brown. Does anyone know if this is unusual behavior? It was one of these that came into the bedroom some months ago and was caught by our house cat Ben and gave rise to some concerns about the risk of rabies. With temperatures as low as -4 degrees of late they must be very cold or is this not a problem for a hibernating bat?.........................JR

[Callie]

Hello JR

As with all hibernating creatures, a bat's heartbeat slows right down so the cold is no problem. They usually look for the clichéd cave or somewhere really cool where they will be undisturbed. Because they are in hibernation mode, they will look as if they are dead......but they are very much alive.....just resting......

[JohnRoss]

Hi Callie. I found this note on the net:   "Others, such as the common pipistrelle (Pipistrellus pipistrellus) withdraw to hibernating places at some distance from their summer range."   I just wondered why they had decided to stay behind our shutters this particular year and if this had any particular significance.............................................JR

PS I have had 5 ultrasonic squeakers running in the house to keep Loir away and I wonder if this has had any effect on the bats. The ultrasonic devices operate at a frequency well below the stated bat range but I suppose they might hear the harmonics if the waveform is distorted and maybe they think that there is a large colony here!

[ventodue]

Hi JR,

Bats usually hibernate in a different place to either their summer (maternity) roost sites or their rest sites (most species spend a large part of the night not actually flying).

For hibernation, they normally choose somewhere that is undisturbed and cool.  While each species has different tolerance levels, many can survive in temperatures below freezing by regulating their metabolic processes and by huddling up (they actually move around, even in torpor).  That said, - 4 degrees does seem to be taking things a bit far ...[;-)] - but, then again, I'm  not a bat [:)].

It may, of course, be that their winter roost has been destroyed or altered in some way since last winter.

Go here for more info http://www.bats.org.uk/pages/bat_roosts.html.  If you want more info, I have a friend who works at the Trust who may be able help.

As I'm sure you know, it's important to not disturb them.  Waking up from hibernation is very energy demanding, energy that they may not be able to replace if there's no food about.

All bat species are protected throughout Europe.  All species are in serious decline, largely due to changes in agricultural practice and destruction of roost sites.

HTH

Craig

[ventodue]

Thinking about this a bit more - you see, I like bats, me - I think your little furry friends may indeed have a problem ...

When I wrote that bats chose cool places to hibernate, that was only part of the story.  What they really seek out is cool places where the temperature doesn't alter a lot - caves and the inside of old treees, for example.  That way, they avoid being stimulated out of hibernation by a few warm days.

So this doesn't really fit with the fact that they're behind your shutters where the temperature will alter a fair bit.  Bats are also very 'site-faithful', tending to use the same sites over many generations (which is one of the reasons why they are very vulnerable to the kind of drastic changes that humans tend to effect).

So, unfortunately, I suspect an old tree has been cut down, or someone has blocked up the entry holes to their hibernation site, or the site has otherwise been destroyed or modified.  But I've been wrong before, so could well be again! [:D]

Do post a few updates during the course of the winter, if you can.

Cheers

Craig

[JohnRoss]

Ok Craig. Well my concern would be if they were ill and that might raise issues for our cat and us. Of course I have concern for the bats themselves and am well aware of the benefit of having bats around if only for the number of mozzies a bat eats in a day. The shutters are on a South West facing wall and get full sun, if there is any, for a large part of the day. None of them have been found dead on the ground below the shutters which is good news, goodness knows how they hang on, but I will monitor the situation and report back if the situation changes.........................................JR

PS The ultra sound devices are off now as if there are any Loir left in the wall spaces they will be in hibernation too.

[chris pp]

It's not at all unusual for common pipistrelle to remain in the same place for all the year, in fact they are well known for it. Grey and Brown Long eared bats are much the same so there should be no cause for concern. Only about 15 of the 29 bat species in France will use underground cavities to over winter in France the others use houses and hollow trees.

Chris

[ventodue]

Ah, ha - thanks, Chris, that's good to hear [:D]

I wasn't sure about Pips, but I had noticed that BCT draws this distinction between summer and winter sites (http://www.bats.org.uk/pages/how_and_when_do_bats_use_buildings_.html)

"Pipistrelle species

Both Common and Soprano pipistrelle are crevice dwellers that use many features on and in a building but relatively rarely enter the roof void. Features used in summer include soffits, fascias, barge-boards, weather boarding, between roof felt/membrane and tiles/slates, around window frames, in cavity walls, under hanging tiles and lead flashing. In winter pipistrelle species may use cavity walls or crevices deep in solid walls.

I've also found this on the site of the School of Biological Sciences, University of Bristol. (http://www.bio.bris.ac.uk/research/bats/britishbats/batpages/sopranopipi.htm#Life).  Given the present weather conditions, I particularly like, "Relatively insensitive to cold" [:)]

 "(Pipistrelle) Roost Sites and Patterns

• Summer roosts: in cracks and crevices in new and old buildings, behind panelling, shutters and eaves. Also found in bat boxes and trees.

• Winter roosts: trees, buildings. Exposed groups in crevices in walls and stonework. Rarely underground. Relatively insensitive to cold.

• Soprano pipistrelle roosts in houses are often unwanted. Lourenco and Palmeirim (2004) investigated the possibility of providing Mediterranean populations of soprano pipistrelles with bat boxes of suitable temperatures as an alternative. Bats were found to prefer the warmest regions in roosts, unless they were 40°C or greater. Black boxes were found to be at the correct temperature more often than white or grey boxes. However, bats left black boxes if ambient temperatures were particularly high.

• Females are found in nursery roosts of 25-50 individuals from April which they may share with Nathusius' pipistrelle.

• Barlow and Jones (1999) found that soprano pipistrelle nursery roosts were significantly larger than common pipistrelle nursery roosts.

• Males occupy territories year-round and defend them during the mating season when special social calls are emitted and the bats smell strongly of musk.

[ventodue]

[quote user="JohnRoss"]

Well my concern would be if they were ill and that might raise issues for our cat and us[/quote]

Hi JR,

Don't be too concerned about bats and rabies.  This from the BCT:

1.      Bats and Rabies

Some bats in Europe carry a rabies virus called European Bat Lyssavirus (EBLV).  EBLV is not the classical rabies which is usually associated with dogs; classical rabies has never been recorded in a native European bat species.

Bats are quite docile and will avoid contact with humans. This means that as long as you don't handle bats, you do not need to worry about bats and rabies. The rabies virus is passed on via a bite or scratch from an infected animal, or from its saliva coming into contact with your mucous membranes (your eyes, mouth or nose). If you do need to handle a grounded or injured bat, always wear gloves to avoid getting bitten.

 

[quote user="JohnRoss"]

... and am well aware of the benefit of having bats around if only for the number of mozzies a bat eats in a day. [/quote]

Well, in that case, I won't let on that, according to Bristol University, pipistrelles' main prey is non-biting midges (Chironomidae) ..

Woops! I just did ...

[chris pp]

All good stuff Craig.[:D]

A note of caution to John - bats will frequently remain hooked in place when dead but please don't touch them to find out, just leave them be. Although this is not guaranteed to happen, pipistrelles will often come out to hunt a few moths both before and after dusk on milder winter days.

Chris

[JohnRoss]

Ok folks and thanks. I don't want to keep looking at them in case it disturbs them but I am not sure if they are pipistrelles as their colour is not as brown as photos on the web show. A sort of uniform grey brown I would say. It just strikes me as strange that they have not gone somewhere else this year as they have for the last seven winters but maybe their Winter home is no more as has been suggested. I have no concerns about being bitten by a bat but our cat did catch one last Summer and is in close contact with us all the time. I rescued the bat, very carefully, and after a short period of apparent shock it recovered and disappeared. The time taken for rabies to appear is normally just a few weeks after a bite but there have been a few cases of a delay of up to one year before symptoms appear with cats. I did post about this at the time: http://www.completefrance.com/cs/forums/1345803/ShowPost.aspx  ..................................JR

PS I remember a reply from Chris at that time in another place which was reassuring and I will not disturb them further. However if they do not reanimate next Spring and are all dead I will seek futher advice as this would be significant I think. If anything happens sooner than that I will post about it.

[ventodue]

Hi JR,

Your comments on the rabies thing have inspired me to look a bit further (which is one of the things I like about forums like this: they can lead you into all sort of curious byways and backwaters).

Incidence of rabies in UK bats is reported as being very low, altho' it is generally held to be higher in European populations (I don't know what the evidence for this is).  In the UK, it seems to be mostly confined to Daubenton's bat (I wonder why?), with "about 2%" of the population having been found with the virus or its antibodies.  Pipistrelles, on the other hand, you'll be glad to hear [:)] have, to date, a 100% clean bill of health.

Go here for more info:

http://www.defra.gov.uk/animalh/diseases/notifiable/rabies/bat-research.htm.

http://www.defra.gov.uk/animalh/diseases/notifiable/rabies/handlers.htm

I remember the case of the field worker in the UK who died of bat-contracted rabies and I seem to recall that he refused any treatment, a point which is made in the papers mentioned above in relation to the 5 other rabies deaths in Europe.  All the UK bat handlers that I know are, of course, aware of the problem, but generally reckon the bigger risk comes from falling off any ladder they might be using in the course of their work [:D]

(I notice that Eurobats, the secretariat for bat conservation in Europe, considered whether it was worth setting up a working group to look into the issue - and decided not to).

Cheers

Craig

 

[chris pp]

It France it's almost totally Serotine bats that carry rabies and they are very dark in colour, almost black. The subject is always part of the annual bat conference in France and really is to be considered of low risk and little concern. Although the recommendation is always to wear gloves, no one that I know does, but that's always the same isn't it?

If you find that they are dead in the spring - let me know and I will see what I can do to have them analysed, but again it should be no cause for concern, bats as with all creatures die all the time from a variety of causes.

As far as I know only two humans have died from bat rabies in Europe in about forty years and one of them was a "handler".

Can you say roughly what size the bats are John?

Chris

[ventodue]

[quote user="chris pp"]

It France it's almost totally Serotine bats that carry rabies ...[/quote]

Thanks Chris.  So, Daubenton's in UK and Serotines in France ... any idea why?

(Btw: To put European rabies in context: According to the WHO, "There are an estimated 55,000 human deaths annually from rabies worldwide, with about 31,000 in Asia, and 24,000 in Africa".)

[JohnRoss]

Very difficult to say Chris without disturbing them further but at a guess I would say between 5cm and  8cm body length. Colour is brown and not black with a darker streak along the wing/front leg edge. If one drops out from behind the shutters dead I will photograph and send to you..........................................JR