Wednesday, 19 February 2014

Bats and mushroom growing underground in France.

One thing I've learnt is that when you get out and about you never know what that day will bring and that was certainly the case again the other week when I went to do a bit of underground Bat recording organised by Samuel Ducept and Miguel Gailledrat of Vienne Nature. We met at the bureau at 9am which is early enough for me in winter and as soon as everyone was present set of in two vehicles, 5 people in each to go our separate ways for the day.

I must mention that for some unknown reason it seems that it’s mainly females in France that are “into” bats and Saturday was no exception. Other than Sam and Miguel I was the only male the other 7 being “girls”, (any female under about 35 or possibly 40 is a girl to me these days).

We were going to try and research some underground cavities that either hadn't been looked at before or hadn't been researched for several years. These are all old workings, principally underground quarries in the first instance to provide the limestone that was used to build the châteaus and houses and most were then used for other functions, storing food such as cheese if part of a large property or used as champignonnières – commercial mushroom production. This was the principle means of commercial mushroom production in France during the 19th century until the middle of the 20th century thanks to the ideal conditions they provided, a more or less constant temperature, easy to regulate air flow and a good level of humidity. The process is quite complex and rather than make gross errors I have linked to a good site below in French with some interesting old photos but all methods required the use of containers filled with compost made with a mix of manure and straw plus lime.

Click on photos to enlarge.

These old underground caves or cavities are always on private land, often some distance from a road and sadly many have become blocked or overgrown. Of course overgrown or even partially blocked isn't necessarily a problem for over wintering bats providing they still have reasonable access but it obviously reduces the ability to record numbers effectively. Inevitably for us it meant drawing several blanks which is always disappointing however we did manage to find and gain access to several caves of varying sizes over the course of the day even when it meant overcoming a few obstacles.

It’s probably not a surprise to anyone that these caves are used by all manner of other species besides bats and in two caves there was the unmistakable and all pervasive smell of fox and even a brief glimpse of one as it ran away from our lights. Large numbers of Peacock butterflies and literally hundreds if not thousands of Herald moths Scoliopteryx libatrix hibernating all over surfaces of one cave and even a small cluster of Eristalis tenax hoverflies in a shallow hole in the rock face. There are always small clouds of lethargic mosquitoes and other midges waiting for spring and even quite large numbers of chocolate coloured slugs in one cave.

Not all bats favour caves to over winter with many species using houses, buildings or cavities in forest trees. The common pipistrelle Pipistrellus pipistrellus, one of the commoner bats prefers buildings and when found in a cave it will usually be near the entrance as will be Barbastelle Barbastalla barbastellus. The Large and Small Horseshoe bats are to be more likely found far from the entrance in the warmer air where they can sometimes remain moderately active even flying around sometimes and as they are often not actually asleep greater care needs to be taken not to disturb them.

Totals for the day.

Greater Horseshoe bat    73
Lesser Horseshoe bat      12
Brown Long eared bat     5
Daubentons bats             8
Whiskered bat                42
Geoffroy's bat                23
Natterer's bat                  6
Bechstein's bat                5
Greater mouse-eared bat  33

Although there was a reasonable number of Greater Horseshoe bats they weren't in substantial groups.