Geoffroy's bat, (Myotis emarginatus), a chance encounter in the south Vienne dept (86).

 

Being both a bit of a naturalist and a bee keeper people sometimes contact me to remove honey bee colonies that have been constructed between closed shutters and the window. This is an ideal space and a fairly common occurrence in France with second homes that are left empty during the swarming season and only discovered when the owners return to their house or when someone they know or employ takes a look at the house.

A few years ago, August 2021 to be precise, one of the houses I was called to was in Charroux, (86250) by a neighbour of an empty property that was a keyholder, where the following day I proceeded to dismantle the comb and re house the bees in a ruchette, (small hive). During a pause in proceedings the neighbour invited me for a coffee and we then took a walk though his land chatting about wildlife and conservation in general. During the course of this chatting he mentioned that they had a large number of bats every year in their outbuildings which immediately grabbed my interest. Of course it's not unusual to have a number of bats in a roof or an outbuilding in France but a large number clustered close together will invariably be a Maternity colony or nursery. We went to look and there were no bats present, but this would be expected in late summer as the bats that formed the nursery would have dispersed to individual hang outs, however there were some photos that clearly showed an important nursery. Having taken the property owners details and asked if would be OK to inform Vienne Nature, (the responsible structure for overseeing bat populations in the Vienne departement), I packed up my gear from collecting the bees and left.

Greater Horseshoe bat and Geoffroys bat

At around this time the ongoing health situation with my wife took a serious downturn and everything took second place to my caring for her and I forgot about the bat nursery until after her death in July 2023. It was following this that I popped in to the offices of Vienne Nature and finally mentioned the bats, passing on the contact details to Samuel Ducept, (chargé d'études entomologie), and Alice Chéron, (chargée d’études chiroptères-faune). Following this Alice made contact with the owner of the property and a first visit took place that confirmed the presence of 494 Geoffroy's bat, (Myotis emarginatus), making this by far the largest and most important of the 3 known nursery sites for this bat in the Vienne. In June 2024 Alice Chéron visited the site for a second time and it turned out that two species of bat were using the same building as a nursery, the second species being 87 Greater Horseshoe bats, (Rhinolophus ferrumequinum), in total making this the third most important known nursery for this species in the Vienne. It's quite common for these two species of bat to share the same nursery structure and following the discovery of this important site it is proposed by Vienne nature to visit and monitor the bats in June each year.

Counting Geoffroys bats

A maternity colony which is known as a mise-bas in French refers to a temporary association of reproductive female bats for giving birth to, nursing, and weaning their pups. The colonies are initiated by pregnant bats that arrive in late spring but pregnancy in bats is another of natures remarkable affairs given that actual copulation usually occurs in the previous year prior to hibernation involving delayed ovulation where the sperm is stored in the bats uterus and oviduct, or sperm storage which is where sperm is stored in either the caudal part of the epididymis or the vas deferens, (sperm duct), of the male or after copulation in the uterus and oviduct of the female. Whether in the epididymis or uterus, the bat sperm can stay alive and healthy for months until it is required.

The number of bats in a nursery can vary substantially, in part depending on which species of bat they are but equally there can be a large variation within a species. With Geoffroy's bats it can be as few as 10 or exceptionally as many as 1,000. Somewhat less for Greater Horseshoe bats with a maximum of 600, usually much less tending to be between 30 and 200.

In Europe as a whole bats have suffered serious declines in their numbers and as such they are fully protected at both the European and National level. The positive news is that in the Vienne both of these species have populations that have shown some small growth in numbers for the period 1995 to 2015. This is based on winter surveys of their known hibernation zones and according to the Vienne departements “red list” Greater horseshoe bats are listed as “Vulnerable”and Geoffroy's bats are listed as “Least concern”. Overall in France they are both listed as Least concern but that shouldn't be seen as a reason for complacency and it is of utmost importance to monitor populations and protect any nurseries.

A few brief facts:

Greater horseshoe bat is Grand rhinolophe in French and Geoffroy's bat is Murin à oreilles échancrées hence the alternative name for this bat in English of Notch eared bat.

Greater horseshoe bats mainly eat chafers, dung beetles, noctuid moths, craneflies and caddis flies which they take from the ground or from the air when flying low along hedgerows, woodland edges and over water.

Geoffroy's bats preferred prey are either flightless, such as spiders or flies of all types that don't fly at night and can be taken from their resting places in scrubland, grazing pastures and inside animal sheds and shelters.

In both cases, as it is with all bats in France, large quantities of insects will be consumed in one night, well in excess of 1,000 when it comes to smaller insects.

Both species hibernate underground in disused cellars, caves, old underground mines and excavations.

If you think you have a nursery or would like to take part in winter bat surveys you can contact your local authorised bat group or contact me via my Facebook page if you need any help with this.

Chris Luck.