You wouldn't think it would be exciting to keep finding poo on your steps - but I was thrilled, because it meant that bats had moved in. But why is that such good news? Here are 7 things you might be interested to know about bats in a Bordeaux vineyard:
1. There are 22 known species of 'chauve-souris' (bat) in Gironde, the area around Bordeaux, and of these, a recent study recorded 10 in and around the vines. Given how hard they are to spot when resting and how fast they move when flying, it is through the different high frequency ultrasonic waves they emit for echolocation that we (or rather experts) can distinguish the different species.
2. Bats are the only flying mammal in Europe and whilst they use the echolocation to navigate and find food at night, they certainly aren’t blind. In fact, they can see pretty well and use their eyes during the light of day and their good hearing at night. Their vision is tuned to low-light conditions of dawn and dusk and overall, it is better than a human's at those times of day.
3. Most species of bats are small. The most common species is the Common Pipistrelle or 'Pipistrelle Commune'*, and the one we know we have here at Château George 7 - measuring just 4cm but with a wingspan of around 20cm and weighing on average 5-6g. Yes 5g!!! These tiny creatures can eat up to 600 insects per night – coming out at dusk to forage after sleeping during the day.
4. Recent Bordeaux studies** have proven the theory that bats have a key role in the vineyards. They keep down pests such as the European grape moth (there are 3 main species) who are prolific as that reproduce over several generations from Spring to harvest time and damage the grapes in quantity and quality. We want to avoid all pesticides so we try and keep the moths at bay by confusing the males with female pheromones to hinder breeding (see blog on Confusion Sexuelle ). Bats are natural predators of all the grape moth species who mainly fly at dusk, when bats are also foraging, so they are a welcome addition to the team. Importantly too, the continued use of pesticides promotes pest resistance and the possible emergence of other pests and diseases so the presence of bats can break that cycle.
5. The more grass, wild flowers, hedges and cover crops that there are between and around the vines, then the more bats are present and active. Again, this has been proven and so even if the grape moths are not there, bats are attracted by other types of insects. Biodiversity provides food but also places to set up home. And nearby water is also a great pull for bats to set up residence, even if it is just a small area, because of the insects (ie food) that water attracts.
6. Bats don’t do any damage and don’t build nests but can slip into really small crevices and cracks in buildings or trees. Bat boxes are also successful if put in the right place (not in a tree to avoid predators getting close, oriented towards the sun for warmth and about 5m up as they need height to drop down before catching flight). They are quite touchy though, and if disturbed, will up and move. All species in France are protected (since the 1976 law) so it is illegal not only to kill them but also to capture or handle them. They only give birth to one young at a time, once per year in early Summer. They suckle the young then mate in Autumn before hibernating until Spring.
7. TMI Alert: Their poo (known as 'guano') is often mistaken for mouse droppings as they look so similar. You will usually find it next to a wall or at the base of a structure or tree and if you really want to know if it is from a bat, crumble it in your fingers and you will see the insect remains.
Restoring balance in the vineyard is often said, but bats moving in is real evidence of it happening. Through planting trees, hedgerows and cover crops and letting grass grow, we are encouraging a more diverse insect life, which has attracted bats that are feasting on unwanted vine pests. I am looking forward to the warmer days when they will be flying around the vines of Château George 7 again, as I sit and enjoy the sunset while watching everyday sustainability in action.
*The other 4 most common species found in vines in Gironde are: Pipistrelle de Kuhl, l’Oreillard Gris, l’Oreillard Roux and Petit Rhinolphe.
** Get in touch if you would like the details of the research paper.