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Friday, 24 March 2017

'Bats, dormice and water voles', a talk by Louise Woolley on 14th March
Chris Shields (rspb-images.com)

'Bats, dormice and water voles', a talk by Louise Woolley on 14th March

Last time I wrote up an indoor meeting it was a two-part talk, but this time it is a three-parter. Next time, who knows how many parts! Carolyn invited Louise Woolley to talk about the monitoring of dormice that she is doing for the RSPB and Woodland Trust. Fortunately Louise thought that we would also like to hear about bats, which are her main interest, and water voles, which she has been involved in reintroducing to the Axe valley and this proved to be an inspired choice for a talk

Louise started by de-bunking several myths about bats: they are blind, suck your blood, get stuck in your hair, carry diseases, gnaw wires and scurry around in your loft. It turns out that these are all untrue, or at least grossly exaggerated. In Devon, we are fortunate to have 16 of the 18 species of bat that are native to Britain. Three species of Pipistrelle are amongst the most common. The Greater Horseshoe Bat has declined massively in recent years, but Devon is still a stronghold. The rarest British bat is the Greater Mouse-eared Bat - there is only one known individual!

Overall bat numbers declined by 70% between 1978 and 1993, mainly because of the use of pesticides and because roosting spaces in houses have been sealed up. Many bats would have originally lived in crevices in trees, but now they are highly dependent on buildings. Other bats roost in caves, and some in churches. It is now illegal to destroy or disturb bat roosts. Bats gather in swarms to mate in autumn, hibernate through winter, and then give birth in summer (after delayed implantation of the fertilized egg). Over the year, they use several different types of roosts, including for hibernation, maternity, summer roosting and resting during feeding flights.

There are bats on several nearby nature reserves, including Aylesbeare Common, Venn Ottery Common and Fire Beacon Hill, and several local organizations that work together to help conserve bats.

Dormice are an iconic species of Devon, and locally reasonably common - Devon hedge banks are just perfect for them. Although Hazel Dormice are widespread across roughly the southern half of Europe, they have declined a lot due to the loss (and fragmentation) of hedges and woodland. They live at low population densities and do not breed as prolifically as other small mammals. Dormice often use nest boxes, but apparently do not significantly compete with birds.

A national Dormouse monitoring programme has been running for 25 years, and has shown that the population has declined by 30% since 2000. Locally, 2016 seems to have been a bad year across Devon; the population at Aylesbeare is quite stable, but it has declined in other local reserves.
Water Voles are a species in rapid decline. There are none on local RSPB reserves, but there are some on the Axe Wetlands. Water Voles are the largest species of vole, the size of a rat - but they are not rats! They originally lived on land, and they still do in much of Europe, but in Britain they are riparian - living on river banks, around ponds and in reed beds. They use very similar habitat to Moorhens.

They have about 5 litters a year, with up to 7 in each litter, but they are heavily predated and so life is very short. Their main natural predators are foxes, stoats and herons. But pollution from organochlorine chemicals and the release of American mink have accelerated their decline. Although mink farming was banned in 2003, that led to a further release of mink. A range of conservation measures can help the Water Voles, including coppicing along river banks, and fencing banks from cattle. Himalayan Balsam is also a problem for them.

Before Water Voles can be reintroduced mink need to be monitored using mink rafts, and then removed. Water Voles were reintroduced onto the river Tale in 2006, initially against the advice of the authorities. Following a change of heart, a Water Vole Recovery project was started in 2009, entailing the release of Water Voles in the Axe Valley. Despite dwindling funding for the project, they are now established 20km downstream from the original population.

All in all Louise gave us a very interesting evening, hearing about some of the most iconic small mammals that live in Devon. It reminded us that we need to think about the range of wildlife that makes up the ecosystem - not just birds.

Richard Swinbank