Farmland left to nature makes bats at home

Farmland left to nature makes bats at home

European bat species have been in decline due to a loss of feeding sites and roosts – where bats settle to rest during the day. In the UK, bat roosts are protected by legislation, but feeding sites are not. This makes European bat species in the UK vulnerable to land use change and agricultural activity, whether it be the use of fields for livestock grazing or the growing of crops.

Bats are incredibly important to the ecosystem, as some plants depend on bats to pollinate their flowers or spread their seeds, and certain bats help get rid of pests by eating insects. In the UK, some bats are called ‘indicator species’ because any changes they show in the behaviour reflects a noteworthy change in an environment’s biodiversity.

Pipistrelle bats in Britain

The most common, and the smallest type of bat in Britain are the pipistrelles, comprising three species: the common, soprano and Nathusius’ pipistrelles. Recognisable with their reddish-brown tiny bodies and black-brown ears, pipistrelle bats are protected in the UK under the Wildlife and Countryside Act (1981) and by the European Habitats Directive.

These bats are sadly in decline, so it is important to understand what can be done in the natural environment to support their populations. Over a quarter of land in the UK is arable farmland, and agriculture in the United Kingdom uses nearly 70% of the country's land area, so scientists are interested in how agriculture impacts bat feeding and roosting sites.

Agri-environment schemes have provided financial incentives to farmers and land-owners to put aside parts of their land to support biodiversity, enhance the landscape and improve the quality of the water, air and soil around. When farmland is left to nature, wildflowers and rich meadows can grow, which attract diverse wildlife like birds, insects and bats.

Agri-environment schemes aid bats

In a 2018 study by McHugh et al published in Aspects of Applied Biology, researchers realized the importance of agri-environment schemes in providing foraging habitats for pipistrelle bats. Specifically, the scientists were interested to find out which agri-environment management option had the greatest effect on the activity of the UK’s three pipistrelle species. To find out, they surveyed pipistrelle activity at 15 farms across Hampshire and Dorset having at least three of the following: grass margins, wildflower margins, wild bird seed mixture plots, pollen and nectar plots.

The team used bat detectors to record the presence of bat echolocation calls, which told the scientists how many were there, and about their behaviour. Detectors were placed along 48 field boundaries and acoustic sampling took place at each location on three consecutive nights, providing 144 nights of pipistrelle recordings. The recordings were sampled using software and data was later analysed through computer models. 

After 144 nights of data collection, 7213 bat recordings were produced. After filtering, 1152 recordings were omitted, and the remaining 4548 identified common pipistrelle, 521 as soprano pipistrelle and 73 as Nathusius’ pipistrelle.

Variety key to the success of bat species

The fields with pollen, nectar and wildflower margins showed more activity from the common and soprano pipistrelles, which were not just used as commuting corridors. By contrast, these grass margins were not favoured by the Nathusius’ pipistrelles who preferred wooded shelter belts, and to be near chironomids – a type of non-biting midge they commonly prey on.

As shown in this study, we can see that a variety of habitats are needed under the agri-environment scheme to allow different species of pipistrelle bats to settle, roost and feed safely. So far, agri-environment scheme managers have mainly focused on the benefits to birds, insects and plants. Researchers emphasise it is also important to consider how pipistrelle bats benefit from the enhanced biodiversity resulting from these schemes, particularly where there is more insect prey available.

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