Bats and agri-environment schemes

Setting up a detector in the field to monitor bats. © Niamh McHugh/GWCT

BACKGROUND

Several European bat species declined during the 20th century owing to many factors including the loss of roost and feeding sites through agricultural intensification. Bat roosts in England are protected by law, but feeding sites are not, making them susceptible to land use change. English agri-environment schemes (AES) represent approximately 14% of agricultural land in the UK and, although they do not specifically target mammals, many are designed to increase invertebrate food resources. They may therefore represent important local foraging patches for bats. Across Europe agri-environment schemes (AES) have been introduced which attempt to counteract biodiversity losses relating to agricultural intensification. However, the potential benefits of AES to non-target groups such as bats are unclear. The AgriBats project aimed to determine how AES habitats are used and can be best managed to benefit a range of bat species. In our study, we assessed how the vegetative characteristics of four commonly employed AES habitat types (grass margins, wildflower margins, wild bird seed mixture plots and pollen and nectar plots) influenced the occurrence and activity of bats.

Surveys were conducted on 48 AES habitat plots across 15 farms. Each plot was surveyed for nine nights between 12 April and 1 September 2017 using passive real-time bat detectors, resulting in 432 nights of recordings being collected over the project. After data checking 9,154 recordings of bats were available for analysis representing six species and a further two bat genera (see Table 1). Common pipistrelle were recorded most frequently accounting for 71% of recordings, soprano pipistrelle and barbastelle were also recorded relatively frequently, representing 10% and 6% of recordings respectively. Therefore, in this summary, we focus on relationships between these three bat species and AES.

The vegetative characteristics of AES habitats were assessed in five 0.5-m² quadrats, spaced 10 metres (m) apart, centred around the bat detector. Grass, broad-leaved plant and bare ground coverage was estimated in each quadrat, and counts of the number of ground flora species and the number of individual flowering plants present within quadrats were made. The adjacent field boundary height was estimated to the nearest 0.5m and averaged across five points. The number of trees present was also counted and distance measured to the nearest woodland, as the crow flies.

The importance of AES vegetation characteristics varied between bat species. Cover of flowering plants was positively correlated with the occurrence of common pipistrelle. Soprano pipistrelle and barbastelle activity increased with plant diversity within plots, and barbastelle activity showed a further positive correlation with flowering plant abundance. Common pipistrelle was most influenced by field boundary features and its activity was positively correlated with boundary height and the number of trees present. Barbastelle activity was also positively related to boundary

TABLE 1

Recorded bat species and the number of validated recordings. Passive real-time bat detectors recorded bat activity over nine nights in 48 fields in south-west England in 2017

Common name Number of validated recordings Percentage

Common pipistrelle 6,540 71.4

Soprano pipistrelle 901

9.8 Nathusius’ pipistrelle 75 0.8 Barbastelle 559 6.1 Serotine 358 3.9 Common noctule 106 1.2 Myotis species 268 2.9 Plecotus species 62 0.7 Unidentified 285 3.1

Total 9,154

height. Negative relationships were also identified between barbastelle occurrence and distance to the nearest woodland.

The importance of specific AES vegetation characteristics varied between bat species, but common pipistrelle, soprano pipistrelle and barbastelle demonstrated significant positive relationships with the cover of flowering plants, plant diversity or flowering plant abundance. These habitat characteristics best describe pollen and nectar plots and wildflower margins, both of which are designed to benefit invertebrates. Furthermore, soprano pipistrelle and barbastelle bats were associated with woodland proximity and may therefore benefit from floristically diverse foraging sites, which are attractive to bat invertebrate prey, if they are in close proximity to potential roost sites. Common pipistrelle were also attracted to AES habitat patches with a high coverage of flowering plants and were also more abundant if such habitats were located along tall field boundaries with trees, which probably provided shelter for their prey. Therefore, if AES habitats are to be used to help conserve bats, consideration should be given to the spatial arrangement of floristically rich and diverse AES habitats in relation to fixed landscape features.

For more details, see the published paper: McHugh, NM, Bown, BL, Hemsley, JA & Holland, JM 2019. Relationships between agri-environment scheme habitat characteristics and insectivorous bats on arable farmland. Basic and Applied Ecology 40, 55-66. KEY FINDINGS

Soprano pipistrelle and barbastelle bats were more abundant near woodland, possibly because it was being used for roosting. They also favoured habitat characteristics which best describe pollen and nectar plots and wildflower margins.

Common pipistrelles were attracted to agri-environment scheme (AES) habitats with high flower coverage and also preferred it when these habitats were adjacent to field boundaries with trees.

The spatial arrangement of flower-rich AES habitats in relation to landscape features, should be considered if AES habitats are to be used to benefit bat conservation.

Niamh McHugh Belinda Bown Jade Hemsley John Holland

ACKNOWLEDGEMENTS

We are grateful to the landowners who allowed us to conduct fieldwork and to Anna Forbes and Sophie Potter for their assistance in data collection. This work was supported by the Heritage Lottery Fund, Natural England, the Hamamelis Trust, Chapman Charitable Trust, Wixamtree Trust and the Mercer’s Company.