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Loss of linear features

Linear landscape features, such as hedgerows and tree lines, are important habitats for bats, providing flight paths between roosts and foraging sites and as foraging habitats (e.g. Verboom & Huitema 1997, Oakeley & Jones 1998, Russ & Montgomery 2002). Common and soprano pipistrelle, Daubenton’s bat, Natterer’s bat, greater horseshoe bat, lesser horseshoe bat, brown long-eared bat and serotine all forage or commute along linear features (e.g. Limpens & Kapteyn 1991, Downs & Racey 2006). However, the dependency on linear features in the landscape varies between species: while smaller species such as Daubenton’s bat and common pipistrelle most commonly choose to avoid open areas by following linear features quite closely, larger species such as noctule will cross open areas more often and intermediate species such as serotine do both (Limpens & Kapteyn 1991, Verboom & Huitema 1997).

Loss of hedgerows

Widespread hedgerow removal occured between the 1960s and early 1990s to allow improvements to farming efficiency, stock-proofing and weed control (Macdonald & Johnson 2000). Although hedgerow loss slowed in the 1990s and agri-environment schemes encourage their reinstatement and better management, there is continued severance of these important commuting and foraging habitats due to increasing urbanisation and new infrastructure development, of for example roads. Loss of hedgerows is likely to affect bats by reducing access to suitable foraging habitats or isolating populations (e.g. Russ & Montgomery 2002).

Hedgerow management

As well as hedgerow removal, there has also been an increasing trend to manage hedgerows more intensively and reduce their height and width, decreasing the available habitat for wildlife (Newton 2004).

There is some evidence that this switch to intensively managing hedgerows has negative impacts on bats. Russ et al. (2003) recorded low pipistrelle activity in areas of improved grassland with cut hedgerows less than 0.5m high, while Russ and Montgomery (2002) found that hedgerows were generally avoided in Northern Ireland and suggest that it is due to the predominance of mechanically cut, box-shaped hedgerows.

There is also evidence that bats prefer large, bushy hedgerows which results from less intensive management: in Holland for example, Limpens and Kapteyn (1991) found that linear elements such as hedgerows of less than 1m in height were rarely used; in England greater horseshoe bats in particular prefer tall and wide hedgerows (2-5m in height and width) (Duverge & Jones 2003) and one study (Bates 2010) found that activity of several species (including Myotis species, serotine and Nyctalus species) was higher at large hedgerows than small hedgerows on farms. Although pipistrelles are strongly associated with hedgerows, analysis of NBMP data has shown that the size of the hedgerows seems to be less important for common and soprano pipistrelle (Boughey et al. 2011).

The general preference for larger hedgerows may be due to the windbreak effect of bigger hedges and a higher abundance of insects on the sheltered side of the hedge. Currently, agri-environment schemes promote enhanced hedgerow management which may provide benefits for bats.

 

References

Bates FS (2010) The impact of hedgerow management on organic and conventional farms on small mammals, bats and their insect prey. PhD thesis, University of Bristol, UK.

Boughey KL, Lake IR, Haysom KA & Dolman PM (2011). Improving the biodiversity benefits of hedgerows: How physical characteristics and the proximity of foraging habitat affect the use of linear features by bats. Biological Conservation, 144: 1790–1798

Downs NC, Racey PA (2006) The use by bats of habitat features in mixed farmland in Scotland. Acta Chiropterologica 8: 169-185.

Duverge PL, Jones G (2003) Use of farmland habitats by greater horseshoe bats. In Tattersall, F, Manley, W (eds) Conservation and Conflict. Mammals and Farming in Britain, 64-81. The Linnean Society, London.

Limpens HJGA, Kapteyn K (1991) Bats, their behaviour and linear landscape elements. Myotis 29: 39-48.

Macdonald DW, Johnson PJ (2000) Farmers and the custody of the countryside: trends in loss and conservation of non-productive habitats 1981-1998. Biological Conservation 94: 221-234.

Newton I (2004) The recent declines of farmland bird populations in Britain: an appraisal of causal factors and conservation actions. Ibis 146: 579-600.

Oakeley, SF, Jones, G (1998) Habitat around maternity roosts of the 55 kHz phonic type of pipistrelle bats (Pipistrellus pipistrellus). Journal of Zoology 245: 222-228.

Russ JM, Montgomery WI (2002) Habitat associations of bats in Northern Ireland: implications for conservation. Biological Conservation 108: 49-58.

Russ JM, Briffa M, Montgomery WI (2003) Seasonal patterns in activity and habitat use by bats (Pipistrellus spp. and Nyctalus leisleri) in Northern Ireland, determined using a driven transect. Journal of Zoology 259: 289-299.

Verboom B, Huitema H (1997) The importance of linear landscape elements for the pipistrelle Pipistrellus pipistrellus and the serotine bat Eptesicus serotinus. Landscape Ecology 12: 117-125.

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