Figure 1 . Map of the surveyed nestboxes in Basildon Park House
(UK) showing the main habitat types and the historical occupancy by
hazel dormice M. avellanarius of 45 sampled nestboxes. Thewoodland site is on the north boundary, with the hedgelinein the South on the southern boundary, adjacent to arable land. Top left
inset shows the study area location in the UK.
In 2013, 144 nestboxes were erected at two different sites within BPH:
78 were located in the woodland site and 66 in thehedgeline site (Fig. 1). Within the woodland site, mature
beech (Fagus sylvatica ) is dominant in the tree canopy layer, ash
(Fraxinus excelsior ) and oak (Quercus spp.) frequent, and
sweet chestnut and field elm occasional. Hawthorn (C. monogyna )
and coppiced hazel (C. avellana ) are dominant in the understorey
layer, with holly and young sycamore frequent, and other species such as
field maple, whitebeam and rowan occasional. Bramble (Rubus
fruticosus agg.) and honeysuckle (L. periclymenum ) are abundant
in both the understorey and field layer. In the hedgeline site,
most boxes are situated on the boundary between woodland and arable land
(in 2021 the crop was rapeseed, Brassica napus ), amongst what
used to be a hedge, but is now a line of mature scrub. The main tree
canopy species here are oak (Quercus spp.), lime and beech which
are frequent, although there are some sections where there are no canopy
tree species present. In the understorey cherry plum (Prunus
cerasifera ) is dominant, with spindle and young oaks occasional. The
boxes within hedgeline site also extend northwards into a mature
woodland, where the dominant tree canopy species are mature beech and
oak, with hazel dominant in the understorey, and hawthorn and and young
sycamore frequent. Bramble is dominant in the understorey and field
layer species.
All nestboxes at BPH have been regularly monitored by the Berkshire
Mammal Group since 2017 as part of the National Dormouse Monitoring
Programme (NDMP). No monitoring occurred between 2013 and 2016. As part
of the NDMP systematic survey methods, nestboxes are typically surveyed
monthly (between the 15th and 25thof each month) from May-September. At BPH the Berkshire Mammal Group
check the boxes up to four times a year, dependent on the availability
of a licensee. Routine cleaning takes place over winter. During each
survey, nestboxes are recorded as empty or occupied by hazel dormice if
individual dormice are present, or there is a new nest or an old nest
with signs of recent occupation e.g. faeces (Panchetti et al. 2007).
Individual dormice are sexed, classified within an age class, weighed,
and assessed for breeding status. Using the full survey records between
2017 and 2020 and the first season survey of 2021, we classified
nestboxes as historically occupied (occupied at least once since
2017) or unoccupied (not occupied since 2017) and selected 13occupied nestboxes at the woodland site and all 8occupied nestboxes at the hedgeline site (total 21occupied nestboxes). For the woodland site we selected all
boxes occupied frequently (in more than one survey) and recently
(occupied at least once in the last three years). If two boxes in close
proximity (<10m) met these criteria, we randomly selected one
of them to avoid replicating microhabitat data. We also selected 24
historically unoccupied nestboxes (12 from each site) using the
SelectRandomByPercent function in ARCGIS 10.5.1 excluding any nestboxes
within 10m of selected occupied nestboxes. If two selectedunoccupied nestboxes were in close proximity (<10m) we
located an alternative pair in the area at least 10m apart.