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Mammal monitoring through the BBS Mammal recording was introduced to the BBS in 1995 with a view to help improve our knowledge of the distribution and population trends of some of our commoner mammals. Compared with birds, the population trends of mammals are relatively poorly known. Even though mammal recording has always been a voluntary addition to the scheme, more than 80% of BBS observers now actively look for them during their bird-count visits. Tracking Mammals Partnership The data collected by BBS observers provide important information for assessing population trends of certain mammal species. BTO is a member of the Tracking Mammals Partnership (TMP), a collaborative initiative involving 25 organisations, with varied interests in mammals. TMP aims to provide good quality trend data to guide conservation and wildlife management policy for mammals. There is also cooperation to recruit, train and support the network of volunteers who carry out the surveys. TMP has published the first major report on UK mammal population trends, assessing population change for 33 species and one subspecies, representing over 50% of land mammals in the UK. The data are being collected in a programme of 17 surveillance schemes, including the BBS, which routinely provides trend data for nine species.
UK Mammals: Species Status and Population Trends. First Report by the Tracking Mammals Partnership can be downloaded from the TMP website (www.trackingmammals.org) or can be purchased through NHBS, price £7.00. Mammal recording on BBS squares in 2006 In 2006, mammal records were received for 83% of surveyed BBS squares (2,740 squares). Table 1 shows the fifteen most frequently recorded mammal species in 2006. For easily detectable diurnal species such as Rabbit, Grey Squirrel, Brown Hare and some of the deer, the vast majority of records were for individuals seen and counted during the two counting visits. However, for other mammals, a large proportion of the records were based on field signs, dead animals and local knowledge of the species’ presence on that site. These include nocturnal or crepuscular species such as Mole, Red Fox, Badger, Hedgehog, Stoat and Weasel. In addition to those listed in Table 1, a further 32 mammal species were recorded during the survey, including (number of squares in brackets): Mountain or Irish Hare (52), Red Squirrel (44), American Mink (38), Otter (37), Common Shrew (29), Sika Deer (26), Wood Mouse (18), Pipistrelle sp. (13), Field Vole (11), Water Vole (11), Bank Vole (7), Chinese Water Deer (7), Common Seal (5), Feral Goat (5), Pygmy Shrew (5), Grey Seal (4), House Mouse (4), Harvest Mouse (2), Orkney Vole (2), Water Shrew (2), Wild Boar (2) and Barbastelle, Brown Long-eared Bat, Dormouse, Ferret, Harbour Porpoise, Lesser White-toothed Shrew, Natterer’s Bat, Noctule, Pine Marten, Polecat and Serotine on single squares. Single squares in Suffolk and Norfolk proved to be the most diverse in 2006, with nine species of mammal being seen on each during the two counts. One or more species was seen during the two bird count visits on 2,396 squares (87.3% of squares surveyed for mammals). In addition, field signs were noted, or mammals were seen on additional visits on another 146 squares (5.3%), leaving 198 surveyed squares (7.2%) where no mammals were recorded. It is very important that we continue to receive completed mammal forms or online submissions for those squares where no mammals were recorded, as these contribute just as much as mammal-rich squares to the analyses of population trends. Table 1. Occurrence of common mammal species on BBS squares in 2006
NB: The first two columns of data show the number and percentage of squares in which each mammal species was known to be present (including squares in which the species was seen and a transect count made). The next two columns show the number and percentage of squares in which each mammal species was actually seen and counted, and the final column the total number of individuals counted. Monitoring UK mammal populations using the BBS By recording the number of each mammal species seen during the BBS survey and the occurrence of species such as Red Fox and Moles from obvious signs of their presence, the BBS has the potential to monitor UK mammal populations. The occurrence of nine mammal species on BBS squares over the period 1995-2005 was adequate to allow annual indices of abundance to be calculated (Tables 2, 3 and 4). This included four species of deer (Red, Roe, Fallow and Reeves’s Muntjac), three lagomorphs (Brown Hare, Mountain/Irish Hare and Rabbit) and Grey Squirrel and Red Fox. These are all diurnal (day active) or crepuscular (active at dawn and dusk) and are relatively large in size, so their detectability is high. Data for the two herding deer species (Red and Fallow) and for six species monitored solely by indirect evidence of their presence (e.g. Stoat, Badger) are continuing to be analysed in order to produce more reliable trends. Where data are sufficient, population trends have been calculated for England, Scotland and Wales as well as for the UK overall. It has also been possible to produce trends for seven of the nine English Government Office Regions (North West, Yorkshire, East Midlands, East of England, West Midlands, South East and South West) and for four of the six Environmental zones (defined by landscape type) within Great Britain. Population trends have been calculated only for species recorded on a mean of thirty or more squares each year and for this reason, we were unable to calculate any trends for Northern Ireland, or the Government Office Regions of North East England and London. For those species too seldom detected for any indices to be calculated, the BBS can still provide information on their distribution and changes in abundance. Table 2. Changes in abundance of Rabbit, Brown Hare and Mountain/Irish Hare between 1995 and 2005.
Table conventions: the figures presented in the ’n’ columns show the mean number of squares the species was recorded in each year during 1995-2005 (excluding squares which were surveyed in only one year). The figures presented in the ‘% Chg’ columns show the percentage changes in population levels during 1995-2005, in bold where the change was significant at 95%. Cells left blank indicate that the sample size was too small in that country/region for a trend to be calculated. Rabbit Oryctolagus cuniculus. Numbers peaked in the UK in 1997 but have declined almost continuously since, albeit with a slight recovery in 2005. Overall, numbers are still significantly fewer in 2005 than compared to 1995. There has also been a significant decline in Scotland over the survey period, and within several of the English regions. The Rabbit is a widespread species across the UK. Brown Hare Lepus europaeus. There was no significant change in numbers in the UK between 1995 and 2005. Abundance has not significantly changed in Scotland or England, although there have been significant decreases in North West and South East England and significant increases in Yorkshire. Brown Hares have also declined significantly in the uplands of England and Wales. The Brown Hare is a widespread species across the UK, although scarce in Northern Ireland. Mountain or Irish Hare Lepus timidus. No significant change in numbers was detected in the UK between 1995 and 2005. Mountain/Irish Hares are primarily found in Scotland and Northern Ireland, although there is a small population in the Peak District area of Derbyshire and South Yorkshire. The Irish sub-species of Mountain Hare (the Irish Hare) was recorded on too few squares for a separate trend to be calculated. Table 3. Changes in abundance of Grey Squirrel, Red Fox and Red Deer between 1995 and 2005. Conventions as in Table 2.
Grey Squirrel Sciurus carolinensis. Overall in the UK, numbers increased significantly between 1995 and 2005. Numbers increased significantly in Wales and in England overall, and within the English regions of the East of England, South East and South West. The Grey Squirrel is a widespread species in England and Wales, but is more localised in Scotland (mainly central lowlands) and Northern Ireland. Red Fox Vulpes vulpes. There was a significant decline in numbers in the UK between 1995 and 2005. Apart of the South East of England where a significant increased was recorded, numbers declined in all of the countries and regions where this species was recorded on enough squares for trends to be calculated. The Red Fox is a widespread species across the UK Red Deer Cervus elaphus. No significant change in numbers was detected in the UK between 1995 and 2005. Following recommendations in Newson et al. 2006, to reduce the influence that a small number of sites recording large herds can have on the trends of this species, an alternative model distribution was fitted to these data. A small number of counts from deer parks were also excluded from the dataset. The Red Deer is a widespread species across much of the UK, although the majority of BBS records were located in Scotland where the bulk of the population resides. Table 4. Changes in abundance of Fallow Deer, Roe Deer and Reeves’s Muntjac between 1995 and 2005. Conventions as in Table 2.
Fallow Deer Dama dama. No significant change in numbers was detected in the UK between 1995 and 2005. Following recommendations in Newson et al. 2006, to reduce the influence that a small number of sites recording large herds can have on the trends of this species, an alternative model distribution was fitted to these data. A small number of counts from deer parks were also excluded from the dataset. The majority of BBS squares reporting Fallow Deer are in England, although this species is recorded sparingly across the UK. Roe Deer Capreolus capreolus. Roe Deer numbers increased significantly in the UK between 1995 and 2005, although there has been a gradual decline in numbers since a peak was reached in 2002. Numbers have also increased significantly in England over the survey period, and within the South East and South West regions, and the Easterly lowlands of England and Wales. The Roe Deer is a widespread species throughout much of Scotland and England, although it is curiously scarce in central England. This species is absent from Northern Ireland and rare in Wales. Reeves’s Muntjac Muntiacus reevesi. Numbers increased continuously in the UK between 1995 and 2002. This was then followed by a gradual decline, although there has been no significant change over the entire survey period (1995-2005). Muntjac Deer are primarily found in south and central England and Wales. However, north of the Humber, occurrence is patchy, but it does reach close to the Scottish border. Further reading Newson, S.E. & Noble, D.G. (2005) The production of population trends for UK mammals using BBS mammal data, 1995-2002. BTO Research Report No. 360. BTO, Thetford. Newson, S.E. & Noble, D.G. (2005) The production of population trends for UK mammals using BBS mammal data: 1995-2003 update. BTO Research Report No. 404. BTO, Thetford. Download report (.pdf 848Kb*) Newson, S.E. & Noble, D.G. (2006) The production of population trends for UK mammals using BBS mammal data: 1995-2004 update. BTO Research Report No. 428. BTO, Thetford. Download report (.pdf 1.71Mb*) * Needs Adobe Acrobat Reader - download a copy here
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The
TMP report shows that overall, 40% of native mammal species are
increasing, 12% are declining, 16% have stable populations and for
32% the trends are unclear at present, with more years of data required
before population change can be reliably assessed. For non-native
species, 66% are increasing, 11% are declining and 22% have stable
populations. The Partnership plans to introduce new surveillance
schemes over the next few years for as many of the remaining land
mammal species as possible. The BBS is an important component of
the TMP surveillance programme and we would like to thank all the
volunteers who have contributed mammal data and hope they will continue
to do so in the future.
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