Mammal monitoring

Muntjac by Paul Newton

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, 90% of BBS observers now actively look for them during their BBS visits.

Download the instructions for monitoring mammals on BBS

Mammal trends to 2016

BBS count data are used to calculate population trends for nine relatively widespread mammal species, shown below. These trends cover the period 1995–2016.

In 2016, 3,452 of the 3,837 BBS squares surveyed, mammals were actively recorded. In 2,883 squares, live mammals were seen and counted, 447 squares found no evidence of mammals and, on 122 squares, only indirect evidence was seen, such as field signs or via local knowledge.

Of the nine mammals for which trends can be produced from BBS counts, two have increased significantly in the UK as a whole since 1995: Roe Deer (64%) and Reeves' Muntjac (104%). Trends for herd mammals, for example, Red and Fallow Deer, should be interpreted with caution. This is because the presence or absence of a herd in a given BBS visit could heavily influence the overall trend for that species.

Two mammals have declined significantly: Grey Squirrel (9%), Rabbit (61%), Brown Hare (12%) and Red Fox (39%). The drivers behind these declines are unknown.

More information on the mammals recorded during the 2016 BBS surveys can be seen in the latest BBS Report (pages 28-29).

The information on species detected more often by signs of their presence than by sightings (e.g. Hedgehog, Mole and Badger) can also be used to estimate trends, although these require more careful interpretation.

Species
Trend 96-15
Significant
Sample
Grey Squirrel
-9
*
736
Rabbit
-61
*
1,418
Brown Hare
-12
*
706
Mountain/Irish Hare
-33
50
Red Fox
-39
*
284
Reeves' Muntjac
104
*
95
Red Deer
14
64
Fallow Deer
13
62
Roe Deer
64
*
418

• This table shows unsmoothed trends (in bold) and sample sizes (normal font). 
• Population changes are shown for mammal species for which the sample size is at least 30 squares.
• Trends are percentage changes, and are marked with an asterisk (*) where significant at the 95% level or more.
• The sample is the mean number of squares on which the species was recorded  

Brown Hare - East Midlands

Brown Hare BBS trend in East Midlands (1995–2016)
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Brown Hare - East England

Brown Hare BBS trend in East of England (1995–2016)
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Brown Hare - England

Brown Hare BBS trend in England (1995–2016)
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Brown Hare - North West England

Brown Hare BBS trend in North West England (1995–2016)
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Brown Hare - Scotland

Brown Hare BBS trend in Scotland (1995–2016)
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Brown Hare - South East England

Brown Hare BBS trend in South East England (1995–2016)
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Brown Hare - South West England

Brown Hare BBS trend in South West England (1995–2016)
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Brown Hare - UK

Brown Hare BBS trend in the UK (1995–2016)
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Brown Hare - West Midlands

Brown Hare BBS trend in West Midlands (1995–2016)
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Brown Hare- Yorkshire and Humber

Brown Hare BBS trend in Yorkshire (1995–2016)
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Fallow Deer - England

Fallow Deer BBS trend in England (1995–2016)
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Fallow Deer - UK

Fallow Deer BBS trend in the UK (1995–2016)
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Grey Squirrel - East Midlands

Grey Squirrel BBS trend in East Midlands (1995–2016)
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Grey Squirrel - East England

Grey Squirrel BBS trend in East of England (1995–2016)
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Grey Squirrel - England

Grey Squirrel BBS trend in England (1995–2016)
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Grey Squirrel - London

Grey Squirrel BBS trend in London (1995–2016)
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Grey Squirrel - North West England

Grey Squirrel BBS trend in North West England (1995–2016)
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Grey Squirrel - South East England

Grey Squirrel BBS trend in South East England (1995–2016)
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Grey Squirrel - South West England

Grey Squirrel BBS trend in South West England (1995–2016)
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Grey Squirrel - UK

Grey Squirrel BBS trend in the UK (1995–2016)
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Grey Squirrel - Wales

Grey Squirrel BBS trend in Wales (1995–2016)
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Grey Squirrel - West Midlands

Grey Squirrel BBS trend in West Midlands (1995–2016)
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Grey Squirrel- Yorkshire and Humber

Grey Squirrel BBS trend in Yorkshire (1995–2016)

Mountain / Irish Hare - UK

Mountain/Irish Hare BBS trend in the UK (1995–2016)
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Rabbit - East Midlands

Rabbit BBS trend in East Midlands (1995–2016)
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Rabbit - East England

Rabbit BBS trend in East of England (1995–2016)
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Rabbit - England

Rabbit BBS trend in England (1995–2016)
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Rabbit - North East England

Rabbit BBS trend in North East England (1995–2016)
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Rabbit - North West England

Rabbit BBS trend in North West England (1995–2016)
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Rabbit - Northern Ireland

Rabbit BBS trend in Northern Ireland (1995–2016)
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Rabbit - Scotland

Rabbit BBS trend in Scotland (1995–2016)
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Rabbit - South East England

Rabbit BBS trend in South East England (1995–2016)
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Rabbit - South West England

Rabbit BBS trend in South West England (1995–2016)
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Rabbit - UK

Rabbit BBS trend in the UK (1995–2016)
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Rabbit - Wales

Rabbit BBS trend in Wales (1995–2016)
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Rabbit - West Midlands

Rabbit BBS trend in West Midlands (1995–2016)
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Rabbit- Yorkshire and Humber

Rabbit BBS trend in Yorkshire (1995–2016)
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Red Deer - Scotland

Red Deer BBS trend in Scotland (1995–2016)
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Red Deer - UK

Red Deer BBS trend in the UK (1995–2016)
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Red Fox - East England

Red Fox BBS trend in East of England (1995–2016)
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Red Fox - England

Red Fox BBS trend in England (1995–2016)
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Red Fox - South East England

Red Fox BBS trend in South East England (1995–2016)
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Red Fox - South West England

Red Fox BBS trend in South West England (1995–2016)
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Red Fox - UK

Red Fox BBS trend in the UK (1995–2016)
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Roe Deer - England

Roe Deer BBS trend in England (1995–2016)
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Roe Deer - Scotland

Roe Deer BBS trend in Scotland (1995–2016)
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Roe Deer - South East England

Roe Deer BBS trend in South East England (1995–2016)
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Roe Deer - South West England

Roe Deer BBS trend in South West England (1995–2016)
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Roe Deer - UK

Roe Deer BBS trend in the UK (1995–2016)
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Comparison of BBS mammal trends with the National Gamebag Census

In 2011 the JNCC funded work to compare BBS mammal trends between 1995 and 2009 with another annual scheme: the National Gamebag Census (NGC), carried out by the Game and Wildlife Conservation Trust. The NGC is a voluntary scheme that collects bag statistics from shooting estates, on average about 650 per year. The aim of the project was to produce an overview of trends in abundance and distribution. 

Of nine species tested, none differed significantly in their trends between the two schemes. For four species where BBS indicated significant increases between 1995 and 2009, the NCG trend was either not significant (Red Deer, Roe Deer and Reeves’ Muntjac) or alsoshowed a significant increase (Grey Squirrel). Rabbit showed a significant decline on BBS whereas NGC found no significant change.

This work demonstrated the feasibility of producing joint BBS-NGC trends for assessing population change for statutory purposes where a single figure is needed. Results of the spatial mapping were also useful, inshowing areas where species are most often detected and where the most marked changes had occurred. However, due to differences in sampling design and methods, the recommendation is to routinely report temporal and spatial results from the two schemes separately.