Is the badger population out of control?

April 2013

“Since the badger was made a protected species in 1973 the population has been expanding out of control…”

“The badger, a species without natural predators, is a classic example of a population out of control.”

The Veterinary Association for Wildlife Management

So is the badger population really growing out of control and if so, is this because of increased legal protection and the absence of any natural predators?

In order to answer these questions, we must first:

1. Establish what the current badger population size is and how this has been changing over time; and

2. Understand what causes badger populations to increase or decrease.

The difficulties of counting badgers

Badgers are shy, nocturnal, group-living social animals that live in setts, an underground system of tunnels and chambers shared by members of the same social group. Each badger group generally has one main sett and several additional setts that are used to varying extent by members of the group. Most setts generally have several entrances. These ecological and behavioural characteristics of badgers make them notoriously difficult to count accurately or to estimate average group size. Furthermore, badger social group sizes are known to vary greatly according to habitat and other factors (Fera 2012). So even if every main sett in a given area is identified reliably, which in itself requires some experience, it remains extremely difficult to establish how many badgers there are in the wider population without further study.

In the Southwest of England, for example, average group size is between 5-6 adults, but this is in an area known to have a particularly high badger population density. In other areas, groups of 2-3 adults are more usual.

So what do we know about the current size of the UK badger population?

It is generally agreed that badger populations have recovered during the course of the 20th century due to increased legal protection from persecution and hunting. But nobody actually knows how many badgers there are in the UK – or indeed, how many there were prior to increased legal protection.

There have been only two national assessments of the number of badger social groups in Great Britain up to now, one in the mid-1980s and one in the mid-1990s. These suggested an increase in both the number of badger social groups (by c. 24%) and in the average size of a badger social group (by c. 47%). As a result, these surveys suggested a large increase in population size between the two surveys, which was partly attributed to lower levels of persecution following the introduction of new laws. Since then, however, the accuracy of these earlier population estimates has been questioned especially because of the difficulties of accurately determining the number of badgers in each social group (Fera 2012).

In 2011, Natural England estimated there to be around 220,000 badgers in England based on a 2005 assessment of available data by the Joint Nature Conservation Committee (JNCC) under the Tracking Mammals Partnership, which estimated there to be 190,000 badgers in England. The JNCC  estimated the total UK badger population to be 288,000 (Battersby 2005). These are the best estimates available of the English and UK badger populations at present. However, a new badger sett survey for England and Wales was commissioned by Defra in November 2011 and is being undertaken by Fera. Results are expected some time after June 2013. The survey is viewed as a continuation of the two earlier nationwide surveys and aims to contribute to the long-term monitoring of trends in numbers and distribution of badgers over time including regional variations. The current survey will monitor the same areas surveyed in the earlier surveys.

It should be noted that badger populations and densities (i.e. the average number of badgers in a given area) vary geographically. For example, the 1980s and 1990s surveys suggest that 45% of England’s badger population is found in the West Midlands and Southwest regions of England; badger densities are also especially high in parts of the west of England (Natural England 2011, p.4, Paragraph 21).

Also in 2011, Fera was commissioned by Defra to undertake a desk-based study of recent research on badgers across England and Wales to assess the suitability of existing data for estimating badger population abundance. The study concluded that it was not possible to use the data from more recent small-scale surveys and studies to compare with the two earlier national badger surveys. Nor could these be used to say anything significant about the wider or national badger population size and distribution. In order to be able to do that, the earlier national surveys would need to be repeated using similar methods to allow comparison of data between the different surveys (Fera 2011, p.17). The Fera study also noted that:

“…in order to translate estimates of numbers of social groups in England and Wales into estimates of numbers of badgers, it may be necessary to collect additional data on social group sizes representing different regions and landscapes.”  (Fera 2011, p. 16)

In 2012, Fera was again commissioned by Defra to assess badger social group size in different landscapes across England and Wales with a view to coming up with mean badger group sizes that can be used in conjunction with the results of latest badger sett survey to estimate the size of the badger population in England and Wales. This study is due run until 2013. We have not established its current status or if any findings are available yet.

So what have been the impacts of legal protection on the badger population?

Even Defra seems to prefer to err on the side of caution when it comes to commenting on the national badger population size and the effects of increased protection on the badger population size. For example, Question 9 in  Annex G on Frequently Asked Questions, which was among the documents circulated by Defra for its 2010 consultation on Bovine Tuberculosis asks:

Q. 9  “Are there more badgers in England and Wales since the Protection of Badgers Act 1992 came into force?”

In reply, Defra’s states:

“Two national assessments have been made of the number of badger social groups in Great Britain over this time, one in the mid-1980s and another in the mid-1990s. These two surveys indicated an increase from around 42,000 social groups to around 50,000 social groups over this 10-year period. There is considerable uncertainty around actual population estimates because it is hard to determine how many badgers there are in each social group.

The Protection of Badgers Act came into force between these two surveys and it is not possible to determine to what extent change happened before or after the Act came into force. No national survey of badgers in England or Wales has taken place since the 1990s and so it is not possible to estimate populations now or determine how populations might have changed since the mid 1990s although there is local evidence of increased numbers.”

Defra 2010, Annex G, pp.2-3).

Defra has reiterated its view on the limitations of past badger surveys more recently:

“A drawback of previous national surveys has been the limited available data on typical group sizes, causing difficulties in translating the estimated abundance of social groups into meaningful estimates of badger abundance. This is particularly problematic as it is known from long-term intensive studies that badger population size can vary due to changes in numbers of social groups, or changes in group sizes, or both (e.g. Rogers et al 1997). Additionally, badger social group size may vary over time and space. Relatively small bias in estimates of group size could lead to significant error if applied to estimates of social group abundance at national or regional scales.”

Source: http://randd.defra.gov.uk/Default.aspx?Menu=Menu&Module=More&Location=None&Completed=2&ProjectID=18396, accessed 7 April 2013

Badger population regulation

Contrary to popular perception, long-term studies of badger population dynamics have shown that badger populations do not just keep growing endlessly even in the absence of predators. This should not really come as a surprise since in order to grow and reproduce, badgers require food, and the supply of food is limited.

Woodchester Park in Gloucestershire and Whytham Woods in Oxfordshire are two areas where badgers have been studied since the 1970s. These long-term research projects have provided invaluable information about many aspects of badger ecology, social behaviour and, in the case of Woodchester Park, also about bovine TB in badgers. The badger population at Woodchester Park more than doubled between 1978 and 1990, remained constant between 1990-97, reached a peak in 1999 before starting to decline steadily until 2004. At Whytham Woods, the badger population also more than doubled between 1987-96, decreased in the late 1990s and then showed a slight increasing trend between 2000-02 (see references in Fera 2012 for both sites, pp. 4-5).

Badgergate was not able to establish what happened to the badger population after 2002 and 2004, in Whytham and Woodchester Park, respectively, but it is clear from these data that even in the absence of predators, the badger population does not just keep rising steadily, but rather fluctuates due to other natural factors. Although both these research areas are relatively small and have a relatively high density of badgers, there is no reason to think that badger populations in other areas would not also fluctuate naturally.

Like most other species, badger populations are limited by a number of factors including availability of suitable habitat and adequate food supply. The British badger is especially fond of earthworms – and even more so than some of its Mediterranean compatriots it seems. The availability of earthworms is in turn determined by a range of other factors. For example, research by the Wildlife Conservation Research Unit (WildCRU), Oxford University suggests that climate change may affect badger survival and successful reproduction as climate affects food availability, foraging patterns and cub survival (MacDonald et al. 2010)

In common with other long lived species, badger numbers are actually regulated through decreased reproduction, as badger density increases in response to the availability of food. As populations increase towards the maximum ecological carrying capacity (the maximum number of a species that a given area of habitat can sustain), the number of cubs produced decreases.

Conclusion

Q: So will the badger population just continue to grow and grow and grow given that the badger has no natural predators?

A: EXTREMELY unlikely.

We hope this short note helps to put to rest this particular myth about the badger population being ‘out of control’ in England and Wales. Tigers, lions, rhinos, giant anteaters and giraffes are all examples of other species whose numbers are not regulated by natural predation.

Additionally, we hope that we have managed to convey some of the challenges involved in estimating badger populations accurately in Britain and the current state of knowledge about the size of the badger population in England and Wales.

References:

Battersby, J. (Ed.) & Tracking Mammals Partnership 2005. UK Mammals: Species Status and Population Trends. First Report by the Tracking Mammals Partnership. JNCC/Tracking Mammals Partnership, Peterborough. http://jncc.defra.gov.uk/pdf/pub05_ukmammals_speciesstatusText_final.pdf.  Accessed May 2013.

Defra 2010. Frequently Asked Questions. Annex G to consultation document for the 2010 Defra consultation on the Government’s approach to Bovine TB management and badger control. Accessed September 2012 at http://archive.defra.gov.uk/corporate/consult/tb-control-measures/index.htm. However, this link no longer works as of April 2013 at least and Badgergate was not able to locate the documents through the national archives. However, the consultation document and associated annexes can still be traced online via other websites along with the final summary of consultation responses, which were published in 2011.

Fera 2012. Desk based assessment of badger population data. Evidence Project Final Report. 20120514 evid4 SE3128 revised May 12 uploaded 5July2012 Accessed April 2013. Although this study was completed in late 2011, its final report (based on the URL Link title) seems to have been uploaded online only in July 2012. 

Macdonald, D.W, Newman, c. Buesching, C.D & P. Nouvellet. 2010. Are badgers ‘Under the Weather’? Direct and indirect impacts of climate variation on European badger (Meles meles) population dynamics. Global Change Biology (2010) 16: 2913–2922. doi: 10.1111/j.1365-2486.2010.02208.x

Natural England 2011.The impact of culling on badger (Meles meles) populations in England and measures to prevent their ‘local disappearance’ from culled areas. Supplementary advice provided under the Protection of Badgers Act 1992 and Wildlife & Countryside Act 1981 (as amended). 4 July 2011. http://www.marycreagh.co.uk/fileadmin/mary_creagh/user/Natural_England_-_Advice_to_Defra_-_Control_of_Badgers_-_Jul_11_-_Redacted.pdf. Accessed April 2013.

Wilson, G., Harris, S & McLaren, G. 1997. Changes in the British badger population 1988-97. People’s Trust for Endangered Species (PTES), London.  http://www.ptes.org/files/2067_changes_in_the_british_badger_population_1988_to1997_fullsearcable.pdf   Accessed May 2013. 

Notes:

Badgers are protected under the Badger Act, 1973 Schedule 5 of the Wildlife and Countryside Act, 1981 and the Protection of Badgers Act, 1992.