Predator and mountain hare culling on grouse moors

Comes from

A Wild Justice Petition, which can be found here:

Ban driven grouse shooting; wilful blindness is no longer an option.

Chris Packham, Ruth Tingay and Mark Avery (Wild Justice) believe that intensive grouse shooting is bad for people, the environment and wildlife. People; grouse shooting is economically insignificant when contrasted with other real and potential uses of the UK’s uplands. Environment; muirburn impacts negatively upon climate change and drainage leads to flooding and erosion. Wildlife; the wholesale culling of all predators and Mountain Hares has a disastrous effect on the ecology of these areas and the industry is underpinned by a criminal tradition of raptor persecution which shows no signs of abating. It’s time to provide an opportunity to implement immediate, legislative and meaningful measures to address this abhorrently destructive practice.

What the Science Says – the fuller picture

There are two main points to examine in the overall wildlife claim: 

the wholesale culling of all predators and Mountain Hares has a disastrous effect on the ecology of these areas…

1. Does the wholesale culling of all predators and mountain hares take place?
2. Does this have a disastrous effect on the ecology of these areas?

This piece will explore what is known about predator culling, why it is carried out, and establish whether wholesale culling of all predators is accurate. Then we will look at the impact this has on other species, to understand if the evidence supports the claim that it has a disastrous effect on the local ecology.

Does the wholesale culling of all predators and mountain hares take place?

Predator control is carried out on grouse moors. It is the lethal control of certain abundant generalist predator species using specific techniques, which is allowed under UK law. The methods used are regulated by the legislation and are also guided by best practice codes. However, the claim “wholesale culling of all predators” can be interpreted in two ways – extensive culling on a large scale either of all predator species, or all individuals of a species. This article will consider both.

Why do grouse moors control predators?

The modern world has created an environment where generalist predators thrive to the extent that they can seriously reduce the breeding success and numbers both of gamebirds managed for sport shooting and other ground-nesting species, notably waders. Legal control of these common predators as part of game management has been shown to be effective for improving the survival of gamebirds and some other bird species during the breeding season. One study found that control of foxes and crows led to a threefold increase in breeding success of red grouse and an increase in breeding numbers, which declined when there was no predator control². Furthermore, controlling multiple predators within a moor, instead of just one species, has been shown to be more effective².

Legal predator control on grouse moors, as part of game management, is designed to protect gamebirds, but also has benefits for some other prey species. The species which are predominantly controlled are common and abundant, and legal predator control does not threaten their conservation status.

How many and which predators are culled?

Legal predator control 

Many predator species that are found on grouse moors are protected, for example bird of prey species, while common and abundant predators can be culled only using certain methods that are subject to use under government-recognised Codes of Practice. Common predators that are legally controlled include foxes, carrion crows, hooded crows, stoats, weasels, rats and feral cats³. There is strong evidence that illegal killing of birds of prey also occurs on grouse moors (see below).

To explore the extent of legal predator culling on grouse moors and understand whether all individuals are killed, a paper from 2010 can offer some answers. In this study, the authors performed an eight-year field experiment on moorland near Otterburn in Northumberland, where they maintained consistent habitat conditions but controlled predators, including foxes, carrion crows, stoats and weasels, according to best practice. During the study period, there was a 43% reduction in foxes and 78% reduction in crows recorded on the area. There were no detectable changes in the low numbers of stoat or weasel². They found that the number of predators culled did not consistently decrease during the years of the study, even though predator control continued. This was thought to be because of predator immigration from neighbouring areas that were unkeepered replacing those individuals that were culled. 

Predator control did significantly reduce numbers of foxes and crows, but did not remove all of them from the area². 

Illegal killing of birds of prey

The illegal killing of several species of birds of prey (raptors), including for example golden eagle, peregrine and particularly hen harrier, has repeatedly been shown to occur on grouse moors, especially those managed for driven shooting and this is thought to be the main factor preventing hen harrier numbers recovering in England^4-7. A recent paper following satellite-tracked hen harriers found that birds were ten times more likely to die or disappear over a grouse moor than an area not managed for grouse⁸. This is explored further in a separate fact check.

Despite evidence that illegal killing does occur, and at a large enough scale to significantly impact numbers of some birds of prey, the extent to which they are illegally killed and the number remaining (to determine the accuracy of the claim that all predators are killed) is not known. 

Peregrine falcon populations have lower breeding success on grouse moors compared to non-grouse moors⁹. Introduced red kite populations in Scotland have been found to grow more slowly in areas with grouse moors, and Scottish golden eagle populations are also affected – both because of illegal killing by poisoning^10-12. The lower numbers of birds of prey may have a wider impact on moorland ecology, but published evidence on this is very limited.

One paper from 2001 on breeding moorland birds recorded the number of sightings of buzzard, hen harrier, kestrel, merlin, peregrine falcon and raven on grouse moor and non-grouse moors. All these species were present, with significantly more buzzards and significantly fewer hen harriers seen on grouse moors than other moors, and other species equal (on further analysis, when regional effects were considered, merlin numbers were also lower on grouse moors)¹³. This supports the evidence that some species of birds of prey are illegally killed and their numbers are lower, but that in this study they remain present. The number of other species on moors in this study does not appear to be affected, which suggests that if illegal killing occurs for these species it is at a lower level, but does not provide proof that they are never targeted. Another unpublished report on where breeding merlin are found suggested that 80% of areas that contain merlin were on grouse moors, with 20% on non-grouse moors¹⁴. 

In the absence of illegal killing, it has long been thought that grouse moors can provide good habitat for raptors¹⁵. Hen harrier breeding numbers tend to be high where meadow pipits and voles are most abundant, for example on moors with a mixture of grassy and heather areas like those in the Joint Raptor Study at Langholm Moor^16-19. In the previously mentioned 2010 study at Otterburn, significantly more raptor sightings were made on plots with active predator control, compared to those without². 

Studies identify that grouse moors have the potential to benefit raptor conservation by supporting large amounts of prey^20,21 along with low levels of predation on the harriers’ own nests¹⁷. One study showed that hen harrier breeding success was higher when a moor was keepered, likely as a result of reduced predation on hen harrier eggs and chicks, particularly by foxes, which was found to be the main cause of breeding failure¹⁷. Hen harrier numbers at Langholm fell from 20 in 1997 to between two and five pairs over the next five years after gamekeeping ceased. Hen harrier breeding success, which had averaged 2.5 chicks fledged per female per year with 80% of breeding attempts successful, fell to 1.2 chicks per female and 39% of breeding attempts successful when the moor became unkeepered (2000-2007) and foxes and crows were not controlled²². However, in these studies the scientists were able to control every aspect of moorland management and therefore no illegal killing of raptors took place.

These examples demonstrate that without illegal killing, elements of moorland management can benefit raptors, but where illegal killing continues this potential is unfulfilled and the effect on the raptor species remains negative, with possible effects on the wider ecology. Evidence is lacking to suggest what proportion of landowners do or do not accept or expect illegal killing on their moor. 

Mountain hares

Mountain hares are protected; they are listed under Annex V if the EU Habitats Directive (1992) as a species “of community interest whose taking in the wild and exploitation may be subject to management measures”. Furthermore, Article 14 of the directives does require member states to ensure that the exploitation of such a species “is compatible with their being maintained at a favourable conservation status”²³. In Scotland, as of 1 March 2021, they became a fully protected species and are now included on Schedule 5 of the Wildlife and Countryside Act 1981. This change means that no one can intentionally or carelessly kill, injure, take, sell or transport for the purpose of sale mountain hares without a licence from NatureScot¹. Prior to March 2021, hare numbers were reduced by culling on many Scottish grouse moors because hares are vectors of ticks, which carry the louping ill virus causing serious disease in grouse. However, NatureScot has stated it will not issue a licence for tick-related culls to support red grouse numbers until further research has been conducted into the effectiveness of these culls.

Almost the entire UK population of mountain hares is found in Scotland, and a paper published in 2020 gives information on Scottish mountain hare distribution and the number culled²⁴. Another paper examining the number of mountain hares culled between 2016 and 2017 found that 33,582 were killed on 88 estates. Of these, 70 were driven grouse moors, 11 were walked-up grouse moors and 7 did not shoot grouse²⁵. The authors found no relationship between the kill density and changes in mountain hare range at the estate level. In fact, areas with driven grouse shooting had greater numbers of mountain hares compared to walked-up grouse shooting or no-shooting areas²⁵. Two-thirds of the range in which mountain hares were found occurred on estates with driven grouse shooting²⁵. 

These two papers suggest that although mountain hare culls were carried out on Scottish grouse moors in 2016 and 2017 (before mountain hare culling was licensed), not all mountain hares were killed. In general, there is a lack of evidence about mountain hare numbers and to address this Scottish National Heritage (now NatureScot) published a report in 2020 to establish a national monitoring scheme for mountain hare in Scotland26. Previously, there has been no standardised counting method or coordinated national scheme, although hare numbers were regularly recorded when red grouse were counted as part of a long-term grouse monitoring scheme⁶. This has led to difficulty when comparing results across different locations and time. Establishing this monitoring scheme is an important step that will allow a better estimation of the numbers of hares on grouse moors and elsewhere in Scotland. Together, this evidence supports the conclusion that mountain hares and predators are culled on grouse moors – both legally and illegally – but there is not enough evidence to support the claimed wholesale killing of all predators and mountain hares.

What is the effect of controlling predators on the local ecology?

Moorland birds

A reduction in abundant generalist predators is beneficial to most ground-nesting upland birds, some of which are of conservation concern. Legal predator control has been reported to benefit curlew, merlin, red grouse, black grouse, golden plover, lapwing, snipe, greenshank, buzzard, short-eared owl and black-headed gull^13,27,28 as well as mountain hares^24,25. There is evidence that other species including carrion crow, whinchat and skylark do less well on grouse moors¹³, in some cases because they prefer a grassier environment. The effect of legal predator control can differ from the overall impact of grouse moor management. 

An experimental study examining the effect of predator control alone has demonstrated the importance of legal predator control for some moorland bird species. Introducing predator control led to an average threefold increase in the breeding success of lapwing, golden plover, curlew, red grouse and meadow pipit², translating into an increase of 14% per year in the breeding numbers of lapwing, curlew, golden plover and red grouse². Without predator control, the populations declined by 17% per year². This ten-year GWCT Upland Predation Experiment indicated that curlew numbers would fall by 47% in a decade if gamekeepers stopped controlling generalist predators, even if the habitat was maintained. The low breeding success seen on moors where predators were not controlled in this experiment could also lead to a drop in lapwing and golden plover numbers of 81%, after ten years²⁹.

Looking at the wider literature on the impact of predator control, there is evidence that gamebirds, seabirds, and wader populations can all be limited by predation. Single-brooded species are more likely to be limited by predators, compared to multi-brooded species³⁰. If predator control of foxes and corvids is carried out simultaneously, it is more likely to be effective^30,31. A review of five wader species in Western Europe (oystercatcher, lapwing, black-tailed godwit, curlew and redshank) found that nest predation has increased by around 40% in the last four decades. Although adult survival remains high for these species, chick survival and nest success have both declined, and breeding numbers are falling³². An eight-year experiment into the effect of red fox and carrion crow control on lapwing in the UK lowlands found predator control was most likely to cause an increase in nest survival on sites where there were higher numbers of those predators in the first place³³. A review published in 2018 found predator control, as part of game management, did have a positive effect on other wildlife, beyond game, but there was a negative element caused by illegal predator control³⁴. There were stronger positive effects on breeding success, rather than population density, suggesting predator control is aiding nest success, which is a result consistent with other studies³⁴. 

In a study of red grouse management as a whole on breeding birds, breeding golden plover and lapwing densities were found to be five times higher than on grouse moors compared to other moors, while curlew were twice as high. However, meadow pipit, skylark, whinchat and carrion/hooded crow were less abundant on grouse moors13. Within this, the authors broke down the elements of grouse moor management, including predator control. They found there was a possible positive influence of predator control of crows on red grouse, golden plover and lapwing. The negative effect on meadow pipit was caused by heather burning13. Legal predator control can therefore benefit several wader species where moorland is becoming their stronghold as populations continue to decline in lowland areas, but the illegal killing of birds of prey has a serious negative impact on those species.

Mountain hares

Relatively little is known about mountain hare numbers, and the impact of culling on grouse moors is not well understood. It is challenging to count hares and make estimations as their detectability varies with the habitat and vegetation²⁴. The lack of a national monitoring scheme and no mandatory requirement to report hunting bags, along with the contradictory evidence for changes in numbers have all caused differing opinions on mountain hare status²⁴.

Studying the distribution of mountain hares across Scotland has shown no change in the overall area they occupy, but changes in range have been observed between regions and sites of differing grouse management intensities25. A GWCT study on spatial and temporal variation in mountain hares found densities are either stable or increasing on driven grouse moors when compared to moorland not managed for driven grouse shooting, where they are in decline by about 40% per year in some areas²⁴. Overall, the range of mountain hares was found to have expanded in areas practising driven grouse shooting and declined in areas with walked-up shooting and in the south-west of Scotland, where grouse shooting has largely ceased²⁵. Even though there has been an increase in the number of hares killed over the last 20 years, the decrease in range seen may be unrelated to culling. Instead, it could be caused by other changes such as moorland habitat loss and change in management²⁵.

Mountain hare populations fluctuate naturally for many reasons: parasites, weather, predation, and habitat quality. The natural fluctuations in their numbers are more pronounced where there are higher densities, as seen on driven grouse moors²⁴. Therefore, when examining long-term population trends, caution is needed when only using one or two cycles to draw conclusions²⁴. More information on mountain hare numbers on grouse moors can be found here.

In summary

Although both legal and illegal predator control takes place on grouse moors, the scientific evidence does not support the statement that all predators and mountain hares are culled. These activities have mixed effects on the local ecology, with negative impacts particularly for those species that are legally controlled or illegally killed, but also well-recognised and documented positive effects for other species, particularly some moorland breeding birds. However, until the illegal killing of birds of prey stops it will continue to overshadow the other aspects of grouse moor management.

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References

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