William Powell Country

Is There Only One Grouse Disease?


Article written by 12 July 2012

The answer is clearly no, but for anyone involved in grouse moor management over the past 100 years or so, it has been largely accepted that the only “diseases” that grouse suffer from are the Strongyle Worm and to a very limited extent outside of some parts ofScotland, Louping ill.  Clearly a worm is not a disease, but for all intents and purposes, we have had very little experience of any diseases which kill large quantities of grouse.  Compare that to pheasants and partridges which are prone to several diseases which kill, often in large numbers.  These include; Hexamita, Coccidiosis, Gapes, Blackhead and Fowl Pest to name but a few.  Indeed it would be fair to say that almost every low ground shoot experiences disease to some extent in their birds.  As a result low ground keepers have built up a very sophisticated arsenal of medicines to try and control these diseases.  However,  partridge and pheasant keepers also know how difficult it is to introduce medicine into their birds, once they are out of the release pen and living in the wild.

Contrast that with grouse keepers.  They have historically had to get used to the ups and downs of what was known as the grouse cycle – often thought to last seven years.  The downs of the cycles have almost always been caused by a build-up of Strongyle worm.  Apart from that, disease amongst grouse is pretty well unheard of and because the Strongyle worm is the main grouse killer (after man!), we have taken the view that if we can get on top of the worm everything else will fall into place.

In the last two years on  perhaps as many as twenty-five moors, grouse often in reasonable quantities (over 100 on one moor alone), have been found dead or barely alive, apparently due to a phenomena known as “Bulgy Eye”.  Almost certainly, this is a form of Mycoplasma which is a relatively common disease in all sorts of poultry and game birds.  It is literally evidenced by severely protruding eyes.  Either grouse keepers have been remarkably unobservant or until a couple of years ago, Bulgy eye has not been present on grouse moors.  The fact that it is now occurring on moors many miles apart and in both the north ofEnglandandScotland, seems to suggest that the disease itself is pretty widespread. Why has this only recently occurred?

Because many grouse moor owners have in recent years invested large amounts of money in their moorland Estates, resulting in better management and keepering, we have arrived at a situation where there has been on many of the well run moors, very large populations of grouse year in and year out.  These populations are far far larger than what we were used to even a decade ago.  There is the belief, most usually among many of the newer owners but also amongst their keepers, that we have advanced to a stage where grouse crashes are a thing of the past.  The reason why they believe this to be true is that modern wormers (usually contained in medicated grit), are much more efficient than they used to be.  The use of medicated grit means that the strongyle worm population in grouse can now be kept very low.  Medicated grit has been in use for over 25 years, but originally the wormer used was at a lower strength and routine gritting did not occur on the scale it now does.  Because of the questionable efficiency of the original medicated grit used, direct dosing of caught grouse was developed.  This flushed out all the worms and is extremely effective particularly when followed up by using medicated grit.  That at least is the theory and many people believe that the consistency of high to very high grouse bags in recent years proves this works.

It is always easy to be a doubter.  However, I am not convinced that what we are experiencing is quite as simple as many people think.  Firstly, because if you look at the bags on some grouse moors many years before any form of intensive gritting, let alone medicated gritting came into being, you can find instances where large annual bags of grouse were sustained over many years.  This was true on Midhope Moor in South Yorkshire in the 1870’s and again true at Leadhills in south-westScotlandin the 1970’s.  Leadhills is a high wet moor (it always seems to be raining when I am driving on the A74 past Abbington Services!) and therefore Leadhills is an ideal “wormy” moor.   Yet throughout the 1970’s, it consistently shot high annual bags of grouse, with no meaningful crash occurring.

There are many other instances, including the very famous Broomhead Moor, which had many years of shooting very good seasonal bags in the period between the two World Wars, decades before medicated grit or direct dosing were thought of.  The success of Broomhead Moor was put down to the then Mr. Rimington-Wilson’s obsession with rigorous burning, equally rigorous vermin control and proper shooting pressure, which left the right grouse stock at the end of each season, being not too many and not too few.

We still know relatively little about why the Strongyle worm is sometimes present on a moor in high numbers and sometimes isn’t.  However, even though grouse numbers at Midhope, Leadhills and Broomhead Moors held up at certain times over long periods, they did eventually crash and the Strongyle worm was almost certainly to blame.

At the risk of being contrary (which I suspect I excel at), I wonder whether far from our wanting to routinely kill off the Strongyle worm, we haven’t had very good reason to be glad of its presence, albeit, we might not feel quite so well disposed towards it in years when we have had to cancel the entire shooting programme because of a major crash in grouse numbers!

What however, the Strongyle worm usually did was to build up as the numbers of grouse on the moor increased.  At a certain level when grouse numbers were high (and probably had been for a couple of seasons), the very high worm burden took it’s toll and large numbers of adult grouse died; first the territorial cocks in February found near water and then the hens in March and April, often sitting on nests.  This then left a small population of grouse on the moor and generally a very low worm burden as well. With good keepering and good luck, grouse numbers built up again and usually there was a shootable surplus within a couple of years.

I wonder whether as with the worm, without grouse in any numbers and the few that survived the crash being spread out over a large area of moorland, there was not the right conditions for other potentially fatal avian diseases to build up?  In other words, is the reason that we haven’t knowingly experienced deaths of large numbers of grouse before from Coccidiosis, a version of Gapes, Cryptosporidium, Bulgy Eye or any other disease which might affect the red grouse in one form or another, be because the grouse population has widely fluctuated and reasonably regularly been almost eliminated by the Strongyle worm, hence providing no hosts for any disease to get a proper foothold in?  You may say but surely that cannot be the case if moors such as Midhope in the nineteenth century and Broomhead and Leadhills in the twentieth century kept shooting good bags over longish periods of time without there being a crash?

What I think has changed is the level of stock over the last six or seven years being routinely left on many moors at the end of each season.  Many of the newer moorland owners have a not unreasonable desire to not only want to shoot more grouse but also as with reared pheasants and partridges, to consistently have grouse to shoot each year.  Again perfectly understandably, they do not want the unpredictability that grouse have traditionally been for most of us;  good some years, awful others.  They have wanted a more consistent “business” model and been prepared to invest to achieve this, including generously funding research which has led to the much improved medicated grit we now use today.  It is however,  just possible that improved grit may at least in part, be causing the current problem.

To achieve ever increasing bags with a wild bird all else being equal, you need to leave a correspondingly larger stock at the end of the previous season.  If this bigger stock breeds well, you will have more young grouse than were on the moor the previous summer.  I think the problem we now have is that the number of grouse being left at the end of the season are far in excess of what our forefathers routinely left.  I accept the amazing record bags which occurred at Abbeystead, Broomhead and Roanfell could only occur if exceptional stocks of grouse had been left the previous year.  However, in almost all cases, these were as a result of a natural build-up of numbers and there appears from the evidence that we have, to have been relatively little desire on the part of the then owners or their keepers to leave the sort of levels of grouse which are now being left on many of the moors in the North of England at the end of each and every year.  In years gone by, keepers’ shoots at the end of the season on well stocked moors were held, both to reward people who had helped out on shoot days, but also to further cull grouse numbers so as to leave the right level of stock to go into the winter with.  On some moors including Allenheads, keepers in the late season, would even shoot old cocks when sitting on the wall tops.

It is extremely difficult to accurately assess the level of stock that you need to leave to maximise output, assuming that a good breeding season follows.  However, in the “old” days it was definitely only occasionally that massive stocks of grouse were left, perhaps no more often than once every 10 or more years.  Now we have owners with a desire to optimise grouse numbers year on year.  Indeed the “optimum” figure seems to get larger as though there is no limit to the number of grouse the moor can hold.  There is nothing inherently wrong with this and clearly it has been happening up and down the country on low ground shoots for very many years.  The problem we have with grouse is that by being wild, they are incredibly difficult to treat should any manifestations of disease occur.  We may all have been guilty (including myself), of assuming that we can because of the effectiveness of modern wormers, maintain very large numbers of grouse over an extended period without there being any ramifications.  However, recent findings of still admittedly only occasional but increasing numbers of grouse with Bulgy Eye, might be indicating that we need a radical rethink of some of our current management and indeed stocking practices.  There is to date absolutely no evidence that the appearance of Bulgy eye in grouse has had anything to do with pheasants or partridges released onto the edge of the moor.  Indeed the majority of moors where Bulgy eye has so far been found, have no pheasants or partridges released nearby.

By leaving very large stocks of grouse at the end of every season, we may indeed be providing just the right conditions for Bulgy Eye and potentially other diseases to develop.  It happens with pheasants, partridges, ducks, hens, geese, turkeys et al, so why do we think that it will not happen when very large numbers of grouse live on the same area of moor, over an extended period of time?

Whilst we have found ways of controlling the Strongyle worm (by means of medicated grit and direct dosing), because of the wildness of the grouse’s habitat, the widespread availability of food and often hundreds of natural watering places on the moor, how are we going to be able to treat red grouse that may become infected with a disease such as Coccidiosis, Bulgy Eye or whatever else may come along?  In theory, we could catch up the grouse and dose them, but direct dosing for worms has only been used in adult grouse over the winter when obviously numbers of grouse are much fewer than is the case in the early summer.  It is also a fact that usually, young game birds are more susceptible to disease than older ones. With diseases such as Coccidiosis and possibly others, it seems likely, that they would be at their most effective in terms of killing grouse in July, August and September.  In short, it is probably going to be extremely difficult if not impossible to treat grouse suffering from any disease, let alone reconciling the argument that grouse are a truly wild game bird and do we really want to change that?

The economics of grouse moors are awful and I can well see why owners and keepers want more grouse, more often.  However, unless what has happened with Bulgy Eye is a short-lived one off, we might need to be very careful what we wish for.

Credit: This article appears in the current (Summer) issue of Fieldsports magazine

Mark Osborne - FRICS, FAAV, MBAE

Mark Osborne is founder and Managing Director of JM Osborne & Co. and has been a qualified Chartered Surveyor and Land Agent for over 30 years. He trained on two large traditional landed estates (Chatsworth and Castle Ashby), before s.. Read more.

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