Tuesday, 29 November 2011

WILD BOAR CULL STATISTICS - the proof of mismanagement

It had long been the opinion of photographers that the boar numbers claimed by the Forestry Commission did not match what was being seen within the Forest of Dean. 

A model of population wasn't realised until early 2010 when photographers suddenly began seeing lots of boar, especially mothers with piglets.  It seemed that now everyone was getting photos, whereas pre-2010 it was very definitely a difficult task.  Sightings dropped again by the summer, then late in 2010 and early 2011, something very strange started occurring.  Roadside were being grubbed up like never before and piglets were everywhere.  How had we gone from low numbers of sightings in 2009, with just a modicum of roadside grubbing, to what we were witnessing in early 2011?

The Forestry Commission pounced on this and became ever more insistent that numbers were rising.  They began to cite the roadsides as evidence, as well as begin to publicise cull figures:
April 2008 - April 2009 = 38 animals,
April 2009 - April 2010 = 62 animals,
April 2010 - April 2011 = 122 animals

These were published in the proposed 2011 Management plan along with definitive and unquestionable population numbers. What was interesting was that the numbers culled each year became harder and harder to achieve, until in 2011 the FC announced that they had not achieved their target (150 animals).

Targets were simply calculated by subtracting 90 (a number that the Council wanted to survive) from the FC's total population figure.

On first glance it may appear that increasing numbers of culled boar meant an increasing population.  This also tallied with the ease at which photographers were tracking down the boar from 2010, especially at certain times of year.  But this didn't make sense when the FC could not achieve their cull targets despite the ever rising estimates of total boar - now put at 350 and probably more.  By April 2011 they had killed 122 boars leaving 228 and probably more still roaming.  But 228 boar was about the population size estimated for the previous year (2010) when the FC managed to cull 1 in 4 boar (62/250).

It all became clear when Friends of the Boar were given, via freedom of Information requests, the cull data from the Castlemain depot - the only larder to take culled boar in the Forest of Dean.


Wild Boar cull data 2008 - mid 2011. Click to enlarge.

When the weights of the animals are plotted against time a trend becomes clear of a slow decrease in the average weight (or age) of the population.  In 2008, the average weight was 61kg, but by summer 2011 it was just 41kg.  It had gone from being that of an 18 months old animal to that of a 9 months old animal (a halving of age).

This was the linear trend.  The best fit regression line (shown in red), which tracks some seasonality, predicted even worse to come with a dramatic fall off at the end of the line.

This data was seen by hunting organisations and journalists, with the Guardian in particular very interested.  They contacted scientists and boar experts for their input, with the opinion being that the management of the boar was dangerously flawed and culling is being based upon a poor guess at population.  Many hunters were also outraged at what was occuring.

Our hypothesis was that the FC were now in their second year (at least) of over-culling.  Not by a little bit but decimated by a large margin, which accounted for seasonal difficulties in seeing any boar. 

One problem inherent with over-culling, and the more rapid the worse it is, is the population rebound theory put forward by many mammal ecologists.  It states that sudden increases in nutrition favour stronger mothers and healthier young - youngsters more likely to survive any hardship early in life (cold weather and starvation produce high mortality in natural systems).  What is more, some mammals seem to react to stressful depopulation by actually producing more young in a drastic effort to compensate, and often overcompensate, for the sudden loss of friends and family.  Also, when their young are killed, mothers can come straight back into season to produce yet more young!  Hunting can create a vicious cycle, and promotes the problem that hunting often proposes to solve - over-population.  It is a hunters dream!

The above graph was worrying and we awaited further data to see if the hypothesis remained true.


Wild Boar cull data 2008 - Sept 2011. Click to enlarge.
We shared our findings with the FC in person and in our management plan response in late August with an urgent call to stop culling and implement a closed season.  Rather than consider us, the FC immediately went "all-out" to achieve their cull target in a record breaking time. They also achieved it at the very worst time - when there should have been no killing (closed season).  It appeared personal.  

Their cull target had been achieved this time, and just 6 months. 
April 2011 - September 2011 = 153 animals.

The FC gloated and publicised their achievements everywhere, obviously wanting to be seen as saviours and good managers hoping we would go away proved wrong.  We wrote to the press to highlight at just how belligerent the FC were now acting and what they had just done may prove very serious indeed.

The remaining cull data came in.  Apart from showing an increase in road traffic accidents (due to increased panic from increased hunting? And with those boars being added to the cull target), and killings made disproportionately close to houses and amenity areas, the final data fitted precisely with prediction.  The average age of the boars now stands at just 32kg - a piglet - with stripes!  The red line did not thankfully continue downwards but can now be seen to agree with the linear trend.

Downward spikes can be seen each year.  These represent the onset of killing piglets in late summer.  These piglets belong to first year mothers who typically give birth at this time so as not to compete with the main birthing season in March.  Look carefully and we find that the start of this season has been moving earlier each year.  This is totally consistent with new research from Germany showing how hunting disrupts natural birth patterns (with hunters continuing the myth that boar breed all year round - what they don't say is this only occurs when they are hunted!  This is how game managers farm their animals in order to produce "sustainable" populations.  Farmers also kill newborns or remove them from mothers to increase "productivity").

Look even more carefully at the downward spikes and you see a rising slope with time (2009-2011).  This proves the FC begin killing piglets at dependency (<10kg) and throughout their infancy.  What is more, a higher slope can also been seen (especially 2011) that tracks the growing mothers.  The mothers are now so young when they give birth, they too are still growing quickly.  The parallel lines proves mothers and their piglets are often slaughtered together on purpose (and cannot be welfare cases).  This may be due to 2011 being the year of the tame boar.  The tame sows were young mothers, maybe just 7-8 months old.  The reason they are so young is due entirely to Population or Compensatory Rebound Effect - orphaned piglets come into season much earlier.

Tame boar, road accidents, and boar near to houses (with the assumption many of these were reported by concerned residents to the FC) is probably the reason why the FC managed to achieve their target in half the time (and cheaply too).  Killing boar is getting easier because over-culling is producing younger and less-experienced boar who do not run from humans or roads.  Increased numbers of piglets in early 2011 is now explained, and why they dug up so much of our road verges - they didn't know the dangers yet!

The very strong conclusion is that the FC are mismanaging the boar in a seriously dangerous manner and with belligerence and total disregard for boar welfare.  Compensatory Rebound is definitely in action.  The FC have been given the data but choose to ignore it.

Another conclusion is that the sudden increase in sightings of boar from early 2010 onwards was not a product of more boar, but increasing numbers of sows and their pigets becoming less inclined to run away.  These sows were probably young orphans left to fend alone after their mother was shot.  From 2004 to mid 2009, sighting of little piglets was very rare indeed.   Young mothers were slowly, but surely, created via the compensatory rebound mechanism (earlier fertility) and couldn't pass on any experience to their piglets to run from people (and/or become nocturnal) because there had not been enough time for their own mother to drill this survival strategy home.  This is a trend that has continued to this day.  Why? Because the FC continue to slaughter mothers and young piglets (evidenced in graph, especially for 2011), leaving any surviving piglets to die, or if lucky and fit (which they are in the rebound model), the piglets grow up with little experience of how some humans love to inflict fear and suffering upon wildlife.  This is something that Defra does not give guidance on.

These graphs do not expose a couple of other important underlying issues here, and these will be discussed later in another posting.  Maybe you can work out why digging roadsides always occurs in the Autumn when acorns are at their most plenty?  You may also ponder if these graphs give any insight into the boar NOT in the data, eg poached or organised shooting victims.

We know that Messrs Stannard and Harvey read this blog.  You need to end the hunting culture within your walls and start to manage.  We understand you may be constrained by whatever Defra is telling you, but please study the data again and take note.  There are more important things here than profiteering from the meat sales and inflating the future "value" of the forest to private investors and shooters.  You are very welcome to add your comments below, and maybe we can finally start to work together for the future health of boar and the Forest.

DJS


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