Roe density per km2?

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riverdog

Member
Based on some sketchy, un-scientific dung plot counts and a few back-of-fag-packet calcs I figure a mean roe deer population density to be about 18-24 individuals per km2 in north of england sitka spruce blocks.
To maintain population, are people still looking to cull about 20%, with a weighting to does over bucks?

I was just looking over the South Wark FC cull contract and noticed that the cull target seemed higher than I would have expected for the acreage; are my figures way out? What population densities and cull targets per ha are you people working with?

Thanks.
 

countrryboy

Well-Known Member
Most commercial forestry look for about 5 deer per kmsq. And i think 5% damage over the 1st 5 years to get the grant money paid

We had a reputable company come in and do a deer dung count there estimate/guestimate was +/- 30%, and that was not back of fag packet study, in fact about 30 odd pages of bumf.
 

Mungo

Well-Known Member
I think something has gone wrong with the estimation.

Did you factor in local degradation rate? The most commom cause of over estimates in dung counts is to under estimate how long it takes for dung to degrade.
 

bogtrotter

Well-Known Member
Figure seems very high for the type of ground you mention and you need to cull a third to keep population stable , slightly more does than bucks to keep stable, if you need to decrease the number of resident deer increase the doe cull, the female population is the key to deer numbers.
 

Lupus

Well-Known Member
I've often heard mention of a cull target of 4 per 100Ha for upland forests.

Also worth remembering healthy roe populations produce more twins, so a maintenance cull will be somewhat higher than 20%. A reduction cull, higher still.

Kids are normally born with a 50/50 split for sex, so why the preference for does over bucks in a cull plan other than does being more important regards controlling population productivity? I've always found bucks easier to get than does, so if you shoot your bucks hard you'll often struggle to match that cull with does come winter let alone significantly exceed it.

Wolfie
 

bogtrotter

Well-Known Member
I've often heard mention of a cull target of 4 per 100Ha for upland forests.

Also worth remembering healthy roe populations produce more twins, so a maintenance cull will be somewhat higher than 20%. A reduction cull, higher still.

Kids are normally born with a 50/50 split for sex, so why the preference for does over bucks in a cull plan

Upland forest does will often only produce one kid due to the poorer quality food available.

While its true that roe are born 50/50 sex wise, does are stronger than bucks as in most species and the bucks suffer a higher natural mortality during their first year, by the end of that first year its quite normal for the ratio of these youngsters to be 1.5 does or higher to every buck, hence why doe cull should be higher , as the majority of any cull should be yearlings
 
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pitiliedon

Well-Known Member
sounds high to me, but all ground is different, in large populations mortality can be very high if winter feed is poor,also if you leave younger non territorial does this can supress the survival of calves compared to leaving an older territorial doe . Also If forestry fences are porous and back onto better ground/crop land i would expect a fairly high pop density using the woodland edges. Thermal may help to get a feel for numbers, as will consistent observation in the lamp. There are always more than you are seeing never less and if you go heavy handed for a season or too it will show and you can back off and the pop will bounce back. I think people can get too hung up on numbers and pop models that can never be 100% accurate and at best over time just show historical trends . Depending on what the management is for better to gauge by actual damage or average bodyweights these can give a reasonable impression of density over time . In a reducing population body weights increment up fairly quickly in an increasing pop body weights plateau or drop back. As has been posted already doe,s are the key
 

countrryboy

Well-Known Member
Lot of sense in last 2 or 3 posts.

Sure i read somewhere in theory should be a 60/40 split between sexes culling does heaviest and a roughly 60/40 split (or even higher than 60) for young to old.

Possibly it might be more benefical to measure the habitat state/damage (not really the words i'm looking for, deer impact study1!) know 1 well know stalker would survey the same areas every year and estimate the abundience of certain species the deer eat first. Using quadrats and % abundence scores
They then tied that together with their cull returns and everything else and years of experience to fine tune and tweak any cull plans also looking at future harvesting/planting.
While ur numbrs seem high if ur wood is middle aged to mature with decent grazing allaround that density of deer may be thriving and sustainable, its only when u have young trees roe are a big problem, and u want to start culling heavier before the wood is felled never mind restocked, if numbers very high u want to be culling heavier a bit earlier to get pop down.

But that was back in the day when they had plenty of staff thou, sadly not sure as much of that goes on now and would be dubious about how much emphsis is placed on deer selection nowadays in forestry.
Staff are so thinnly spread and cull targets so high i think an awfull ot are purely chasing numbers and very few will pass up a safe and easyily extractabe shot now
 
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Mungo

Well-Known Member
Kids are normally born with a 50/50 split for sex, so why the preference for does over bucks in a cull plan other than does being more important regards controlling population productivity? I've always found bucks easier to get than does, so if you shoot your bucks hard you'll often struggle to match that cull with does come winter let alone significantly exceed it.

Culls aimed at reducing numbers should target females because a population only requires a tiny proportion of males to ensure all females breed. It's the number of breeding females that determines the recruitment rate.

Take this as an example: you start with a population of 100 deer, with an even sex ratio. You shoot all but one male (and leave all the females). Let's say you manage this by the rut, so at the rut you have a population of 51 deer. Hurrah! Population halved.

But your single male is perfectly capable of mating with every female. This is roe, so they carry twins. 50 does producing 100 fawns. Come the following June, your population is now 151 deer (assuming no mortality). So despite killing all but one male, your population just went UP by 50%.

If you want numbers to come down and stay down, kill the females.
 

caorach

Well-Known Member
Not quite the same thing but in my local area there is a fenced enclosure which was known to hold a population of red deer. The owner brought in a range of experts to do various counts as he was going to replant the area within the fence and wanted the deer removed. They did lots of studying and measuring and so on to come up with a figure of 8 deer in the enclosure. Last I heard they'd shot 32 and were still shooting them. Proxy deer count figures seem to be utter balderdash and I've seen estimates that they are usually wrong by factors of 8 - 16!

For sika deer the observed figure for commercial, mature, Sitka forestry is usually considered to be around 2 deer per square km, for thicket stage replanting it can go as high as 40 - 60 per square km. I think those figures were established from several forests in the south of Scotland. Clearly roe and sika are going to be different but I'd bet the roe density couldn't be much more than the sika value as the limit is likely to be available food and sika can eat a wider range of stuff than roe so this might offset the fact that they probably require more food per day.

Clearly if you have a mixture of mature and thicket stage forestry then the average holding capacity will be much higher than if you just have mature forest plus if there are other clear areas or agricultural land on the boundary then that will also impact upon the figures. Perhaps the projected cull figures are based on the forestry having areas of thicket stage replanting, or perhaps the forest company are planning significant felling in the near future and so the cull figures are based on an anticipated increase in deer density? They may also be looking to reduce deer numbers to as near zero as possible before replanting begins. The satellite images on something like Bing or Google will be helpful to you and the Google Earth Professional application (you need the Professional one for this to work and this is the application and not just running Google in your web browser) for the PC is (or certainly was) available free of charge and it allows you to draw a line around a feature and measure the area - you can use this to measure the area of mature, clear fell and thicket forestry and come up with a round figure for numbers. It isn't science but the figures I get doing this are certainly consistent with the number of deer I see on the ground if you allow that some areas will be more attractive to the deer than others and so on.

My experience with replanted areas indicate that the trees need to get quite big before the local deer density increases and, in fact, the density can be basically zero for maybe 4 - 5 years after replanting. I don't know if this is down to the time it takes the deer population to increase to a level where they leave tradition areas for the "new" areas or whether it takes this long for the ground to become attractive to them and so they chose it over other areas.

I hope that is at least a little help but should highlight that my experience (what it is) is limited to sika. I'd guess that roe have to eat as well and so they will not be radically different from the sika in terms of general trend but there will probably be some variation in the detail.
 

caorach

Well-Known Member
Culls aimed at reducing numbers should target females

Interestingly I was reading the science on this in relation to sika. They did one of those multivariate things that allows you to find the significance of all the various factors and in this case they were looking at the number of deer. It is no surprise to us to hear that the big factor was shooting mature females. What was a little more of a surprise to me (I don't have the book here so can't give actual figures) was that none of the other factors they considered (again can't remember most of them) including shooting calves came any way close to the importance of shooting mature females. I would have imagined as approx. half the calves would be female so that would also be an relatively important factor but its impact was actually vanishingly small.

So not only is targeting mature females the way to go, as common sense would tell you, it is also the case that it is more important than any other factor by such a margin as to make other actions almost worthless in comparison, much more important than common sense would tell you.
 

Mungo

Well-Known Member
Interestingly I was reading the science on this in relation to sika. They did one of those multivariate things that allows you to find the significance of all the various factors and in this case they were looking at the number of deer. It is no surprise to us to hear that the big factor was shooting mature females. What was a little more of a surprise to me (I don't have the book here so can't give actual figures) was that none of the other factors they considered (again can't remember most of them) including shooting calves came any way close to the importance of shooting mature females. I would have imagined as approx. half the calves would be female so that would also be an relatively important factor but its impact was actually vanishingly small.

So not only is targeting mature females the way to go, as common sense would tell you, it is also the case that it is more important than any other factor by such a margin as to make other actions almost worthless in comparison, much more important than common sense would tell you.
I'd be really keen to read that - have you got a reference?

Sadly, I'm on my cell, and typing is a b*tch, but there's a long and fascinating (to me, anyway) conversation to be had on demography. And just how poor most deer managers grasp of it is!
 

Mungo

Well-Known Member
Caorach: re. your point on calves.

Go back to my cartoon roe deer example.

So: you shot all but one male last year. The females all bred. You now have 151 deer. 50 of those are female fawns.

So you now take out all the female fawns. You're still left with all your breeding females.

So come the following spring, you now have your 50 breeding does, one old but happy buck, 50 yearling bucks and ANOTHER 100 fawns.
 

caorach

Well-Known Member
I'd be really keen to read that - have you got a reference?

It came from this book:

http://www.amazon.co.uk/Sika-Deer-Management-Introduced-Populations/dp/4431094288

unfortunately my copy is on loan at the minute, hence why I can't give actual figures, but I must get it back to study it again. I was able to get it second hand (it was actually new in the wrapper when it arrived) for not much cash despite the huge price. Your local library might be able to get it for you as well. All I can say is that if you are interested in sika, or deer in general, then it is well worth a read.

I can't claim to be a deer manager or to have a grasp of anything but some of this stuff is interesting.
 

Hungry hunter

Well-Known Member
The satellite images on something like Bing or Google will be helpful to you and the Google Earth Professional application (you need the Professional one for this to work and this is the application and not just running Google in your web browser) for the PC is (or certainly was) available free of charge and it allows you to draw a line around a feature and measure the area - you can use this to measure the area of mature, clear fell and thicket forestry and come up with a round figure for numbers.

Here's a handy app for measuring distance and area.

https://play.google.com/store/apps/details?id=lt.noframe.fieldsareameasure
 

caorach

Well-Known Member
So come the following spring, you now have your 50 breeding does, one old but happy buck, 50 yearling bucks and ANOTHER 100 fawns.

Again this is a sika figure but I believe the survival rate over a lot of studies was about such that you ended up with about one third the number of calves surviving to 1 year old against the number of breeding hinds. This is less than I imagined as from observation almost every hind seems to have a calf with her and my "impression" of calf survival rate was that it must be close to 100% of the number of breeding hinds. My recollection was that the one third figure was quite robust and applied to a number of very different populations of sika but, again, I don't have the book here so I could be wrong.
 

Mungo

Well-Known Member
Again this is a sika figure but I believe the survival rate over a lot of studies was about such that you ended up with about one third the number of calves surviving to 1 year old against the number of breeding hinds. This is less than I imagined as from observation almost every hind seems to have a calf with her and my "impression" of calf survival rate was that it must be close to 100% of the number of breeding hinds. My recollection was that the one third figure was quite robust and applied to a number of very different populations of sika but, again, I don't have the book here so I could be wrong.
Obviously mortality will change the magnitude of the annual increase, but the basic dynamic is the same.

Mortality only changes the need to target mature females if adult mortality is greater than juvenile mortality. This is very rarely the case in ungulates.
 

Ranger22

Well-Known Member
That would be some population, you'd be tripping over them. I would think a third of your estimation would be nearer the mark. At best population counts are estimates so your never going to get a true picture of the local population. How many times do you go out and see a buck you've never seen before?
 
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