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This post just brings to light matters which become obvious when calculations are made regarding the number of deposits dogs can make in their lifetimes. It doesn't discuss dog fouling statistics regarding quantity as would be expected if weight measurements had been taken.
I have a dog and live in England where the law compels everyone to remove their dogs mess from public places. This includes private land where the public have access. See Controlling your dog in public – 4. Dog fouling and Law & Your Environment – Dog Fouling.
As a dog owner I know it isn't possible to pick up every mess a dog makes. Why? Dogs are not obliged to be on a lead everywhere so sometimes they defecate and it goes unnoticed. Such as:
- in the dark at night (perhaps this is a time to always keep a dog on a lead),
- in deep snow where it melts through and then the snow falls in on top,
- amongst autumn leaves which are the same colour,
- in undergrowth which is difficult to penetrate (fortunately undergrowth guards a mess from others passing by).
This brings me to the point of this post: What proportion of a dogs mess should the owner endeavour to pick up knowing they can't meet a 100% target?
When I first considered this question I thought maybe 99% might be OK. Then I did some calculations.
Calculating Dog Fouling Statistics
Q. How many times does a dog defecate in its lifetime?
The formulae used for this calculation is:
defecations/lifetime = defecations/day × days/year × lifespan
days/year = 365 (leap years are not taken into account here)
In these examples let:
- lifespan = 13 years
- for example 1: defecations/day = 3
- for example 2: defecations/day = 4
So defecations per lifetime:
- for example 1 = 3 × 365 × 13 = 14,223 defecations
- for example 2 = 4 × 365 × 13 = 18,980 defecations
Armed with these results I now put forward four pickup proportion targets for dog owners to consider (defecation values are rounded to the nearest integer for a 13 year period):
|Target||% Picked Up||% Left Behind||Min Number Left Behind||Max Number Left Behind|
Target 1 – A 99% Removal Rate – Poor
From these calculations anyone thinking they will pick up 99% of their dog's mess (because in conversation that sounds like a good proportion) will likely leave behind between 142 and 190 defecations in their dog's lifetime. That is more than 10 per year which could be seen as too many. I think people must aim for a better figure.
Target 2 – A 99.5% Removal Rate – Good
Anyone attempting to pick up 99.5% of their dog's mess will likely leave behind between 71 and 95 defecations in their dog's lifetime. This is only 5 or 7 per year – a good target.
Target 3 – A 99.9% Removal Rate – Excellent
Anyone attempting to pick up 99.9% of their dog's mess will likely leave behind between 14 and 19 defecations in their dog's lifetime. This is only 1 or 2 per year – a very good target.
Target 4 – A 99.99% Removal Rate – Unachievable
I suspect anyone trying to remove 99.99% will find this an impossible target. They would only leave 1 or 2 in their dog's lifetime. I can only see this target being met if a dog is rarely taken out into public space.
I feel the public who don't have dogs might expect dog owners to achieve this target, but that is not realistic. They aren't likely to find those targets met in other parts of their life either and should answer these questions:
- What proportion of litter is picked up by a road sweeper from a town centre?
- What proportion of road surfaces are made pothole free at any one time?
- What proportion of gardens are kept tidy in a residential area?
Conclusion – Choosing A Good Target?
My conclusion after doing these calculations is that dog owners should do better than aim for Target 1 and aim for Target 2 but aspire to Target 3. I don't see Target 4 as achievable.