Dr Dave Cowan
speaker
30 appearances
1 recordings
1 series
first heard Dec 2012
last heard Dec 2012
Dr Dave Cowan’s voice in public audio — every appearance, attributed to the second.
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Rats are almost completely commensal in Britain.
So they're associated with human activities.
So that gives us a start.
We only really need to think about how many rats there might be living in close proximity to ourselves.
It's pretty rare, actually.
Certainly in terms of rats being inside our dwellings, it's less than half a percent from the surveys that have been done.
But the better figure to take is actually the number of dwellings that have rats outside.
And there's around 3% of our dwellings have rats present immediately outside dwellings.
We can come up with a figure of about 1.5 million in total.
In Britain, I think, is probably the best way of looking at that.
You need to start with how many commercial premises are there.
There's a figure of about 1.8 million commercial premises in Britain.
And a survey that looked at that suggested that around 5% of those commercial premises had rats present.
But again, each presence was a relatively small number of animals.
So actually, probably the total estimate for the number of rats in and around commercial premises is something like 200,000.
Well, the key one most people think about is rats in sewers.
And this is a bit tricky, but there's an estimate of around 16,000 square kilometres of sewer in Britain.
There's around 5% of the sewers that have rats present.
And from work that was done actually in the 1950s, we had an estimate of around 2,000 per hectare of sewer.
Again, a bit difficult to work that out, but if you multiply those together, you'd end up with a figure of about 1.6 million rats in British sewers.
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