The absence of evidence is not the evidence of absence

We talk to 100’s of customers every month who are suffering from a rat problem and often they come to us when they’ve exhausted all other options and all aspects of their understanding of how they are getting in.

Essentially they’ve reached a dead end with it all and have concluded that they are getting in via osmosis from next doors pond or other such ridiculous theories.

At Pestology we know that every situation can be solved through a logical process of elimination and sound logic will always prevail to see your through to the green fields and blue skies of a rat free existence.

Logic is created once you’ve first established the facts and what we find when we get insight into customers conclusions is that they repeatedly make conclusions where there is no evidence to support these conclusions.

For example, most water authorities such as Thames Water, Southern Water etc. will install bait blocks to a manhole when a customer reports a rat problem.

They will then collect these bait blocks after a week or so and if there are no takes they will conclude ‘no rats in these drains then’.

This is not a sound conclusion.

Firstly drains carry a surprisingly high level of food within them already – congealed grease, rice, food debris from the washing up/dishwasher, slugs, worms and undigested material within human faeces.

In general you wouldn’t believe what people flush down toilets or wash down sinks and all this ends up in the sewers.

Commercial kitchens have huge mascerator pumps to chop up food debris specifically so it can fit down the sink as it speeds up the clean-up process and saves on getting it disposed of elsewhere.

We’ve seen some commercial kitchens disposing of up to 25kg of food debris a day this way!

All of this food is generally highly calorific and already cooked so very digestible and nutritious for the rat.

Much, much tastier compared to a dry block of compressed wheat (which is essentially what bait blocks are) dangled on a wire.

The other consideration is that generally rats are ‘neophobic’ which means ‘fear of anything new’.

They are very in-tune with their environment and will get very suspicious if anything changes about it or is introduced to it.

Behaviours such as this are what keep them alive and they’ve evolved them over millennia  as a result of being down the bottom of the food chain.

So dangling some bait blocks into a sewer is like dropping a worm on a hook into a river – just because nothing eats it does not mean there aren’t any fish!

Generally the rats are like the fish and are simply ignoring it – they just aren’t that stupid as they wouldn’t survive all of life’s other challenges if they were.

Another example is drain surveys – we here all the time, ‘Oh I’ve had one of those, there’s nothing wrong with them – I’ll send you the report so you can see’.

See what exactly we think – some random blokes opinion of what he saw on the camera that day?

Get 5x different drain surveys and you’ll 5x different reports.

There is absolutely nothing conclusive about a drainage report – quite often the one’s we see having missing information, wrong information and/or irrelevant information.

Technology has no inherent intelligence so it doesn’t matter what camera he’s got it’s not going to give him the answer or question anything – he will always have to work it out for himself.

So they are not Ordinance Survey maps – there is no ISO standard to verify their accuracy so don’t take them as gospel (btw OS maps can be wrong too we’ve found, but that’s another blog).

There are many other examples…

Architects diagrams of the extension – we can work from these right?

Nope – doesn’t mean the builder built it like that (any anything like that actually).


Drainage was signed off by building control – must have been fine right?

Nope – don’t know where to start on this but lets just say whatever they check for its not rat related.


Next door say they don’t have rats – they’re nice people so must be true right?

Indeed and they may go to church too but they probably think the noises are birds even though they are under the floor.  Or just think its OK to lie.


There are no droppings in the manholes and I haven’t seen any in there?

Droppings get washed away and the rats aren’t going to look up and wave – don’t expect to lift a manhole lid and then count rats like you’d count cows in a field.

We at Pestology are very careful to establish the facts first with any given rat problem via our initial surveys.

We know that the right information is the foundation for everything that follows and is critical to forming a solid remedial strategy that ultimately solves the problem.

So if you’ve got rats then book your Pestology survey – get new light and sound information on what you thought you already knew!