Rat in a drain.

Rats live predominantly in our sewer system.
They will explore their environment and look for ways to leave the system into our homes.
It is vital that your drains are maintained to ensure rats are unable to leave the sewers.
Rats are curious when it comes to expanding their territory but are very wary when it comes to new objects, you can see here that the rat explores the drains but finds the suspicious bag of rodenticides too risky to entertain.
This rat precedes the rodenticides and is this wary of its presence when it suddenly appears.
The same behavior can be noted with rats around traps, they know the environment and are wary of anything new that gets introduced to it