Yeah, poison is always dangerous to other wildlife, as even if you can avoid them being directly poisoned by the bait, other animals can and will eat the poisoned rat carcasses.
But if you have only seen one rat, you probably don’t need to take any action at all. Rats are very widespread and we are all probably near a rat at any given time, but as you’ve only seen one, it’s likely it was only passing through and you don’t have a rat problem as such. So I wouldn’t be too concerned unless you have a lot more sightings or establish there is a substantial rat colony on or near your property.
