Psychologists run laboratory rats through mazes and to test their learning abilities. But this example in the wild beats any laboratory experiment.
Rats had nested in a rockery outside my kitchen door. Wanting to move them away to a more comfortable location in the forest, I set up one of those humane rat traps with a trap door, that allows one to catch the rat in a cage and then transport it somewhere.
I baited the cage with muesli (all I had on hand, but I thought it would do the job), and waited.
After a while a baby rat ventured by. It found the entrance to the cage, scrambled in eagerly after the food. It crossed the trap door, and was trapped. Good, I thought, I’ll just finish what I am doing, then take it away somewhere more rat-friendly.
The baby rat meanwhile scrambled around, looking for a way out. After a while it hooked a claw under the trap door, pulled it down and ran out, and back into the rockery.
Damn. I won’t leave it alone in the cage next time, I thought.
Five minutes later the baby rat returned. This time it ran straight up to the trap. In through the entrance. Over the trap door. Picked up some food. Turned around. Hooked a claw under the trap door, pulled it down, and ran out.
That baby rat had learned in just one experience. No experimenters running it through tests time and again. A natural intelligence as good as any human in a similar situation.
(The third time I was ready, and grabbed the cage before it had a chance to escape.)