Squirrels are experts at adapting, capable of living almost anywhere, so much so that in some areas they are viewed as pests. Memory and abstract thought are two hallmarks of intelligence that squirrels have proven they are capable of.
Quick Learners
Squirrels are quick studies, capable of learning by observation. In a study performed at the University of Exeter, squirrels would watch another squirrel remove a nut from one of two pots. The squirrels learned quickly that if the squirrel they watched took the nut, the pot would be empty and that going for the opposite pot was the better bet. When having to choose a pot without watching a fellow squirrel first, they showed no preference. Being able to learn by observation is an indicator of abstract thought.